Engine

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 

Engine: Including Block, Heads, Pistons & Valves

Cooling System: Including Radiator, Thermostat, Water Pump, Heater & Hoses

  

Charging System: Including Alternator, Regulator & Battery

Ignition System: Includes Spark Plugs, Distributor, Ignition Wires & Coil

Automatic Transmissions: Understand the concepts behind what goes on inside these

technological marvels and what goes into repairing them when they fail.  
Brakes: Including Disk & Drum Brakes, Master Cylinder, Power Booster & Anti-lock Brakes Wheel Alignment: With explanations of Caster, Camber, Toe-in along with other angles that

are important to know about. 
Hybrid Power Systems: A detailed look at these new propulsion systems to determine how

they are able to get exceptional fuel economy and equally impressive control over tailpipe emissions. 
Dashboard Gauges: A look at the gauges on your instrument panel and how to read them.

 

Air Conditioner: Including Compressor, Condenser, Evaporator & Receiver Dryer

Electrical Systems: Excellent courses on Electrical Fundamentals, Circuits, Controls and

Electronics  
Fuel System: Includes Carburetor, Fuel Injection, Fuel Pump & Fuel Filter

Emissions System: Including Catalytic converter, Air Pump, Oxygen Sensor, Computer & PCV

Valve  
Battery: A look at how they work and what can go wrong with them.

Starting System: Including the Battery, Starter, Ignition Switch & Neutral Safety Switch.

  

On Board Diagnostics: How Today's Cars Diagnose Themselves The Timing Belt: What They Do, What Happens when they Fail

My car won't start, what should I do? Common no-start problems and what to do about them Here are some good books on Auto Mechanics

A Short Course on
Automobile Engines
by Charles Ofria

Internal combustion gasoline engines run on a mixture of gasoline and air. The ideal mixture is 14.7 parts of air to one part of gasoline (by weight.) Since gas weighs much more than air, we are talking about a whole lot of air and a tiny bit of gas. One part of gas that is completely vaporized into 14.7 parts of air can produce tremendous

power when ignited inside an engine.

Let's see how the modern engine uses that energy to make the wheels turn.

Air enters the engine through the air cleaner and proceeds to the throttle plate. You control the amount of air that passes through the throttle plate and into the engine with the gas pedal. It is then distributed through a series of passages called the intake manifold, to each cylinder. At some point after the air cleaner, depending on the engine, fuel is added to the air-stream by either a fuel injection system or, in older vehicles, by the carburetor.

Once the fuel is vaporized into the air stream, the mixture is drawn into each cylinder as that cylinder begins its intake stroke. When the piston reaches the bottom of the cylinder, the intake valve closes and the piston begins moving up in the cylinder compressing the charge. When the piston reaches the top, the spark plug ignites the fuel-air mixture causing a powerful expansion of the gas, which pushes the piston back down with great force against the crankshaft, just like a bicycle rider pushing against the pedals to make the bike go.

Let's take a closer look at this process.

Engine Types

The majority of engines in motor vehicles today are four-stroke, spark-ignition internal combustion engines. The exceptions like the diesel and rotary engines will not be covered in this article.

There are several engine types which are identified by the number of cylinders and the way the cylinders are laid out. Motor vehicles will have from 3 to 12 cylinders which are arranged in the engine block in several configurations. The most popular of them are shown on the left. In-line engines have their cylinders arranged in a row. 3, 4, 5 and 6 cylinder engines commonly use this arrangement. The "V" arrangement uses two banks of cylinders side-by-side and is commonly used in V-6, V-8, V-10 and V-12 configurations. Flat engines use two opposing banks of cylinders and are less common than the other two designs. They are used in engines from Subaru and Porsche in 4 and 6 cylinder arrangements as well as in the old VW beetles with 4 cylinders. Flat engines are also used in some Ferraris with 12 cylinders

Most engine blocks are made of cast iron or cast aluminum..

Each cylinder contains a piston that travels up and down inside the cylinder bore. All the pistons in the engine are

connected through individual connecting rods to a common crankshaft.

The crankshaft is located below the cylinders on an in-line engine, at the base of the V on a V-type engine and between the cylinder banks on a flat engine. As the pistons move up and down, they turn the crankshaft just like your legs pump up and down to turn the crank that is connected to the pedals of a bicycle.

A cylinder head is bolted to the top of each bank of cylinders to seal the individual cylinders and contain the combustion process that takes place inside the cylinder. Most cylinder heads are made of cast aluminum or cast iron. The cylinder head contains at least one intake valve and one exhaust valve for each cylinder. This allows the air-fuel mixture to enter the cylinder and the burned exhaust gas to exit the cylinder. Engines have at least two valves per cylinder, one intake valve and one exhaust valve. Many newer engines are using multiple intake and exhaust valves per cylinder for increased engine power and efficiency. These engines are sometimes named for the number of valves that they have such as "24 Valve V6" which indicates a V-6 engine with four valves per cylinder. Modern engine designs can use anywhere from 2 to 5 valves per cylinder.

The valves are opened and closed by means of a camshaft. A camshaft is a rotating shaft that has individual lobes for each valve. The lobe is a "bump" on one side of the shaft that pushes against a valve lifter moving it up and down. When the lobe pushes against the lifter, the lifter in turn pushes the valve open. When the lobe rotates away from the lifter, the valve is closed by a spring that is attached to the valve. A common configuration is to have one camshaft located in the engine block with the lifters connecting to the valves through a series of linkages. The camshaft must be synchronized with the crankshaft so that the camshaft makes one revolution for every two revolutions of the crankshaft. In most engines, this is done by a "Timing Chain" (similar to a bicycle chain) that connects the camshaft with the crankshaft. Newer engines have the camshaft located in the cylinder head directly over the valves. This design is more efficient but it is more costly to manufacture and requires multiple camshafts on Flat and V-type engines. It also requires much longer timing chains or timing belts which are prone to wear. Some engines have two camshafts on each head, one for the intake valves and one for the exhaust valves. These engines are called Double Overhead Camshaft (D.O.H.C.) Engines while the other type is called Single Overhead Camshaft (S.O.H.C.) Engines. Engines with the camshaft in the block are called Overhead Valve (O.H.V) Engines.

Now when you see "DOHC 24 Valve V6", you'll know what it means.

How an Engine Works

Since the same process occurs in each cylinder, we will take a look at one cylinder to see how the four stroke process works.

The four strokes are Intake, Compression, Power and Exhaust. The piston travels down on the Intake stroke, up on the Compression stroke, down on the Power stroke and up on the Exhaust stroke.



Intake

As the piston starts down on the Intake stroke, the intake valve opens and the fuel-air mixture is drawn into the cylinder (similar to drawing back the plunger on a hypodermic needle to allow fluid to be drawn into the chamber.) When the piston reaches the bottom of the intake stroke, the intake valve closes, trapping the air-fuel mixture in the cylinder.



Compression

The piston moves up and compresses the trapped air fuel mixture that was brought in by the intake stroke. The amount that the mixture is compressed is determined by the compression ratio of the engine. The compression ratio on the average engine is in the range of 8:1 to 10:1. This means that when the piston reaches the top of the cylinder, the air-fuel mixture is squeezed to about one tenth of its original volume.



Power

The spark plug fires, igniting the compressed air-fuel mixture which produces a powerful expansion of the vapor. The combustion process pushes the piston down the cylinder with great force turning the crankshaft to provide the power to propel the vehicle. Each piston fires at a different time, determined by the engine firing order. By the time the crankshaft completes two revolutions, each cylinder in the engine will have gone through one power stroke.



Exhaust

With the piston at the bottom of the cylinder, the exhaust valve opens to allow the burned exhaust gas to be expelled to the exhaust system. Since the cylinder contains so much pressure, when the valve opens, the gas is expelled with a violent force (that is why a vehicle without a muffler sounds so loud.) The piston travels up to the top of the cylinder pushing all the exhaust out before closing the exhaust valve in preparation for starting the four stroke process over again.

Oiling System

Oil is the life-blood of the engine. An engine running without oil will last about as long as a human without blood. Oil is pumped under pressure to all the moving parts of the engine by an oil pump. The oil pump is mounted at the bottom of the engine in the oil pan and is connected by a gear to either the crankshaft or the camshaft. This way, when the engine is turning, the oil pump is pumping. There is an oil pressure sensor near the oil pump that monitors pressure and sends this information to a warning light or a gauge on the dashboard. When you turn the ignition key on, but before you start the car, the oil light should light, indicating that there is no oil pressure yet, but also letting you know that the warning system is working. As soon as you start cranking the engine to start it, the light should go out indicating that there is oil pressure.

Engine Cooling

Internal combustion engines must maintain a stable operating temperature, not too hot and not too cold. With the massive amounts of heat that is generated from the combustion process, if the engine did not have a method for cooling itself, it would quickly self-destruct. Major engine parts can warp causing oil and water leaks and the oil will boil and become useless.

While some engines are air-cooled, the vast majority of engines are liquid cooled. The water pump circulates coolant throughout the engine, hitting the hot areas around the cylinders and heads and then sends the hot coolant to the radiator to be cooled off. For more information on the cooling system, click here.

Engine Balance

Flywheel A 4 cylinder engine produces a power stroke every half crankshaft revolution, an 8 cylinder, every quarter revolution. This means that a V8 will be smother running than a 4. To keep the combustion pulses from generating a vibration, a flywheel is attached to the back of the crankshaft. The flywheel is a disk that is about 12 to 15 inches in diameter. On a standard transmission car, the flywheel is a heavy iron disk that doubles as part of the clutch system. On automatic equipped vehicles, the flywheel is a stamped steel plate that mounts the heavy torque converter. The flywheel uses inertia to smooth out the normal engine pulses.

Balance Shaft Some engines have an inherent rocking motion that produces an annoying vibration while running. To combat this, engineers employ one or more balance shafts. A balance shaft is a heavy shaft that runs through the engine parallel to the crankshaft. This shaft has large weights that, while spinning, offset the rocking motion of the engine by creating an opposite rocking motion of their own.

A Short Course on Cooling Systems
by Charles Ofria

This article is broken down into four sections:

   

What is a cooling system? How does a cooling system work? The components of a cooling system Cooling system maintenance & Repair

What is a Cooling System?
A typical 4 cylinder vehicle cruising along the highway at around 50 miles per hour, will produce 4000 controlled explosions per minute inside the engine as the spark plugs ignite the fuel in each cylinder to propel the vehicle down the road. Obviously, these explosions produce an enormous amount of heat and, if not controlled, will destroy an engine in a matter of minutes. Controlling these high temperatures is the job of the cooling system.

The modern cooling system has not changed much from the cooling systems in the model T back in the '20s. Oh sure, it has become infinitely more reliable and efficient at doing it's job, but the basic cooling system still consists of liquid coolant being circulated through the engine, then out to the radiator to be cooled by the air stream coming through the front grill of the vehicle.

Today's cooling system must maintain the engine at a constant temperature whether the outside air temperature is 110 degrees Fahrenheit or 10 below zero. If the engine temperature is too low, fuel economy will suffer and emissions will rise. If the temperature is allowed to get too hot for too long, the engine will self destruct.

How Does a Cooling System Work?
Actually, there are two types of cooling systems found on motor vehicles: Liquid cooled and Air cooled. Air cooled engines are found on a few older cars, like the original Volkswagen Beetle, the Chevrolet Corvair and a few others. Many modern motorcycles still use air cooling, but for the most part, automobiles and trucks use liquid cooled systems and that is what this article will concentrate on.

The cooling system is made up of the passages inside the engine block and heads, a water pump to circulate the coolant, a thermostat to control the temperature of the coolant, a radiator to cool the coolant, a radiator cap to control the pressure in the system, and some plumbing consisting of interconnecting hoses to transfer the coolant from the engine to radiator and also to the car's heater system where hot coolant is used to warm up the vehicle's interior on a cold day.

A cooling system works by sending a liquid coolant through passages in the engine block and heads. As the coolant flows through these passages, it picks up heat from the engine. The heated fluid then makes its way through a rubber hose to the radiator in the front of the car. As it flows through the thin tubes in the radiator, the hot liquid is cooled by the air stream entering the engine compartment from the grill in front of the car. Once the fluid is cooled, it returns to the engine to absorb more heat. The water pump has the job of keeping the fluid moving through this system of plumbing and hidden passages.

A thermostat is placed between the engine and the radiator to make sure that the coolant stays above a certain preset temperature. If the coolant temperature falls below this temperature, the thermostat blocks the coolant flow to the radiator, forcing the fluid instead through a bypass directly back to the engine. The coolant will continue to circulate like this until it reaches the design temperature, at which point, the thermostat will open a valve and allow the coolant back through the radiator.

In order to prevent the coolant from boiling, the cooling system is designed to be pressurized. Under pressure, the boiling point of the coolant is raised considerably. However, too much pressure will cause hoses and other parts to burst, so a system is needed to relieve pressure if it exceeds a certain point. The job of maintaining the pressure in the cooling system belongs to the radiator cap. The cap is designed to release pressure if it reaches the specified upper limit that the system was designed to handle. Prior to the '70s, the cap would release this extra pressure to the pavement. Since then, a system was added to capture any released fluid and store it temporarily in a reserve tank. This fluid would then return to the cooling system after the engine cooled down. This is what is called a closed cooling system.

Circulation
The coolant follows a path that takes it from the water pump, through passages inside the engine block where it

collects the heat produced by the cylinders. It then flows up to the cylinder head (or heads in a V type engine) where it collects more heat from the combustion chambers. It then flows out past the thermostat (if the thermostat is opened to allow the fluid to pass), through the upper radiator hose and into the radiator. The coolant flows through the thin flattened tubes that make up the core of the radiator and is cooled by the air flow through the radiator. From there, it flows out of the radiator, through the lower radiator hose and back to the water pump. By this time, the coolant is cooled off and ready to collect more heat from the engine.

The capacity of the system is engineered for the type and size of the engine and the work load that it is expected to undergo. Obviously, the cooling system for a larger, more powerful V8 engine in a heavy vehicle will need considerably more capacity then a compact car with a small 4 cylinder engine. On a large vehicle, the radiator is larger with many more tubes for the coolant to flow through. The radiator is also wider and taller to capture more air flow entering the vehicle from the grill in front.

Antifreeze
The coolant that courses through the engine and associated plumbing must be able to withstand temperatures well below zero without freezing. It must also be able to handle engine temperatures in excess of 250 degrees without boiling. A tall order for any fluid, but that is not all. The fluid must also contain rust inhibiters and a lubricant.

The coolant in today's vehicles is a mixture of ethylene glycol (antifreeze) and water. The recommended ratio is fifty-fifty. In other words, one part antifreeze and one part water. This is the minimum recommended for use in automobile engines. Less antifreeze and the boiling point would be too low. In certain climates where the temperatures can go well below zero, it is permissible to have as much as 75% antifreeze and 25% water, but no more than that. Pure antifreeze will not work properly and can cause a boil over.

Antifreeze is poisonous and should be kept away from people and animals, especially dogs and cats, who are attracted by the sweet taste. Ethylene Glycol, if ingested, will form calcium oxalate crystals in the kidneys which can cause acute renal failure and death.

The Components of a Cooling System
The Radiator  Radiator Cooling Fans Pressure Cap & Reserve Tank  Water Pump  Thermostat  Bypass System






Freeze Plugs Head Gaskets & Intake Manifold Gaskets  Heater Core  Hoses The Radiator



The radiator core is usually made of flattened aluminum tubes with aluminum strips that zigzag between the tubes. These fins transfer the heat in the tubes into the air stream to be carried away from the vehicle. On each end of the radiator core is a tank, usually made of plastic that covers the ends of the radiator,

On most modern radiators, the tubes run horizontally with the plastic tank on either side. On other cars, the tubes run vertically with the tank on the top and bottom. On older vehicles, the core was made of copper and the tanks were brass. The new aluminum-plastic system is much more efficient, not to mention cheaper to produce. On radiators with plastic end caps, there are gaskets between the aluminum core and the plastic tanks to seal the system and keep the fluid from leaking out. On older copper and brass radiators, the tanks were brazed (a form of welding) in order to seal the radiator.

The tanks, whether plastic or brass, each have a large hose connection, one mounted towards the top of the radiator to let the coolant in, the other mounted at the bottom of the radiator on the other tank to let the coolant back out. On the top of the radiator is an additional opening that is capped off by the radiator cap. More on this later.

Another component in the radiator for vehicles with an automatic transmission is a separate tank mounted inside one of the tanks. Fittings connect this inner tank through steel tubes to the automatic transmission. Transmission fluid is piped through this tank inside a tank to be cooled by the coolant flowing past it before returning the the transmission.

Radiator Fans Mounted on the back of the radiator on the side closest to the engine is one or two electric fans inside a housing that is designed to protect fingers and to direct the air flow. These fans are there to keep the air flow going through the radiator while the vehicle is going slow or is stopped with the engine running. If these fans stopped working, every time you came to a stop, the engine temperature would begin rising. On older systems, the fan was connected to the front of the water pump and would spin whenever the engine was running because it was driven by a fan belt instead of an electric motor. In these cases, if a driver would notice the engine begin to run hot in stop and go driving, the driver might put the car in neutral and rev the engine to turn the fan faster which helped cool the engine. Racing the engine on a car with a malfunctioning electric fan would only make things worse because you are producing more heat in the radiator with no fan to cool it off.

The electric fans are controlled by the vehicle's computer. A temperature sensor monitors engine temperature and sends this information to the computer. The computer determines if the fan should be turned on and actuates the fan relay if additional air flow through the radiator is necessary.

If the car has air conditioning, there is an additional radiator mounted in front of the normal radiator. This "radiator" is called the air conditioner condenser, which also needs to be cooled by the air flow entering the engine compartment. You can find out more about the air conditioning condenser by going to our article on Automotive Air Conditioning. As long as the air conditioning is turned on, the system will keep the fan running, even if the engine is not running hot. This is because if there is no air flow through the air conditioning condenser, the air conditioner will not be able to cool the air entering the interior.

Pressure cap and reserve tank
As coolant gets hot, it expands. Since the cooling system is sealed, this expansion causes an increase in pressure in the cooling system, which is normal and part of the design. When coolant is under pressure, the temperature where the liquid begins to boil is considerably higher. This pressure, coupled with the higher boiling point of ethylene glycol, allows the coolant to safely reach temperatures in excess of 250 degrees.

The radiator pressure cap is a simple device that will maintain pressure in the cooling system up to a certain point. If the pressure builds up higher than the set pressure point, there is a spring loaded valve, calibrated to the correct Pounds per Square Inch (psi), to release the pressure.

When the cooling system pressure reaches the point where the cap needs to release this excess pressure, a small amount of coolant is bled off. It could happen during stop and go traffic on an extremely hot day, or if the cooling system is malfunctioning. If it does release pressure under these conditions, there is a system in place to capture the released coolant and store it in a plastic tank that is usually not pressurized. Since there is now less coolant in the system, as the engine cools down a partial vacuum is formed. The radiator cap on these closed systems has a secondary valve to allow the vacuum in the cooling system to draw the coolant back into the radiator from the reserve tank (like pulling the plunger back on a hypodermic needle) There are usually markings on the side of the plastic tank marked Full-Cold, and Full Hot. When the engine is at normal operating temperature, the coolant in the translucent reserve tank should be up to the Full-Hot line. After the engine has been sitting for several hours and is cold to the touch, the coolant should be at the Full-Cold line.

Water Pump
A water pump is a simple device that will keep the coolant moving as long as the engine is running. It is usually mounted on the front of the engine and turns whenever the engine is running. The water pump is driven by the engine through one of the following:



A fan belt that will also be responsible for driving an additional component like an alternator or power steering pump



A serpentine belt, which also drives the alternator, power steering pump and AC compressor among other things.



The timing belt that is also responsible for driving one or more camshafts.

The water pump is made up of a housing, usually made of cast iron or cast aluminum and an impeller mounted on a spinning shaft with a pulley attached to the shaft on the outside of the pump body. A seal keeps fluid from leaking out of the pump housing past the spinning shaft. The impeller uses centrifugal force to draw the coolant in from the lower radiator hose and send it under pressure into the engine block. There is a gasket to seal the water pump to the engine block and prevent the flowing coolant from leaking out where the pump is attached to the block..

Thermostat
The thermostat is simply a valve that measures the temperature of the coolant and, if it is hot enough, opens to allow the coolant to flow through the radiator. If the coolant is not hot enough, the flow to the radiator is blocked and fluid is directed to a bypass system that allows the coolant to return directly back to the engine. The bypass system allows the coolant to keep moving through the engine to balance the temperature and avoid hot spots.

Because flow to the radiator is blocked, the engine will reach operating temperature sooner and, on a cold day, will allow the heater to begin supplying hot air to the interior more quickly.

Since the 1970s, thermostats have been calibrated to keep the temperature of the coolant above 192 to 195 degrees. Prior to that, 180 degree thermostats were the norm. It was found that if the engine is allowed to run at these hotter temperatures, emissions are reduced, moisture condensation inside the engine is quickly burned off extending engine life, and combustion is more complete which improves fuel economy.

The heart of a thermostat is a sealed copper cup that contains wax and a metal pellet. As the thermostat heats up, the hot wax expands, pushing a piston against spring pressure to open the valve and allow coolant to circulate.

The thermostat is usually located in the front, top part of the engine in a water outlet housing that also serves as the connection point for the upper radiator hose. The thermostat housing attaches to the engine, usually with two bolts and a gasket to seal it against leaks. The gasket is usually made of a heavy paper or a rubber O ring is used. In some applications, there is no gasket or rubber seal. Instead, a thin bead of special silicone sealer is squeezed from a tube to form a seal.

There is a mistaken belief by some people that if they remove the thermostat, they will be able to solve hard to find overheating problems. This couldn't be further from the truth. Removing the thermostat will allow uncontrolled circulation of the coolant throughout the system. It is possible for the coolant to move so fast, that it will not be properly cooled as it races through the radiator, so the engine can run even hotter than before under certain conditions. Other times, the engine will never reach its operating temperature. On computer controlled vehicles, the computer monitors engine temperatures and regulates fuel usage based on that temperature. If the engine never reaches operating temperatures, fuel economy and performance will suffer considerably.

Bypass System
This is a passage that allows the coolant to bypass the radiator and return directly back to the engine. Some engines use a rubber hose, or a fixed steel tube. In other engines, there is a cast in passage built into the water pump or front housing. In any case, when the thermostat is closed, coolant is directed to this bypass and channeled back to the water pump, which sends the coolant back into the engine without being cooled by the radiator.

Freeze Plugs
When an engine block is manufactured, a special sand is molded to the shape of the coolant passages in the engine block. This sand sculpture is positioned inside a mold and molten iron or aluminum is poured to form the engine block. When the casting is cooled, the sand is loosened and removed through holes in the engine block

casting leaving the passages that the coolant flows through.

Obviously, if we don't plug up these holes, the

coolant will pour right out.

Plugging these holes is the job of the freeze-out plug. These plugs are steel discs or cups that are press fit in the holes in the side of the engine block and normally last the life of the engine with no problems. But there is a reason they are called freeze-out plugs. In the early days, many people used plain water in their engines, usually after replacing a burst hose or other cooling system repair. "It is summer and I will replace the water with antifreeze when the weather starts turning".

Needless to say, people are forgetful and many a motor suffered the fate of the water freezing inside the block. Often, when this happened the pressure of the water freezing and expanding forced the freeze-out plugs to pop out, relieving the pressure and saving the engine block from cracking. (although, just as often the engine cracked anyway). Another reason for these plugs to fail was the fact that they were made of steel and would easily rust through if the vehicle owner was careless about maintaining the cooling system. Antifreeze has rust inhibitors in the formula to prevent this from happening, but those chemicals would lose their effect after 3 years, which is why antifreeze needs to be changed periodically. The fact that some people left plain water in their engines greatly accelerated the rusting of these freeze plugs.

When a freeze plug becomes so rusty that it perforates, you have a coolant leak that must be repaired by replacing the rusted out freeze plug with a new one. This job ranges from fairly easy to extremely difficult depending on the location of the affected freeze plug. Freeze plugs are located on the sides of the engine, usually 3 or 4 per side. There are also freeze plugs on the back of the engine on some models and also on the heads.

As long as you are good about maintaining the cooling system, you need never worry about these plugs failing on modern vehicles

Head Gaskets and Intake Manifold Gaskets
All internal combustion engines have an engine block and one or two cylinder heads. The mating surfaces where the block and head meet are machined flat for a close, precision fit, but no amount of careful machining will allow them to be completely water tight or be able to hold back combustion gases from escaping past the mating surfaces.

In order to seal the block to the heads, we use a head gasket. The head gasket has several things it needs to seal against. The main thing is the combustion pressure on each cylinder. Oil and coolant must easily flow

between block and head and it is the job of the head gasket to keep these fluids from leaking out or into the combustion chamber, or each other for that matter.

A typical head gasket is usually made of soft sheet metal that is stamped with ridges that surround all leak points. When the head is placed on the block, the head gasket is sandwiched between them. Many bolts, called head bolts are screwed in and tightened down causing the head gasket to crush and form a tight seal between the block and head.

Head gaskets usually fail if the engine overheats for a sustained period of time causing the cylinder head to warp and release pressure on the head gasket. This is most common on engines with cast aluminum heads, which are now on just about all modern engines.

Once coolant or combustion gases leak past the head gasket, the gasket material is usually damaged to a point where it will no longer hold the seal. This causes leaks in several possible areas. For example:

  

combustion gases could leak into the coolant passages causing excessive pressure in the cooling system. coolant could leak into the combustion chamber causing coolant to escape through the exhaust system, often causing a white cloud of smoke at the tailpipe. Other problems such as oil mixing with the coolant or being burned out the exhaust are also possible.

Some engines are more susceptible to head gasket failure than others. I have seen blown head gaskets on engines that just started to overheat and were running hot for less than 5 minutes. The best advice I can give is, if the engine shows signs of overheating, find a place to pull over and shut the engine off as quickly as possible.

Head gaskets themselves are relatively cheap, but it is the labor that's the killer. A typical head gasket replacement is a several hour job where the top part of the engine must be completely disassembled. These jobs can easily reach ,000 or more.

On V type engines, there are two heads, meaning two head gaskets. While the labor won't double if both head gaskets need to be replaced, it will probably add a good 30% more labor to replace both. If only one head gasket has failed, it is usually not necessary to replace both, but it could be added insurance to get them both done at once.

A head gasket replacement begins with the diagnosis that the head gasket has failed. There is no way for a technician to know for certain whether there is additional damage to the cylinder head or other components without first disassembling the engine. All he or she knows is that fluid and/or combustion is not being contained.

One way to tell if a head gasket has failed is through a combustion leak test on the radiator. This is a chemical test that determines if there are combustion gases in the engine coolant. Another way is to remove the spark plugs and crank the engine while watching for water spray from one or more spark plug holes. Once the technician has determined that a head gasket must be replaced, an estimate is given for parts and labor. The technician will then explain that there may be additional charges after the engine is opened if more damage is found.

Heater Core
The hot coolant is also used to provide heat to the interior of the vehicle when needed. This is a simple and straight forward system that includes a heater core, which looks like a small version of a radiator, connected to the cooling system with a pair of rubber hoses. One hose brings hot coolant from the water pump to the heater core and the other hose returns the coolant to the top of the engine. There is usually a heater control valve in one of the hoses to block the flow of coolant into the heater core when maximum air conditioning is called for.

A fan, called a blower, draws air through the heater core and directs it through the heater ducts to the interior of the car. Temperature of the heat is regulated by a blend door that mixes cool outside air, or sometimes air conditioned air with the heated air coming through the heater core. This blend door allows you to control the temperature of the air coming into the interior. Other doors allow you to direct the warm air through the ducts on the floor, the defroster ducts at the base of the windshield, and the air conditioning ducts located in the instrument panel.

Hoses
There are several rubber hoses that make up the plumbing to connect the components of the cooling system. The main hoses are called the upper and lower radiator hoses. These two hoses are approximately 2 inches in diameter and direct coolant between the engine and the radiator. Two additional hoses, called heater hoses, supply hot coolant from the engine to the heater core. These hoses are approximately 1 inch in diameter. One of these hoses may have a heater control valve mounted in-line to block the hot coolant from entering the heater core when the air

conditioner is set to max-cool. A fifth hose, called the bypass hose, is used to circulate the coolant through the engine, bypassing the radiator, when the thermostat is closed. Some engines do not use a rubber hose. Instead, they might use a metal tube or have a built-in passage in the front housing.

These hoses are designed to withstand the pressure inside the cooling system. Because of this, they are subject to wear and tear and eventually may require replacing as part of routine maintenance. If the rubber is beginning to look dry and cracked, or becomes soft and spongy, or you notice some ballooning at the ends, it is time to replace them. The main radiator hoses are usually molded to a shape that is designed to rout the hose around obstacles without kinking. When purchasing replacements, make sure that they are designed to fit the vehicle.

There is a small rubber hose that runs from the radiator neck to the reserve bottle. This allows coolant that is released by the pressure cap to be sent to the reserve tank. This rubber hose is about a quarter inch in diameter and is normally not part of the pressurized system. Once the engine is cool, the coolant is drawn back to the radiator by the same hose.

Cooling System Maintenance and Repair
An engine that is overheating will quickly self destruct, so proper maintenance of the cooling system is very important to the life of the engine and the trouble free operation of the cooling system in general.
The most important maintenance item is to flush and refill the coolant periodically. The reason for this important service is that anti-freeze has a number of additives that are designed to prevent corrosion in the cooling system. This corrosion tends to accelerate when several different types of metal interact with each other. The corrosion causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core. causing the engine to eventually overheat. The anti-corrosion chemicals in the antifreeze prevents this, but they have a limited life span.

Newer antifreeze formulations will last for 5 years or 150,000 miles before requiring replacement. These antifreezes are usually red in color and are referred to as "Extended Life" or "Long Life" antifreeze. GM has been using this type of coolant in all their vehicles since 1996. The GM product is called "Dex-Cool".

Most antifreeze used in vehicles however, is green in color and should be replaced every two years or 30,000 miles, which ever comes first. You can convert to the new long life coolant, but only if you completely flush out all of the old antifreeze. If any green coolant is allowed to mix with the red coolant, you must revert to the shorter replacement cycle.

Look for a shop that can reverse-flush the cooling system. This requires special equipment and the removal of the thermostat in order to do the job properly. This type of flush is especially important if the old coolant looks brown or has scale or debris floating around in it.

If you remove the thermostat for a reverse flush, always replace it with a new thermostat of the proper temperature. It is cheap insurance.

The National Automotive Radiator Service Association (NARSA) recommends that motorists have a seven-point preventative cooling system maintenance check at least once every two years. The seven-point program is designed to identify any areas that need attention. It consists of:

  

a visual inspection of all cooling system components, including belts and hoses a radiator pressure cap test to check for the recommended system pressure level



a thermostat check for proper opening and closing

a pressure test to identify any external leaks to the cooling system parts; including the radiator, water pump, engine coolant passages, radiator and heater hoses and heater core

 

an internal leak test to check for combustion gas leakage into the cooling system



an engine fan test for proper operation

a system power flush and refill with car manufacturer's recommended concentration of coolant

Let's take these items one at a time.

Visual Inspection What you are looking for is the condition of the belts and hoses. The radiator hoses and heater hoses are easily inspected just by opening the hood and looking. You want to be sure that the hoses have no cracking or splitting and that there is no bulging or swelling at the ends. If there is any sign of problems, the hose should be replaced with the correct part number for the year, make and model of the vehicle. Never use a universal hose unless it is an emergency and a proper molded hose is not available.

Heater hoses are usually straight runs and are not molded, so a universal hose is fine to use and often is all that is available. Make sure that you use the proper inside diameter for the hose being replaced. For either the radiator hoses or the heater hoses, make sure that you route the replacement hose in the same way that the original hose was running. Position the hose away from any obstruction that can possibly damage it and always use new hose clamps. After you refill the cooling system with coolant, do a pressure test to make sure that there are no leaks.

On most older vehicles, the water pump is driven by a V belt or serpentine belt on the front of the engine that is also responsible for driving the alternator, power steering pump and air conditioner compressor. These types of belts are easy to inspect and replace if they are worn. You are looking for dry cracking on the inside surface of the belt.

On later vehicles, the water pump is often driven by the timing belt. This belt usually has a specific life expectancy at which time it must be replaced to insure that it does not fail. Since the timing belt is inside the engine and will require partial engine disassembly to inspect, it is very important to replace it at the correct

interval. Since the labor to replace this belt can be significant, it is a good idea to replace the water pump at the same time that the belt is replaced. This is because 90 percent of the labor to replace a water pump has already been done to replace the timing belt. It is simply good insurance to replace the pump while everything is apart.

Radiator pressure cap test A radiator pressure cap is designed to maintain pressure in the cooling system at a certain maximum pressure. If the cooling system exceeds that pressure, a valve in the cap opens to bleed the excessive pressure into the reserve tank. Once the engine has cooled off, a negative pressure begins to develop in the cooling system. When this happens, a second valve in the cap allows the coolant to be siphoned back into the radiator from the reserve tank. If the cap should fail, the engine can easily overheat. A pressure test of the radiator cap is a quick way to tell if the cap is doing its job. It should be able to hold its rated pressure for two minutes. Since radiator caps are quite inexpensive, I would recommend replacing it every 3 years or 36,000 miles, just for added insurance. Make absolutely sure that you replace it with one that is designed for your vehicle.

Thermostat check for proper opening and closing This step is only necessary if you are having problems with the cooling system. A thermostat is designed to open at a certain coolant temperature. To test a thermostat while it is still in the engine, start the engine and let it come to normal operating temperature (do not let it overheat). If it takes an unusually long time for the engine to warm up or for the heater to begin delivering hot air, the thermostat may be stuck in the open position. If the engine does warm up, shut it off and look for the two radiator hoses. These are the two large hoses that go from the engine to the radiator. Feel them carefully (they could be very hot). If one hose is hot and the other is cold, the thermostat may be stuck closed.

If you are having problems and suspect the thermostat, remove it and place it in a pot of water. Bring the water to a boil and watch the thermostat. You should see it open when the water reaches a boil. Most thermostats open at about 195 degrees Fahrenheit. An oven thermometer in the water should confirm that the thermostat is working properly.

Pressure test to identify any external leaks Pressure testing the cooling system is a simple process to determine where a leak is located. This test is only performed after the cooling system has cooled sufficiently to allow you to safely remove the pressure cap. Once you are sure that the cooling system is full of coolant, a cooling system pressure tester is attached in place of the radiator cap. The tester is than pumped to build up pressure in the system. There is a gauge on the tester indicating how much pressure is being pumped. You should pump it to the pressure indicated on the pressure cap or to manufacturer's specs.

Once pressure is applied, you can begin to look for leaks. Also watch the gauge on the tester to see if it loses pressure. If the pressure drops more than a couple of pounds in two minutes, there is likely a leak somewhere that may be hidden. It is not always easy to see where a leak is originating from. It is best to have the vehicle up on a lift so you can look over everything with a shop light or flashlight. If the heater core in leaking, it may not be visible since the core is enclosed and not visible without major disassembly, but one sure sign is the unmistakable odor of antifreeze inside the car. You may also notice the windshield steaming up with an oily residue.

Internal leak test If you are losing coolant, but there are no signs of leaks, you could have a blown head gasket. The best way to test for this problem is with a combustion leak test on the radiator. This is accomplished using a block tester. This is a kit that performs a chemical test on the vapors in the radiator. Blue tester fluid is added to the plastic container on the tester. If the fluid turns yellow during the test, then exhaust gasses are present in the radiator.

The most common causes for exhaust gasses to be present in the radiator is a blown head gasket. Replacing a bad head gasket requires a major disassembly of the engine and can be quite expensive. Other causes include a cracked head or a cracked block, both are even more undesirable than having to replace a head gasket.

When a head gasket goes bad The process of replacing a head gasket begins with completely draining the coolant from the engine. The top part of the engine is then disassembled along with much of the front of the engine in order to gain access to the cylinder heads. The head or heads are then removed and a thorough inspection for additional damage is done.

Before the engine can be reassembled, the mating surfaces of the head and block are first cleaned to make sure that nothing will interfere with the sealing properties of the gasket. The surface of the cylinder head is also checked for flatness and, in some cases, the block is checked as well. The head gasket is then positioned on the block and aligned using locator pegs that are built into the block. The head is then placed on top of the gasket and a number of bolts, called head-bolts are coated with oil and loosely threaded into the assembly. The bolts are then tightened in a specific order to a specified initial torque using a special wrench called a torque wrench. This is to insure that the head gasket is crushed evenly in order to insure a tight seal. This process is then repeated to a second, tighter torque setting, then finally a third torque setting. At this point, the rest of the engine is reassembled and the cooling system is filled with a mixture of antifreeze and water. Once the engine is filled, the technician will pressure test the cooling system to make sure there are no leaks.

In many engines, coolant also passes between the heads and the intake manifold. There are also gaskets for the intake manifold to keep the coolant from leaking out at that point. Replacing an intake manifold gasket is a much easier job than a head gasket, but can still take a couple of hours or more for that job.

Engine Fan Test The radiator cooling fan is an important part of the cooling system operation. While a fan is not really needed while a vehicle is traveling down the highway, it is extremely important when driving slowly or stopped with the

engine running. In the past, the fan was attached to the engine and was driven by the fan belt. The speed of the fan was directly proportional to the speed of the engine. This type of system sometimes caused excessive noise as the car accelerated through the gears. As the engine sped up, a rushing fan noise could be heard. To quiet things down and place less of a drag in the engine, a viscous fan drive was developed in order to disengage the fan when it was not needed.

When computer controls came into being, these engine driven fans gave way to electric fans that were mounted directly on the radiator. A temperature sensor determined when the engine was beginning to run too hot and turned on the fan to draw air through the radiator to cool the engine. On many cars, there were two fans mounted side by side to make sure that the radiator had a uniform air flow for the width of the unit.

When the car was in motion, the speed of the air entering the grill was sufficient to keep the coolant at the proper temperature, so the fans were shut off. When the vehicle came to a stop, there was no natural air flow, so the fan would come on as soon as the engine reached a certain temperature.

If the air conditioner was turned on, a different circuit would come into play. The reason for this is the air conditioning system always requires a good air flow through the condenser mounted in front of the radiator. If the air flow stopped, the air conditioned air coming through the dash outlets would immediately start warming up. For this reason, when the air conditioner is turned on, the fan circuit would power the fans regardless of engine temperature.

If you notice that the engine temperature begins rising soon after the vehicle comes to a stop, the first thing to check is fan operation. If the fan is not turning when the engine is hot, a simple test is to turn the AC on. If the fan begins to work, suspect the temperature sensor in the fan circuit (you will need a wiring diagram for your vehicle to find it). In order to test the fan motor itself, unplug the two wire connector to the fan and connect a 12 volt source to one terminal and ground the other. (it doesn't matter which is which for this test) If the fan motor begins to turn, the motor is good. If it doesn't turn, the motor is bad and must be replaced.

In order to test the system further, you will need a repair manual for the year, make and model vehicle and follow the troubleshooting charts and diagnostic procedures for your vehicle. On most systems, there will be a fan relay or fan control module that can be a trouble spot. There are a number of different control systems, each requiring a different test procedure. Without the proper repair information, you can easily do more harm than good.

Cooling system power flush and refill While you can replace old coolant by draining it out and replacing it with fresh coolant, the best way to properly maintain your cooling system is to have the system power flushed. Power flushing will remove all the old coolant and pull out any sediment and scale along with it.

Power flushing requires a special machine that many auto repair shops have for the purpose. The procedure requires that the thermostat is removed, the lower radiator hose is disconnected, and the flush machine is

connected in line. The lower hose is connected to the machine and the other hose from the machine is connected to the radiator where the lower hose was disconnected from.

Water, and sometimes, a cleaning agent is pumped through the cooling system in a reverse path from the normal coolant flow. This allows any scale to be loosened and flow out. Once clear water is coming out of the system, the hose is reconnected and a new thermostat is installed. Then the cooling system is refilled with the appropriate amount of antifreeze to bring the coolant to the proper mixture of antifreeze and water. For most vehicles and most climates, the mixture is 50 percent antifreeze and 50 percent water. In colder climates, more antifreeze is used, but must never exceed 75 percent antifreeze. Check your owner's manual for the proper procedures and recommendations for your vehicle.

A Short Course on Charging Systems
by Charles Ofria

This article is broken down into six sections:

     

What is a charging system The Alternator The Voltage Regulator Charging system gauge or warning lamp What Can Go Wrong Repairing Charging System Problems

What is a Charging System?
The modern charging system hasn't changed much in over 40 years. It consists of the alternator, regulator (which is usually mounted inside the alternator) and the interconnecting wiring.

The purpose of the charging system is to maintain the charge in the vehicle's battery, and to provide the main source of electrical energy while the engine is running.

If the charging system stopped working, the battery's charge would soon be depleted, leaving the car with a "dead battery." If the battery is weak and the alternator is not working, the engine may not have enough electrical current to fire the spark plugs, so the engine will stop running.

If the battery is "dead", it does not necessarily mean that there is anything wrong with it. It is just depleted of its charge. It can be brought back to life by recharging it with a battery charger, or by running the engine so that the alternator can charge it. For more information on the battery, Click Here

.The main component in the charging system is the ALTERNATOR. The alternator is a generator that produces Alternating Current (AC), similar to the electrical current in your home. This current is immediately converted to Direct Current (DC) inside the alternator. This is because all modern automobiles have a 12 volt, DC electrical system.

A VOLTAGE REGULATOR regulates the charging voltage that the alternator produces, keeping it between 13.5 and 14.5 volts to protect the electrical components throughout the vehicle.

There is also a system to warn the driver if something is not right with the charging system. This could be a dash mounted voltmeter, an ammeter, or more commonly, a warning lamp. This lamp is variously labeled "Gen" Bat" and "Alt.". If this warning lamp lights up while the engine is running, it means that there is a problem in the charging system, usually an alternator that has stopped working. The most common cause is a broken alternator drive belt.

The alternator is driven by a belt that is powered by the rotation of the engine. This belt goes around a pulley connected to the front of the engine's crankshaft and is usually responsible for driving a number of other components including the water pump, power steering pump and air conditioning compressor. On some engines, there is more than one belt and the task of driving these components is divided between them. These belts are usually referred to as: Fan Belt, Alternator Belt, Drive Belt, Power Steering Belt, A/C Belt, etc. More common on late model engines, one belt, called a Serpentine Belt will snake around the front of the engine and drive all the components by itself.

On engines with separate belts for each component, the belts will require periodic adjustments to maintain the proper belt tension. On engines that use a serpentine belt, there is usually a spring loaded belt tensioner that maintains the tension of the belt, so no periodic adjustments are required. A serpentine belt is designed to last around 30,000 miles. Check your owner's manual to see how often yours should be replaced.

Alternator output is measured in both voltage and amperage. To understand voltage and amperage, you must also know about resistance, which is measured in ohms. An easy way to picture this is to compare the movement of electricity to that of running water. Water flows through a pipe with a certain amount of pressure. The size (diameter) of the pipe dictates how much resistance there will be to the flowing water. The smaller the pipe, the more resistance. You can increase the pressure to get more water to flow through, or you can increase the size of the pipe to allow more water to flow using less pressure. Since too much pressure can burst the pipe, we

should probably restrict the amount of pressure being used. You get the idea, but how is this related to the flow of electricity?

Well, voltage is the same as water pressure. Amperage is like the amount or volume of water flowing through, while resistance is the size of the wire transmitting the current. Since too much voltage will damage the electrical components such as light bulbs and computer circuits, we must limit the amount of voltage. This is the job of the voltage regulator. Too much water pressure and things could start breaking. Too much voltage and things could start burning out.

Let's get technical
Now, let's go a little deeper and see how these charging system components actually work to produce the electrical power that a modern automobile requires.

The Alternator
The alternator uses the principle of electromagnetism to produce current. The way this works is simple. If you take a strong magnet and pass it across a wire, that wire will generate a small voltage. Take that same wire and loop it many times, than if you pass the same magnet across the bundle of loops, you create a more sizable voltage in that wire.

There are two main components that make up an alternator. They are the rotor and the stator. The rotor is connected directly to the alternator pulley. The drive belt spins the pulley, which in turn spins the rotor. The stator is mounted to the body of the alternator and remains stationary. There is just enough room in the center of the stator for the rotor to fit and be able to spin without making any contact.

The stator contains 3 sets of wires that have many loops each and are evenly distributed to form a three phase system. On some systems, the wires are connected to each other at one end and are connected to a rectifier assembly on the other end. On other systems, the wires are connected to each other end to end, and at each of the three connection points, there is also a connection to the rectifier. More on what a rectifier is later.

The rotor contains the powerful magnet that passes close to the many wire loops that make up the stator. The magnets in the rotor are actually electro magnets, not a permanent magnets.

This is done so that we can control how much voltage the alternator produces by regulating the amount of current that creates the magnetic field in the rotor. In this way, we can control the output of the alternator to suit our needs, and protect the circuits in the automobile from excessive voltage.

Now we know that every magnet has a north and a south pole and electro magnets are no exception. Our rotor has two interlocking sections of electro magnets that are arranged so that there are fingers of alternating north and south poles. that are evenly distributed on the outside of the rotor.

When we spin the rotor inside the stator and apply current to the rotor through a pair of brushes that make constant contact with two slip rings on the rotor shaft. This causes the rotor to become magnetized. The alternating north and south pole magnets spin past the three sets of wire loops in the stator and produce a constantly reversing voltage in the three wires. In other words, we are producing alternating current in the stator.

Now, we have to convert this alternating current to direct current current. This is done by using a series of 6 diodes that are mounted in a rectifier assembly. A diode allows current to flow only in one direction. If voltage tries to flow in the other direction, it is blocked. The six diodes are arranged so that all the voltage coming from the alternator is aligned in one direction thereby converting AC current into DC current.

There are 2 diodes for each of the three sets of windings in the stator. The two diodes are facing in opposite directions, one with its north pole facing the windings and the other with its south pole facing the windings. This arrangement causes the AC current coming out of the windings to be converted to DC current before it leaves the alternator through the B terminal. Connected to the B terminal of the alternator is a fairly heavy wire that runs straight to the battery.

Current to generate the magnetic field in the rotor comes from the ignition switch and passes through the voltage regulator. Since the rotor is spinning, we need a way to connect this current from the regulator to the spinning rotor. This is accomplished by wires connected to two spring loaded brushes that rub against two slip rings on the rotor's shaft. The voltage regulator monitors the voltage coming out of the alternator and, when it reaches a

threshold of about 14.5 volts, the regulator reduces the current in the rotor to weaken the magnetic field. When the voltage drops below this threshold, the current to the rotor is increased.

There is another circuit in the alternator to control the charging system warning lamp that is on the dash. Part of that circuit is another set of diodes mounted inside the alternator called the diode trio. The diode trio takes current coming from the three stator windings and passes a small amount through three diodes so that only the positive voltage comes through. After the diodes, the wires are joined into one wire and sent out of the alternator at the L connection. It then goes to one side of the dash warning lamp that is used to tell you when there is a problem with the charging system. The other side of the lamp is connected to the run side of the ignition switch. If both sides of the warning lamp have equal positive voltage, the lamp will not light. Remove voltage from one side and the lamp comes on to let you know there is a problem.

This system is not very efficient. There are many types of malfunctions of the charging system that it cannot detect, so just because the lamp is not lit does not mean everything is ok. A volt meter is probably the best method of determining whether the charging system is working properly

The Voltage Regulator
The voltage regulator can be mounted inside or outside of the alternator housing. If the regulator is mounted outside (common on some Ford products) there will be a wiring harness connecting it to the alternator.

The voltage regulator controls the field current applied to the spinning rotor inside the alternator. When there is no current applied to the field, there is no voltage produced from the alternator. When voltage drops below 13.5 volts, the regulator will apply current to the field and the alternator will start charging. When the voltage exceeds 14.5 volts, the regulator will stop supplying voltage to the field and the alternator will stop charging. This is how voltage output from the alternator is regulated. Amperage or current is regulated by the state of charge of the battery. When the battery is weak, the electromotive force (voltage) is not strong enough to hold back the current from the alternator trying to recharge the battery. As the battery reaches a state of full charge, the electromotive force becomes strong enough to oppose the current flow from the alternator, the amperage output from the alternator will drop to close to zero, while the voltage will remain at 13.5 to 14.5. When more electrical power is used, the electromotive force will reduce and alternator amperage will increase. It is extremely important that when alternator efficiency is checked, both voltage and amperage outputs are checked. Each alternator has a rated amperage output depending on the electrical requirements of the vehicle.

Charging system gauge or warning lamp
The charging system gauge or warning lamp monitors the health of the charging system so that you have a warning of a problem before you get stuck.

When a charging problem is indicated, you can still drive a short distance to find help unlike an oil pressure or coolant temperature problem which can cause serious engine damage if you continue to drive. The worst that can happen with a charging system problem is that you get stuck in a bad location.

A charging system warning lamp is a poor indicator of problems in that there are many charging problems that it will not recognize. If it does light while you are driving, it usually means the charging system is not working at all. The most common cause of this is a broken alternator belt.

There are two types of gauges used to monitor charging systems on some vehicles: a voltmeter which measures system voltage and an ammeter which measures amperage. Most modern cars that have gauges use a voltmeter because it is a much better indicator of charging system health. A mechanic's voltmeter is usually the first tool a technician uses when checking out a charging system

A modern automobile has a 12 volt electrical system. A fully charged battery will read about 12.5 volts when the engine is not running. When the engine is running, the charging system takes over so that the voltmeter will read 14 to 14.5 volts and should stay there unless there is a heavy load on the electrical system such as wipers, lights, heater and rear defogger all operating together while the engine is idling at which time the voltage may drop. If the voltage drops below 12.5, it means that the battery is providing some of the current. You may notice that your dash lights dim at this point. If this happens for an extended period, the battery will run down and may not have enough of a charge to start the car after shutting it off. This should never happen with a healthy charging system because as soon as you step on the gas, the charging system will recharge the battery. If the voltage is constantly below 14 volts, you should have the system checked. If the voltage ever goes above 15 volts, there is a problem with the voltage regulator. Have the system checked as soon as possible as this "overcharging" condition can cause damage to your electrical system.

If you think of electricity as water, voltage is like water pressure, whereas amperage is like the volume of water. If you increase pressure, then more water will flow through a given size pipe, but if you increase the size of the pipe, more water will flow at a lower pressure. An ammeter will read from a negative amperage when the battery is providing most of the current thereby depleting itself, to a positive amperage if most of the current is coming from the charging system. If the battery is fully charged and there is minimal electrical demand, then the ammeter should read close to zero, but should always be on the positive side of zero. It is normal for the ammeter to read a high positive amperage in order to recharge the battery after starting, but it should taper off in a few minutes. If it continues to read more than 10 or 20 amps even though the lights, wipers and other electrical devices are turned off, you may have a weak battery and should have it checked.

What can go wrong?

There are a number of things that can go wrong with a charging system:



Insufficient Charging Output If one of the three stator windings failed, the alternator would still charge, but only at two thirds of its normal output. Since an alternator is designed to handle all the power that is needed under heavy load conditions, you may never know that there is a problem with the unit. It might only become apparent on a dark, cold rainy night when the lights, heater, windshield wipers and possible the seat heaters and rear defroster are all on at once that you may notice the lights start to dim as you slow down. If two sets of windings failed, you will probably notice it a lot sooner

It is more common for one or more of the six diodes in the rectifier to fail. If a diode burns out and opens one of the circuits, you would see the same problem as if one of the windings had failed. The alternator will run at a reduced output. However, if one of the diodes were to short out and allow current to pass in either direction, other problems will occur. A shorted diode will allow AC current to pass through to the automobile's electrical system which can cause problems with the computerized sensors and processors. This condition can cause the car to act unpredictably and cause all kinds of problems.



Too much voltage A voltage regulator is designed to limit the voltage output of an alternator to 14.5 volts or less to protect the vehicle's electrical system. If the regulator malfunctions and allows uncontrolled voltage to be released, you will see bulbs and other electrical components begin to fail. This is a dangerous and potentially costly problem. Fortunately, this type of failure is very rare. Most failures cause a reduction of voltage or amperage.



Noise Since the rotor is always spinning while the engine is running, there needs to be bearings to support the shaft and allow it to spin freely. If one of those bearings were to fail, you will hear a grinding noise coming from the alternator. A mechanic's stethoscope can be used to confirm which of the spinning components driven by the serpentine belt is making the noise.

Repairing Charging System Problems
The most common repair is the replacement of the alternator with a new or rebuilt one. A properly rebuilt alternator is as good as a new alternator and can cost hundreds less than purchasing a brand new one.

Labor time to replace an alternator is typically under an hour unless your alternator is in a hard to access location. Most alternators are easily accessible and visible on the top of the engine.

Replacing an alternator is usually an easy task for a backyard mechanic and rebuilt alternators are readily available for most vehicles at the local auto parts store. The most important task for the do-it-yourselfer is to be

careful not to short anything out. ALWAYS DISCONNECT THE BATTERY BEFORE REPLACING AN ALTERNATOR.

Alternators can be repaired by a knowledgeable technician, but in most cases, it is not economical to do this. Also, since the rest of the alternator is not touched, a repair job is usually not guaranteed.

In some cases, if the problem is diagnosed as a bad voltage regulator, the regulator can be replaced without springing for a complete rebuild. The problem with this is that there will be an extra labor charge for disassembling the alternator in order to get to the internal regulator. That extra cost, along with the cost of the replacement regulator, will bring the total cost close to the cost of a complete (and guaranteed) rebuilt.

This is not the case when the regulator is not inside the alternator. In those cases, the usual practice is to just replace the part that is bad.

A Short Course on Ignition Systems:
by Charles Ofria

The purpose of the ignition system is to create a spark that will ignite the fuel-air mixture in the cylinder of an engine. It must do this at exactly the right instant and do it at the rate of up to several thousand times per minute for each cylinder in the engine. If the timing of that spark is off by a small fraction of a second, the engine will run poorly or not run at all. To learn more about how an engine works, go to our Short Course on Automobile Engines.

The ignition system sends an extremely high voltage to the spark plug in each cylinder when the piston is at the top of its compression stroke. The tip of each spark plug contains a gap that the voltage must jump across in order to reach ground. That is where the spark occurs.

The voltage that is available to the spark plug is somewhere between 20,000 volts and 50,000 volts or better. The job of the ignition system is to produce that high voltage from a 12 volt source and get it to each cylinder in a specific order, at exactly the right time.

Let's see how this is done.

The ignition system has two tasks to perform. First, it must create a voltage high enough (20,000+) to arc across the gap of a spark plug, thus creating a spark strong enough to ignite the air/fuel mixture for combustion. Second, it must control the timing of that the spark so it occurs at the exact right time and send it to the correct cylinder.

The ignition system is divided into two sections, the primary circuit and the secondary circuit. The low voltage primary circuit operates at battery voltage (12 to 14.5 volts) and is responsible for generating the signal to fire the spark plug at the exact right time and sending that signal to the ignition coil. The ignition coil is the component that converts the 12 volt signal into the high 20,000+ volt charge. Once the voltage is stepped up, it goes to the secondary circuit which then directs the charge to the correct spark plug at the right time.

The Basics
Before we begin this discussion, let's talk a bit about electricity in general. I know that this is basic stuff, but there was a time that you didn't know about this and there are people who need to know the basics so that they could make sense of what follows.

All automobiles work on DC, or Direct Current. This means that current moves in one direction, from the positive battery terminal to the negative battery terminal. In the case of the automobile, the negative battery terminal is connected by a heavy cable directly to the body and the engine block of the vehicle. The body and any metal component in contact with it is called the Ground. This means that a circuit that needs to send current back to the negative side of the battery can be connected to any part of the vehicle's metal body or the metal engine block.

A good example to see how this works is the headlight circuit. The headlight circuit consists of a wire that goes from the positive battery terminal to the headlight switch. Another wire goes from the headlight switch to one of two terminals on the headlamp bulb. Finally, a third wire goes from a second terminal on the bulb to the metal body of the car. When you switch the headlights on, you are connecting the wire from the battery with the wire to the headlamps allowing battery current to go directly to the headlamp bulbs. Electricity passes through the filaments inside the bulb, then out the other wire to the metal body. From there, the current goes back to the negative terminal of the battery completing the circuit. Once the current is flowing through this circuit, the filament inside the headlamp gets hot and glows brightly. Let there be light.

Now, back to the ignition system. The basic principle of the electrical spark ignition system has not changed for over 75 years. What has changed is the method by which the spark is created and how it is distributed.

Currently, there are three distinct types of ignition systems, The Mechanical Ignition System was used prior to 1975. It was mechanical and electrical and used no electronics. By understanding these early systems, it will be easier to understand the new electronic and computer controlled ignition systems, so don't skip over it. The Electronic Ignition System started finding its way to production vehicles during the early '70s and became popular when better control and improved reliability became important with the advent of emission controls. Finally, the Distributorless Ignition System became available in the mid '80s. This system was always computer controlled and contained no moving parts, so reliability was greatly improved. Most of these systems required no maintenance except replacing the spark plugs at intervals from 60,000 to over 100,000 miles.

Let's take a detailed look at each system and see how they work.

The Mechanical Ignition System
(from the dawn of the automobile to 1974)

The distributor is the nerve center of the mechanical ignition system and has two tasks to perform. First, it is responsible for triggering the ignition coil to generate a spark at the precise instant that it is required (which varies depending how fast the engine is turning and how much load it is under). Second, the distributor is responsible for directing that spark to the proper cylinder (which is why it is called a distributor)

The circuit that powers the ignition system is simple and straight forward. (see above) When you insert the key in the ignition switch and turn the key to the Run position, you are sending current from the battery through a wire directly to the positive (+) side of the ignition coil. Inside the coil is a series of copper windings that loop around the coil over a hundred times before exiting out the negative (-) side of the coil. From there, a wire takes this current over to the distributor and is connected to a special on/off switch, called the points. When the points are closed, this current goes directly to ground. When current flows from the ignition switch, through the windings in the coil, then to ground, it builds a strong magnetic field inside the coil.

The points are made up of a fixed contact point that is fastened to a plate inside the distributor, and a movable contact point mounted on the end of a spring loaded arm.. The movable point rides on a 4,6, or 8 lobe cam (depending on the number of cylinders in the engine) that is mounted on a rotating shaft inside the distributor. This distributor cam rotates in time with the engine, making one complete revolution for every two revolutions of the engine. As it rotates, the cam pushes the points open and closed. Every time the points open, the flow of current is interrupted through the coil, thereby collapsing the magnetic field and releasing a high voltage surge through the secondary coil windings. This voltage surge goes out the top of the coil and through the high-tension coil wire.

Now, we have the voltage necessary to fire the spark plug, but we still have to get it to the correct cylinder. The coil wire goes from the coil directly to the center of the distributor cap. Under the cap is a rotor that is mounted on top of the rotating shaft. The rotor has a metal strip on the top that is in constant contact with the center terminal of the distributor cap. It receives the high voltage surge from the coil wire and sends it to the other end of the rotor which rotates past each spark plug terminal inside the cap. As the rotor turns on the shaft, it sends the voltage to the correct spark plug wire, which in turn sends it to the spark plug. The voltage enters the spark plug at the terminal at the top and travels down the core until it reaches the tip. It then jumps across the gap at the tip of the spark plug, creating a spark suitable to ignite the fuel-air mixture inside that cylinder.

The description I just provided is the simplified version, but should be helpful to visualize the process, but we left out a few things that make up this type of ignition system. For instance, we didn't talk about the condenser that is connected to the points, nor did we talk about the system to advance the timing. Let's take a look at each section and explore it in more detail.

The ignition switch. There are two separate circuits that go from the ignition switch to the coil. One circuit runs through a resistor in

order to step down the voltage about 15% in order to protect the points from premature wear. The other circuit sends full battery voltage to the coil. The only time this circuit is used is during cranking. Since the starter draws a considerable amount of current to crank the engine, additional voltage is needed to power the coil. So when the key is turned to the spring-loaded start position, full battery voltage is used. As soon as the engine is running, the driver releases the key to the run position which directs current through the primary resistor to the coil.

On some vehicles, the primary resistor is mounted on the firewall and is easy to replace if it fails. On other vehicles, most notably vehicles manufactured by GM, the primary resistor is a special resistor wire and is bundled in the wiring harness with other wires, making it more difficult to replace, but also more durable.

The Distributor When you remove the distributor cap from the top of the distributor, you will see the points and condenser. The condenser is a simple capacitor that can store a small amount of current. When the points begin to open, the current flowing through the points looks for an alternative path to ground. If the condenser were not there, it would try to jump across the gap of the points as they begin to open. If this were allowed to happen, the points would quickly burn up and you would hear heavy static on the car radio. To prevent this, the condenser acts like a path to ground. It really is not, but by the time the condenser is saturated, the points are too far apart for the small amount of voltage to jump across the wide point gap. Since the arcing across the opening points is eliminated, the points last longer and there is no static on the radio from point arcing.

The points require periodic adjustments in order to keep the engine running at peek efficiency. This is because there is a rubbing block on the points that is in contact with the cam and this rubbing block wears out over time changing the point gap. There are two ways that the points can be measured to see if they need an adjustment. One way is by measuring the gap between the open points when the rubbing block is on the high point of the cam. The other way is by measuring the dwell electrically. The dwell is the amount, in degrees of cam rotation, that the points stay closed.

On some vehicles, points are adjusted with the engine off and the distributor cap removed. A mechanic will loosen the fixed point and move it slightly, then retighten it in the correct position using a feeler gauge to measure the gap. On other vehicles, most notably GM cars, there is a window in the distributor where a mechanic can insert a tool and adjust the points using a dwell meter while the engine is running. Measuring dwell is much more accurate than setting the points with a feeler gauge.

Points have a life expectancy of about 10,000 miles at which time they have to be replaced. This is done during a routine major tune up. During the tune up, points, condenser, and the spark plugs are replaced, the timing is set and the carburetor is adjusted. In some cases, to keep the engine running efficiently, a minor tune up would be performed at 5,000 mile increments to adjust the points and reset the timing.

Ignition Coil

The ignition coil is nothing more that an electrical transformer. It contains both primary and secondary winding circuits. The coil primary winding contains 100 to 150 turns of heavy copper wire. This wire must be insulated so that the voltage does not jump from loop to loop, shorting it out. If this happened, it could not create the primary magnetic field that is required. The primary circuit wire goes into the coil through the positive terminal, loops around the primary windings, then exits through the negative terminal. The coil secondary winding circuit contains 15,000 to 30,000 turns of fine copper wire, which also must be insulated from each other. The secondary windings sit inside the loops of the primary windings. To further increase the coils magnetic field the windings are wrapped around a soft iron core. To withstand the heat of the current flow, the coil is filled with oil which helps keep it cool. The ignition coil is the heart of the ignition system. As current flows through the coil a strong magnetic field is built up. When the current is shut off, the collapse of this magnetic field to the secondary windings induces a high voltage which is released through the large center terminal. This voltage is then directed to the spark plugs through the distributor.
Ignition Timing The timing is set by loosening a hold-down screw and rotating the body of the distributor. Since the spark is triggered at the exact instant that the points begin to open, rotating the distributor body (which the points are mounted on) will change the relationship between the position of the points and the position of the distributor cam, which is on the shaft that is geared to the engine rotation.

While setting the initial, or base timing is important, for an engine to run properly, the timing needs to change depending on the speed of the engine and the load that it is under. If we can move the plate that the points are mounted on, or we could change the position of the distributor cam in relation to the gear that drives it, we can alter the timing dynamically to suit the needs of the engine.

Why do we need the timing to advance when the engine runs faster? When the spark plug fires in the combustion chamber, it ignites whatever fuel and air mixture is present at the tip

of the spark plug. The fuel that surrounds the tip is ignited by the burning that was started by the spark plug, not by the spark itself. That flame front continues to expand outward at a specific speed that is always the same, regardless of engine speed. It does not begin to push the piston down until it fills the combustion chamber and has no where else to go. In order to maximize the amount of power generated, the spark plug must fire before the piston reaches the top of the cylinder so that the burning fuel is ready to push the piston down as soon as it is at the top of its travel. The faster the engine is spinning, the earlier we have to fire the plug to produce maximum power.

There are two mechanisms that allow the timing to change: Centrifugal Advance and Vacuum Advance.

Centrifugal Advance changes the timing in relation to the speed (RPM) of the engine. It uses a pair of weights that are connected to the spinning distributor shaft. These weights are hinged on one side to the lower part of the shaft and connected by a linkage to the upper shaft where the distributor cam is. The weights are held close to the shaft be a pair of springs. As the shaft spins faster, the weights are pulled out by centrifugal force against the spring pressure. The faster the shaft spins, the more they are pulled out. When the weights move out, it changes the alignment between the lower and upper shaft, causing the timing to advance.

Vacuum Advance works by changing the position of the points in relationship to the distributor body. An engine produces vacuum while it is running with the throttle closed. In other words, your foot is off the gas pedal. In this configuration, there is very little fuel and air in the combustion chamber.

Vacuum advance uses a vacuum diaphragm connected to a link that can move the plate that the points are mounted on. By sending engine vacuum to the vacuum advance diaphragm, timing is advanced. On older cars, the vacuum that is used is port vacuum, which is just above the throttle plate. With this setup, there is no vacuum present at the vacuum advance diaphragm while the throttle is closed. When the throttle is cracked opened, vacuum is sent to the vacuum advance, advancing the timing.

On early emission controlled vehicles, manifold vacuum was used so that vacuum was present at the vacuum advance at idle in order to provide a longer burn time for the lean fuel mixtures on those engines. When the throttle was opened, vacuum was reduced causing the timing to retard slightly. This was necessary because as the throttle opened, more fuel was added to the mixture reducing the need for excessive advance. Many of these early emission controlled cars had a vacuum advance with electrical components built into the advance unit to modify the timing under certain conditions.

Both Vacuum and Centrifugal advance systems worked together to extract the maximum efficiency from the engine. If either system was not functioning properly, both performance and fuel economy would suffer. Once computer controls were able to directly control the engine's timing, vacuum and centrifugal advance mechanisms were no longer necessary and were eliminated.

Ignition Wires These cables are designed to handle 20,000 to more than 50,000 volts, enough voltage to toss you across the room if you were to be exposed to it. The job of the spark plug wires is to get that enormous power to the spark plug without leaking out. Spark plug wires have to endure the heat of a running engine as well as the extreme changes in the weather. In order to do their job, spark plug wires are fairly thick, with most of that thickness devoted to insulation with a very thin conductor running down the center. Eventually, the insulation will succumb to the elements and the heat of the engine and begins to harden, crack, dry out, or otherwise break down. When that happens, they will not be able to deliver the necessary voltage to the spark plug and a misfire will occur. That is what is meant by "Not running on all cylinders". To correct this problem, the spark plug wires would have to be replaced.

Spark plug wires are routed around the engine very carefully. Plastic clips are often used to keep the wires separated so that they do not touch together. This is not always necessary, especially when the wires are new, but as they age, they can begin to leak and crossfire on damp days causing hard starting or a rough running engine.

Spark plug wires go from the distributor cap to the spark plugs in a very specific order. This is called the "firing order" and is part of the engine design. Each spark plug must only fire at the end of the compression stroke. Each cylinder has a compression stroke at a different time, so it is important for the individual spark plug wire to be routed to the correct cylinder.

For instance, a popular V8 engine firing order is 1, 8, 4, 3, 6, 5, 7, 2. The cylinders are numbered from the front to the rear with cylinder #1 on the front-left of the engine. So the cylinders on the left side of the engine are numbered 1, 3, 5, 7 while the right side are numbered 2, 4, 6, 8. On some engines, the right bank is 1, 2, 3, 4 while the left bank is 5, 6, 7, 8. A repair manual will tell you the correct firing order and cylinder layout for a particular engine.

The next thing we need to know is what direction the distributor is rotating in, clockwise or counter-clockwise, and which terminal on the distributor cap that #1 cylinder is located. Once we have this information, we can begin routing the spark plug wires.

If the wires are installed incorrectly, the engine may backfire, or at the very least, not run on all cylinders. It is very important that the wires are installed correctly.

Spark Plugs The ignition system's sole reason for being is to service the spark plug. It must provide sufficient voltage to jump the gap at the tip of the spark plug and do it at the exact right time, reliably on the order of thousands of times per minute for each spark plug in the engine.

The modern spark plug is designed to last many thousands of miles before it requires replacement. These electrical wonders come in many configurations and heat ranges to work properly in a given engine.

The heat range of a spark plug dictates whether it will be hot enough to burn off any residue that collects on the tip, but not so hot that it will cause pre-ignition in the engine. Pre-ignition is caused when a spark plug is so hot, that it begins to glow and ignite the fuel-air mixture prematurely, before the spark. Most spark plugs contain a resistor to suppress radio interference. The gap on a spark plug is also important and must be set before the spark plug is installed in the engine. If the gap is too wide, there may not be enough voltage to jump the gap, causing a misfire. If the gap is too small, the spark may be inadequate to ignite a lean fuel-air mixture, also causing a misfire.

The Electronic Ignition System
(from 1970's to today)

This section will describe the main differences between the early point & condenser systems and the newer electronic systems. If you are not familiar with the way an ignition system works in general, I strongly recommend that you first read the previous section The Mechanical Ignition System.

In the electronic ignition system, the points and condenser were replaced by electronics. On these systems, there were several methods used to replace the points and condenser in order to trigger the coil to fire. One method used a metal wheel with teeth, usually one for each cylinder. This is called an armature or reluctor. A magnetic pickup coil senses when a tooth passes and sends a signal to the control module to fire the coil.

Other systems used an electric eye with a shutter wheel to send a signal to the electronics that it was time to trigger the coil to fire. These systems still need to have the initial timing adjusted by rotating the distributor housing.

The advantage of this system, aside from the fact that it is maintenance free, is that the control module can handle much higher primary voltage than the mechanical points. Voltage can even be stepped up before sending it to the coil, so the coil can create a much hotter spark, on the order of 50,000 volts instead of 20,000 volts that is common with the mechanical systems. These systems only have a single wire from the ignition switch to the coil since a primary resistor is no longer needed.

On some vehicles, this control module was mounted inside the distributor where the points used to be mounted. On other designs, the control module was mounted outside the distributor with external wiring to connect it to the pickup coil. On many General Motors engines, the control module was inside the distributor and the coil was mounted on top of the distributor for a one piece unitized ignition system. GM called it High Energy Ignition or HEI for short.

The higher voltage that these systems provided allow the use of a much wider gap on the spark plugs for a longer, fatter spark. This larger spark also allowed a leaner mixture for better fuel economy and still insure a smooth running engine.

The early electronic systems had limited or no computing power, so timing still had to be set manually and there was still a centrifugal and vacuum advance built into the distributor.

On some of the later systems, the inside of the distributor is empty and all triggering is performed by a sensor that watches a notched wheel connected to either the crankshaft or the camshaft. These devices are called Crankshaft Position Sensor or Camshaft Position Sensor. In these systems, the job of the distributor is solely to distribute the spark to the correct cylinder through the distributor cap and rotor. The computer handles the timing and any timing advance necessary for the smooth running of the engine.

The Distributorless Ignition system
(from 1980's to today)

Newer automobiles have evolved from a mechanical system (distributor) to a completely solid state electronic system with no moving parts. These systems are completely controlled by the on-board computer. In place of the distributor, there are multiple coils that each serve one or two spark plugs. A typical 6 cylinder engine has 3 coils that are mounted together in a coil "pack". A spark plug wire comes out of each side of the individual coil and goes to the appropriate spark plug. The coil fires both spark plugs at the same time. One spark plug fires on the compression stroke igniting the fuel-air mixture to produce power, while the other spark plug fires on the exhaust stroke and does nothing. On some vehicles, there is an individual coil for each cylinder mounted directly on top of the spark plug. This design completely eliminates the high tension spark plug wires for even better reliability. Most of these systems use spark plugs that are designed to last over 100,000 miles, which cuts down on maintenance costs.

A Short Course on Brakes
by Charles Ofria

The modern automotive brake system has been refined for over 100 years and has become extremely dependable and efficient.

The typical brake system consists of disk brakes in front and either disk or drum brakes in the rear connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder. Other systems that are connected with the brake system include the parking brakes, power brake booster and the anti-lock

system.

When you step on the brake pedal, you are actually pushing against a plunger in the master cylinder, which forces hydraulic oil (brake fluid) through a series of tubes and hoses to the braking unit at each wheel. Since hydraulic fluid (or any fluid for that matter) cannot be compressed, pushing fluid through a pipe is just like pushing a steel bar through a pipe. Unlike a steel bar, however, fluid can be directed through many twists and turns on its way to its destination, arriving with the exact same motion and pressure that it started with. It is very important that the fluid is pure liquid and that there are no air bubbles in it. Air can compress, which causes a sponginess to the pedal and severely reduced braking efficiency. If air is suspected, then the system must be bled to remove the air. There are "bleeder screws" at each wheel cylinder and caliper for this purpose.

On a disk brake, the fluid from the master cylinder is forced into a caliper where it presses against a piston. The piston, in-turn, squeezes two brake pads against the disk (rotor), which is attached to the wheel, forcing it to slow down or stop.

This process is similar to a bicycle brake where two rubber pads rub against the wheel rim creating friction.

With drum brakes, fluid is forced into the wheel cylinder, which pushes the brake shoes out so that the friction linings are pressed against the drum, which is attached to the wheel, causing the wheel to stop.

In either case, the friction surfaces of the pads on a disk brake system, or the shoes on a drum brake convert the forward motion of the vehicle into heat. Heat is what causes the friction surfaces (linings) of the pads and shoes to eventually wear out and require replacement.

Let's take a closer look at each of the components in a brake system and see where other problems can occur...

Master Cylinder

The master cylinder is located in the engine compartment on the firewall, directly in front of the driver's seat. A typical master cylinder is actually two completely separate master cylinders in one housing, each handling two wheels. This way if one side fails, you will still be able to stop the car. The brake warning light on the dash will light if either side fails, alerting you to the problem. Master cylinders have become very reliable and rarely malfunction; however, the most common problem that they experience is an internal leak. This will cause the brake pedal to slowly sink to the floor when your foot applies steady pressure. Letting go of the pedal and immediately stepping on it again brings the pedal back to normal height.

Brake Fluid

Brake fluid is a special oil that has specific properties. It is designed to withstand cold temperatures without thickening as well as very high temperatures without boiling. (If the brake fluid should boil, it will cause you to have a spongy pedal and the car will be hard to stop.) Brake fluid must meet standards that are set by the Department of Transportation (DOT). The current standard is DOT-3, which has a boiling point of 460: F. But check your owners manual to see what your vehicle manufacturer recommends.

The brake fluid reservoir is on top of the master cylinder. Most cars today have a transparent reservoir so that you can see the level without opening the cover. The brake fluid level will drop slightly as the brake pads wear. This is a normal condition and no cause for concern. If the level drops noticeably over a short period of time or goes down to about two thirds full, have your brakes checked as soon as possible. Keep the reservoir covered except for the amount of time you need to fill it and never leave a can of brake fluid uncovered. Brake fluid must maintain a high boiling point. Exposure to air will cause the fluid to absorb moisture, which will lower that boiling point. NEVER PUT ANYTHING BUT APPROVED BRAKE FLUID IN YOUR BRAKES. ANYTHING ELSE CAN CAUSE SUDDEN BRAKE FAILURE! Any other type of oil or other fluid will react with the brake fluid and very quickly destroy the rubber seals in the brake system causing brake failure.

Brake Lines

The brake fluid travels from the master cylinder to the wheels through a series of steel tubes and reinforced

rubber hoses. Rubber hoses are used only in places that require flexibility, such as at the front wheels, which move up and down as well as steer. The rest of the system uses non-corrosive seamless steel tubing with special fittings at all attachment points. If a steel line requires a repair, the best procedure is to replace the complete line. If this is not practical, a line can be repaired using special splice fittings that are made for brake system repair. You must never use brass "compression" fittings or copper tubing to repair a brake system. They are dangerous and illegal.

Other Components in the Hydraulic System



Proportioning valve or Equalizer Valve These valves are mounted between the master cylinder and the rear wheels. They are designed to adjust the pressure between the front and rear brakes depending on how hard you are stopping. The shorter you stop, the more of the vehicle's weight is transferred to the front wheels, in some cases, causing the rear to lift and the front to dive. These valves are designed to direct more pressure to the front and less pressure to the rear the harder you stop. This minimizes the chance of premature lockup at the rear wheels.



Pressure Differential Valve This valve is usually mounted just below the master cylinder and is responsible for turning the brake warning light on when it detects a malfunction. It measures the pressure from the two sections of the master cylinder and compares them. Since it is mounted ahead of the proportioning or equalizer valve, the two pressures it detects should be equal. If it detects a difference, it means that there is probably a brake fluid leak somewhere in the system.



Combination Valve The Combination valve is simply a proportioning valve and a pressure differential valve that is combined into one unit.



Electronic Brake Force Distribution Newer cars use the antilock brake hardware and the onboard computer to replace these proportioning valve systems with a system called Electronic Brake force Distribution (EBD) in order to distribute the exact amount of pressure at each wheel to insure a balanced brake system.

Disk Brakes

The disk brake is the best brake we have found so far. Disk brakes are used to stop everything from cars to locomotives and jumbo jets. Disk brakes wear longer, are less affected by water, are self adjusting, self cleaning, less prone to grabbing or pulling and stop better than any other system around. The main components of a disk brake are the Brake Pads, Rotor, Caliper and Caliper Support.



Brake Pads There are two brake pads on each caliper. They are constructed of a metal "shoe" with the lining riveted or bonded to it. The pads are mounted in the caliper, one on each side of the rotor. Brake linings used to be made primarily of asbestos because of its heat absorbing properties and quiet operation; however, due to health risks, asbestos has been outlawed, so new materials are now being used. Brake pads wear out with use and must be replaced periodically. There are many types and qualities of pads available. The differences have to do with brake life (how long the new pads will last) and noise (how quiet they are when you step on the brake). Harder linings tend to last longer and stop better under heavy use but they may produce an irritating squeal when they are applied. Technicians that work on brakes usually have a favorite pad that gives a good compromise that their customers can live with.

Brake pads should be checked for wear periodically. If the lining wears down to the metal brake shoe, then you will have a "Metal-to-Metal" condition where the shoe rubs directly against the rotor causing severe damage and loss of braking efficiency. Some brake pads come with a "brake warning sensor" that will emit a squealing noise when the pads are worn to a point where they should be changed. This noise will usually be heard when your foot is off the brake and disappear when you step on the brake. If you hear this noise, have your brakes checked as soon as possible.



Rotor The disk rotor is made of iron with highly machined surfaces where the brake pads contact it. Just as the brake pads wear out over time, the rotor also undergoes some wear, usually in the form of ridges and groves where the brake pad rubs against it. This wear pattern exactly matches the wear pattern of the pads as they seat themselves to the rotor. When the pads are replaced, the rotor must be machined smooth to allow the new pads to have an even contact surface to work with. Only a small amount of material can be machined off of a rotor before it becomes unusable and must be replaced. A minimum thickness measurement is stamped on every rotor and the technician doing the brake job will measure the rotor before and after machining it to make sure it doesn't go below the legal minimum. If a rotor is cut below the minimum, it will not be able to handle the high heat that brakes normally generate. This will cause the brakes to "fade," greatly reducing their effectiveness to a point where you may not be able to stop!



Caliper & Support

There are two main types of calipers: Floating calipers and fixed calipers. There are other configurations but these are the most popular. Calipers must be rebuilt or replaced if they show signs of leaking brake fluid.

Single Piston Floating Calipers are the most popular and also least costly to manufacture and service. A floating caliper "floats" or moves in a track in its support so that it can center itself over the rotor. As you apply brake pressure, the hydraulic fluid pushes in two directions. It forces the piston against the inner pad, which in turn pushes against the rotor. It also pushes the caliper in the opposite direction against the outer pad, pressing it against the other side of the rotor. Floating calipers are also available on some vehicles with two pistons mounted on the same side. Two piston floating calipers are found on more expensive cars and can provide an improved braking "feel".

Four Piston Fixed Calipers are mounted rigidly to the support and are not allowed to move. Instead, there are two pistons on each side that press the pads against the rotor. Four piston calipers have a better feel and are more efficient, but are more expensive to produce and cost more to service. This type of caliper is usually found on more expensive luxury and high performance cars.

Drum Brakes

So if disk brakes are so great, how come we still have cars with drum brakes? The reason is cost. While all vehicles produced for many years have disk brakes on the front, drum brakes are cheaper to produce for the rear wheels. The main reason is the parking brake system. On drum brakes, adding a parking brake is the simple addition of a lever, while on disk brakes, we need a complete mechanism, in some cases, a complete mechanical drum brake assembly inside the disk brake rotor! Parking brakes must be a separate system that does not use hydraulics. It must be totally mechanical, but more on parking brakes later.

Drum brakes consist of a backing plate, brake shoes, brake drum, wheel cylinder, return springs and an automatic or self-adjusting system. When you apply the brakes, brake fluid is forced under pressure into the wheel cylinder, which in turn pushes the brake shoes into contact with the machined surface on the inside of the drum. When the pressure is released, return springs pull the shoes back to their rest position. As the brake linings wear, the shoes must travel a greater distance to reach the drum. When the distance reaches a certain point, a selfadjusting mechanism automatically reacts by adjusting the rest position of the shoes so that they are closer to the drum.



Brake Shoes Like the disk pads, brake shoes consist of a steel shoe with the friction material or lining riveted or bonded to it. Also like disk pads, the linings eventually wear out and must be replaced. If the linings are allowed to wear through to the bare metal shoe, they will cause severe damage to the brake drum.



Backing Plate The backing plate is what holds everything together. It attaches to the axle and forms a solid surface for the wheel cylinder, brake shoes and assorted hardware. It rarely causes any problems.



Brake Drum Brake drums are made of iron and have a machined surface on the inside where the shoes make contact. Just as with disk rotors, brake drums will show signs of wear as the brake linings seat themselves against the machined surface of the drum. When new shoes are installed, the brake drum should be machined smooth. Brake drums have a maximum diameter specification that is stamped on the outside of the drum. When a drum is machined, it must never exceed that measurement. If the surface cannot be machined within that limit, the drum must be replaced.



Wheel Cylinder The wheel cylinder consists of a cylinder that has two pistons, one on each side. Each piston has a rubber seal and a shaft that connects the piston with a brake shoe. When brake pressure is applied, the pistons are forced out pushing the shoes into contact with the drum. Wheel cylinders must be rebuilt or replaced if they show signs of leaking.



Return Springs Return springs pull the brake shoes back to their rest position after the pressure is released from the wheel cylinder. If the springs are weak and do not return the shoes all the way, it will cause premature lining wear because the linings will remain in contact with the drum. A good technician will examine the springs during a brake job and recommend their replacement if they show signs of fatigue. On certain vehicles, the technician may recommend replacing them even if they look good as inexpensive insurance.



Self Adjusting System The parts of a self adjusting system should be clean and move freely to insure that the brakes maintain their adjustment over the life of the linings. If the self adjusters stop working, you will notice that you will have to step down further and further on the brake pedal before you feel the brakes begin to engage. Disk brakes are self adjusting by nature and do not require any type of mechanism. When a technician performs a brake job, aside from checking the return springs, he will also clean and lubricate the self adjusting parts where necessary.

Parking Brakes

The parking brake (a.k.a. emergency brake) system controls the rear brakes through a series of steel cables that are connected to either a hand lever or a foot pedal. The idea is that the system is fully mechanical and completely bypasses the hydraulic system so that the vehicle can be brought to a stop even if there is a total brake failure. On drum brakes, the cable pulls on a lever mounted in the rear brake and is directly connected to the brake shoes. this has the effect of bypassing the wheel cylinder and controlling the brakes directly. Disk brakes on the rear wheels add additional complication for parking brake systems. There are two main designs for adding a mechanical parking brake to rear disk brakes. The first type uses the existing rear wheel caliper and adds a lever attached to a mechanical corkscrew device inside the caliper piston. When the parking brake cable pulls on the lever, this corkscrew device pushes the piston against the pads, thereby bypassing the hydraulic system, to stop the vehicle. This type of system is primarily used with single piston floating calipers, if the caliper is of the four piston fixed type, then that type of system can't be used. The other system uses a complete mechanical drum brake unit mounted inside the rear rotor. The brake shoes on this system are connected to a lever that is pulled by the

parking brake cable to activate the brakes. The brake "drum" is actually the inside part of the rear brake rotor.

On cars with automatic transmissions, the parking brake is rarely used. This can cause a couple of problems. The biggest problem is that the brake cables tend to get corroded and eventually seize up causing the parking brake to become inoperative. By using the parking brake from time to time, the cables stay clean and functional. Another problem comes from the fact that the self adjusting mechanism on certain brake systems uses the parking brake actuation to adjust the brakes. If the parking brake is never used, then the brakes never get adjusted.

Power Brake Booster

The power brake booster is mounted on the firewall directly behind the master cylinder and, along with the master cylinder, is directly connected with the brake pedal. Its purpose is to amplify the available foot pressure applied to the brake pedal so that the amount of foot pressure required to stop even the largest vehicle is minimal. Power for the booster comes from engine vacuum. The automobile engine produces vacuum as a by-product of normal operation and is freely available for use in powering accessories such as the power brake booster. Vacuum enters the booster through a check valve on the booster. The check valve is connected to the engine with a rubber hose and acts as a oneway valve that allows vacuum to enter the booster but does not let it escape. The booster is an empty shell that is divided into two chambers by a rubber diaphragm. There is a valve in the diaphragm that remains open while your foot is off the brake pedal so that vacuum is allowed to fill both chambers. When you step on the brake pedal, the valve in the diaphragm closes, separating the two chambers and another valve opens to allow air in the chamber on the brake pedal side. This is what provides the power assist. Power boosters are very reliable and cause few problems of their own, however, other things can contribute to a loss of power assist. In order to have power assist, the engine must be running. If the engine stalls or shuts off while you are driving, you will have a small reserve of power assist for two or three pedal applications but, after that, the brakes will be extremely hard to apply and you must put as much pressure as you can to bring the vehicle to a stop.

Anti-Lock Brakes (ABS)

The most efficient braking pressure takes place just before each wheel locks up. When you slam on the brakes in a panic stop and the wheels lock up, causing a screeching sound and leaving strips of rubber on the pavement, you do not stop the vehicle nearly as short as it is capable of stopping. Also, while the wheels are locked up, you loose all steering control so that, if you have an opportunity to steer around the obstacle, you will not be able to do so. Another problem occurs during an extended skid is that you will burn a patch of rubber off the tire, which causes a "flat spot" on the tread that will produce an annoying thumping sound as you drive.

Anti-lock brake systems solve this lockup problem by rapidly pumping the brakes whenever the system detects a

wheel that is locked up. In most cases, only the wheel that is locked will be pumped, while full braking pressure stays available to the other wheels. This effect allows you to stop in the shortest amount of time while maintaining full steering control even if one or more wheels are on ice. The system uses a computer to monitor the speed of each wheel. When it detects that one or more wheels have stopped or are turning much slower than the remaining wheels, the computer sends a signal to momentarily remove and reapply or pulse the pressure to the affected wheels to allow them to continue turning. This "pumping" of the brakes occurs at ten or more times a second, far faster then a human can pump the brakes manually. If you step on the brakes hard enough to engage the anti-lock system, you may feel a strong vibration in the brake pedal. This is a normal condition and indicates that the system is working, however, it can be disconcerting to some people who don't expect it. If your vehicle has anti-lock brakes, read your owner's manual to find out more about it.

The system consists of an electronic control unit, a hydraulic actuator, and wheel speed sensors at each wheel. If the control unit detects a malfunction in the system, it will illuminate an ABS warning light on the dash to let you know that there is a problem. If there is a problem, the anti-lock system will not function but the brakes will otherwise function normally.

Copyright ) 2000-2005, SmartTrac Computer Systems, Inc.

A Short Course on Wheel Alignment
by Charles Ofria

In its most basic form, a wheel alignment consists of adjusting the angles of the wheels so that they are perpendicular to the ground and parallel to each other. The purpose of these adjustments is maximum tire life and a vehicle that tracks straight and true when driving along a straight and level road.

This article begins with information that any motorist should know; however, if you are interested in learning more about this topic, click on the underlined words for more detailed explanations of each term. We will cover various levels of detail with the deepest levels containing information that even a wheel alignment technician will find informative.

Photo courtesy Hunter Engineering Co.

Wheel Alignment is often confused with Wheel Balancing. The two really have nothing to do with each other except for the fact that they affect ride and handling. If a wheel is out of balance, it will cause a vibration at highway speeds that can be felt in the steering wheel and/or the seat. If the alignment is out, it can cause excessive tire wear and steering or tracking problems. For more information on Wheel Balancing, Click Here.

(Article Continues below)

If you know anything about wheel alignment, you've probably heard the terms

Camber, Caster and Toe-

in.

Camber
Camber is the angle of the wheel, measured in degrees, when viewed from the front of the vehicle. If the top of the wheel is leaning out from the center of the car, then the camber is positive ,if it's leaning in, then the camber is negative. If the camber is out of adjustment, it will cause tire wear on one side of the tire's tread. If the camber is too far negative, for instance, then the tire will wear on the inside of the tread.

Camber wear pattern

If the camber is different from side to side it can cause a pulling problem. The vehicle will pull to the side with the more positive camber. On many front-wheel-drive vehicles, camber is not adjustable. If the camber is out on these cars, it indicates that something is worn or bent, possibly from an accident and must be repaired or replaced.

Caster

When you turn the steering wheel, the front wheels respond by turning on a pivot attached to the suspension system. Caster is the angle of this steering pivot, measured in degrees, when viewed from the side of the vehicle. If the top of the pivot is leaning toward the rear of the car, then the caster is positive, if it is leaning toward

the front, it is negative. If the caster is out of adjustment, it can cause problems in straight line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump. Caster has little affect on tire wear.

The best way to visualize caster is to picture a shopping cart caster. The pivot of this type of caster, while not at an angle, intersects the ground ahead of the wheel contact patch. When the wheel is behind the pivot at the point where it contacts the ground, it is in positive caster. Picture yourself trying to push the cart and keep the wheel ahead of the pivot. The wheel will continually try to turn from straight ahead. That is what happens when a car has the caster set too far negative. Like camber, on many front-wheel-drive vehicles, caster is not adjustable. If the caster is out on these cars, it indicates that something is worn or bent, possibly from an accident, and must be repaired or replaced.

Toe-in
The toe measurement is the difference in the distance between the front of the tires and the back of the tires. It is measured in fractions of an inch in the US and is usually set close to zero which means that the wheels are parallel with each other. Toe-in means that the fronts of the tires are closer to each other than the rears. Toe-out is just the opposite. An incorrect toe-in will cause rapid tire wear to both tires equally. This type of tire wear is called a saw-tooth wear pattern as

shown in this illustration.

If the sharp edges of the tread sections are pointing to the center of the car, then there is too much toe-in. If they are pointed to the outside of the car then there is too much toe-out. Toe is always adjustable on the front wheels and on some cars, is also adjustable for the rear wheels.

Four-Wheel Alignments
There are two main types of 4-wheel alignments. In each case, the technician will place an instrument on all four wheels. In the first type the rear toe and tracking is checked, but all adjustments are made at the front wheels. This is done on vehicles that do not have adjustments on the rear. The second type is a full 4-wheel alignment

where the adjustments are first made to true up the rear alignment, then the front is adjusted. A full 4-wheel alignment will cost more than the other type because there is more work involved.

Other facts every driver should know about wheel alignments.
 
A proper wheel alignment should always start and end with a test drive.

The front end and steering linkage should be checked for wear before performing an alignment.



The tires should all be in good shape with even wear patterns. If you have a tire with excessive camber wear, for instance, and you correct the alignment problem that caused that wear, the tire will now be making only partial contact with the road. (see illustration on right)



Pulling problems are not always related to wheel alignment. Problems with tires (especially unequal air pressure), brakes and power steering can also be responsible. It is up to a good wheel alignment technician to determine the cause.

Advanced Wheel Alignment Information.
While Camber, Caster & Toe-in are the settings that are always checked when doing a wheel alignment, they are not the only settings. Below is a list of the alignment settings that are important for a wheel alignment technician to know about in order to diagnose front end problems.

To find out more about each of these measurements, click on them.

      

Camber

Caster

Toe

Steering Axis Inclination (SAI)

Included Angle

Scrub Radius

Riding Height

   

Set Back

Thrust Angle

Steering Center

Toe Out on Turns

Camber
When camber specifications are determined during the design stage, a number of factors are taken into account. The engineers account for the fact that wheel alignment specifications used by alignment technicians are for a vehicle that is not moving. On many vehicles, camber changes with different road speeds. This is because aerodynamic forces cause a change in riding height from the height of a vehicle at rest. Because of this, riding height should be checked and problems corrected before setting camber. Camber specs are set so that when a vehicle is at highway speed, the camber is at the optimal setting for minimum tire wear.

For many years the trend has been to set the camber from zero to slightly positive to offset vehicle loading, however the current trend is to slightly negative settings to increase vehicle stability and improve handling.

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Caster
Positive caster improves straight line tracking because the caster line (the line drawn through the steering pivot when viewed from the side) intersects the ground ahead of the contact patch of the tire. Just like a shopping cart caster, the wheel is forced behind the pivot allowing the vehicle to track in a straight line.

If this is the case, then why did most cars have negative caster specs prior to 1975 ? There are a couple of reasons for this. In those days, people were looking for cars that steered as light as a feather, and cars back then were not equipped with radial tires. Non-radial tires had a tendency to distort at highway speed so that the contact patch moved back past the centerline of the tire (Picture a cartoon car speeding along, the tires are generally drawn as egg-shaped). The contact patch generally moves behind the caster line causing, in effect, a positive caster. This is why, when you put radial tires on this type of car, the car wanders from side to side and no longer tracks straight. To correct this condition, re-adjust the caster to positive and the car should steer like a new car.

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Toe
Like camber, toe will change depending on vehicle speed. As aerodynamic forces change the riding height, the toe setting may change due to the geometry of the steering linkage in relation to the geometry of the suspension. Because of this, specifications are determined for a vehicle that is not moving based on the toe being at zero when the vehicle is at highway speed. In the early days prior to radial tires, extra toe-in was added to compensate for tire drag at highway speed.

On some older alignment machines, toe-in was measured at each wheel by referencing the opposite wheel. This method caused problems with getting the steering wheel straight the first time and necessitated corrective adjustments before the wheel was straight. Newer machines reference the vehicle's centerline by putting instruments on all four wheels. For more information on this see Steering Center and Thrust angle.

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Steering Axis Inclination (SAI)
SAI is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. This angle, when added to the camber to form the included angle (see below) causes the vehicle to lift slightly when you turn the wheel away from a straight ahead position. This action uses the weight of the vehicle to cause the steering wheel to return to the center when you let go of it after making a turn. Because of this, if the SAI is different from side to side, it will cause a pull at very slow speeds. Most alignment machines have a way to measure SAI; however it is not separately adjustable. The most likely cause for SAI being out is bent parts which must be replaced to correct the condition. SAI is also referred to as KPI (King Pin Inclination) on trucks and old cars with king pins instead of ball joints.

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Included Angle
Included angle is the angle formed between the SAI and the camber. Included angle is not directly measurable. To determine the included angle, you add the SAI to the camber. If the camber is negative, then the included angle will be less than the SAI, if the camber is positive, it will be greater. The included

angle must be the same from side to side even if the camber is different. If it is not the same, then something is bent, most likely the steering knuckle.

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Scrub Radius
Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Different wheels or tires from side to side will cause differences in scrub radius as well as a tire that is low on air. Positive scrub radius is when the tire contact patch is outside of the SAI pivot, while negative scrub radius is when the contact patch is inboard of the SAI pivot (front wheel drive vehicles usually have negative scrub radius).

If the brake on one front wheel is not working, with positive scrub radius, stepping on the brake will cause the steering wheel to try to rip out of your hand. Negative scrub radius will minimize that effect.

Scrub radius is designed at the factory and is not adjustable. If you have a vehicle that is pulling even though the alignment is correct, look for something that will affect scrub radius.

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Riding Height
Riding height is measured, usually in inches, from the rocker panel to the ground. Good wheel alignment charts provide specs, but the main thing is that the measurements should be within one inch from side to side and front to rear. Riding height is not adjustable except on vehicles with torsion bar type springs. The best way to fix this problem is to replace the springs

(Note: springs should only be replaced in matched pairs). Changes in riding height will affect camber and toe so if springs are replaced or torsion bars are adjusted, then the wheel alignment must be checked to avoid the possibility of tire wear. It is important to note that the only symptom of weak coil springs is a sag in the riding height. If the riding height is good, then the springs are good.

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Set Back
Set back is when one front wheel is set further back than the other wheel. With alignment equipment that measures toe by using only the front instruments, any setback will cause an uncentered steering wheel. Any good 4-wheel aligner will reference the rear wheels when setting toe in order to eliminate this problem.

Some good alignment equipment will measure set back and give you a reading in inches or millimeters. A set back of less than 1/4 inch is considered normal tolerance by some manufacturers. More than that and there is a good chance that something is bent.

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Thrust Angle
Thrust angle is the direction that the rear wheels are pointing in relation to the center line of the vehicle. If the thrust angle is not zero, then the vehicle will "dog track" and the steering wheel will not be centered. The best solution is to first adjust the rear toe to the center line and then adjust the front toe. This is normally done during a 4-wheel alignment as long as the rear toe is adjustable. If the rear is not adjustable, then the front toe must be set to compensate for the thrust angle, allowing the steering to be centered.

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Steering Center
Steering center is simply the fact that the steering wheel is centered when the vehicle is traveling down a straight and level road. A crooked steering wheel is usually the most common complaint that a customer has after a wheel alignment is performed. Assuming that the steering wheel stays in the same position when you let go of the wheel (in other words, the car is not pulling), then steering center is controlled by the front and rear toe settings. When setting steering center, the rear toe should be set first bringing the Thrust Angle as close to the vehicle centerline as possible. Then the steering wheel is locked in a straight ahead position while the front toe is set. Before locking the steering wheel, the engine should be started and the wheel should be turned right and left a couple of times to take any stress off the power steering valve. After setting the toe, the engine should be started again to be sure that the steering valve wasn't loaded again due to the tie rod adjustments. Of course, you should always road test the vehicle after every alignment as a quality control check.

Another problem with steering center has to do with the type of roads that are driven on. Most roads are crowned to allow for water drainage, and unless you drive in England, Japan or another country where they drive on the wrong (sorry) left side of the road, you usually drive on the right side of the crown. This may cause the vehicle to drift to the right so that the steering wheel will appear to be off-center to the left on a straight road. The best way to compensate for this is as follows:



If there is a difference in caster, it should be that the left wheel is more negative than the right wheel, but not more than 1/2 degree. Check the specs for any specific recommendations on side-to-side differences.



If there is a difference in camber, then the left wheel should be more positive than the right wheel. Check the specs to see what the allowable difference is.

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Toe Out on Turns
When you steer a car through a turn, the outside front wheel has to navigate a wider arc then the inside wheel. For this reason, the inside front wheel must steer at a sharper angle than the outside wheel.

Toe-out on turns is measured by the turning angle gauges (turn plates) that are a part of every wheel alignment machine. The readings are either directly on the turn plate or they are measured electronically and displayed on the screen. Wheel alignment specifications will usually provide the measurements for toe-out on turns. They will give an angle for the inside wheel and the outside wheel such as 20: for the inside wheel and 18: for the outside wheel. Make sure that the readings are at zero on each side when the wheels are straight ahead, then turn the steering wheel so that the inside wheel is at the inside spec. then check the outside wheel.

The toe-out angles are accomplished by the angle of the steering arm. This arm allows the inside wheel to turn sharper than the outside wheel. The steering arm is either part of the steering knuckle or part of the ball joint and is not adjustable. If there is a problem with the toe-out, it is due to a bent steering arm that must be replaced.

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Copyright ) 1984-2007, SmartTrac

Introduction
For thousands of years, propulsion for personal transportation was provided by a beast of burden hitched to a wooden wagon or sled. Then, about a hundred years ago, someone got the bright idea to attach a new-fangled contraption called the "internal combustion engine" to that wagon, creating "the horseless carriage." And so the automotive industry was born and with it came ongoing improvements to the piston-driven internal combustion engine until it evolved into the incredible, fuel-efficient, power plant that propels our modern vehicles. Yet, refinements aside, the governing principles behind the basic functioning of the typical modern automotive engine are identical to those of the Model-T Ford.

It is not that we haven't tried to come up with alternatives to the piston engine. We have developed numerous systems. In fact, electric cars have been around for as long as the piston engine. We have also tried steam, gas turbines, rotary engines and solar powered cars. But none of these could rival the power and efficiency of the internal combustion piston engine, fed by fossil fuel and connected to a transmission that turns the drive wheels through a series of shafts and gears.

Unfortunately, nagging problems like fuel shortages and air pollution necessitate a renewed search for alternative power sources for our personal transportation needs. While engineers have been ingenious in proposing new ideas for propulsion systems that are far more efficient than anything that we have today, the problem is that most of these technologies rely on fuels other than gasoline and there is no system in place to deliver these fuels to us at anything close to the price that we now pay for gas.

Can we build an infrastructure to deliver a better fuel, whatever it may be? Probably. But who will build it? The oil companies say that they will build such a system as soon as there are enough cars to make it profitable, but who will buy one of these cars before the required fuel is available? It's the classic catch-22.

Government intervened in California by requiring a percentage of cars sold to be zero-emission vehicles by a specified date. The only currently available technology that could meet the zero emissions goal was an electric car, so manufacturers dutifully designed and built electric cars for sale in California and even subsidized the cost of these vehicles to make them attractive for consumers. The program was a dismal failure. Few people wanted to bear the inconvenience of a car with a range of less than 100 miles, after which they had to plug it into an outlet for hours of recharging. The answer looked like it might have to to come from some kind of liquid or gaseous fuel that could be dumped into a vehicle in minutes and provide a range of a few hundred miles before the process had to be repeated. So we're back to the catch-22.

There is a partial answer to this conundrum available today in the form of an innovative technology that uses existing fuel supplies more efficiently. This promising technology combines a gasoline engine with an electric motor to stretch a gallon of gas further than ever before possible. The vehicles that use this technology are called Hybrids because they use a combination of a very efficient gasoline engine and a hi-tech electric motor to propel the vehicle.

The Concept:
How the hybrid system works in simple terms
Despite the fact that they use electric motors that draw their power from a battery, hybrid vehicles do not have to be plugged in to recharge... Ever. The battery is recharged from two sources, and herein lies this system's advantage. The first source is from a generator powered by the internal combustion engine. The second source is through reclaiming the energy that is normally wasted slowing and stopping the vehicle. Let's look at the second method first because that is the most intriguing.

When you step on the brakes to slow a vehicle, you are counteracting the energy of a one or two ton projectile that wants to keep going because of inertia. In order to slow the vehicle, you must convert the energy of inertia into a different form: heat. The brakes heat up, absorbing the energy of the speeding vehicle, and the air that is directed around them then dissipates the heat, carrying it into the surroundings.

Many of us complain about how much it costs to heat a house, but here we are throwing all of our braking energy to the wind. What if we could capture some of that energy and use it later on to propel the vehicle? Well, that is

exactly what a hybrid vehicle does. It uses a property that is inherent in all electric motors: the fact that electric motors and generators are exactly the same. If you send electricity through wires into a motor, it will cause the shaft of the motor to turn, but if you find another way to turn the shaft of an electric motor, it will generate electricity back through those wires.

The more work that a motor has to perform, the more electricity it requires. In the same way, the more electrical power you demand of a generator, the harder it is to turn the shaft. So, if we set the system up so that when you first step on the brakes, it connects this motor/generator to the battery in order to charge it, the effect will be to slow the vehicle down and, voila, we have free energy that we just stored in the battery to be used later to propel the car.

On the other side of the equation, the gasoline engine can be smaller because, when it needs extra power, the electric motor is there to assist in the acceleration using the free energy in the battery that was captured the last time that the brakes were applied. Because the engine doesn't have to be as powerful, it can be more compact and deliver much better gas mileage.

The Cars:

What it's like to drive them

As of this writing, there are two, very affordable vehicles that you can buy that use hybrid technology, the Toyota Prius and the Honda Insight, with several more on the way.

The Toyota Prius, which is a 4-door, 5-passenger sedan, gets an EPA rating of 52 mpg city and 45 mpg highway while the Honda Insight, a small 2-passenger coupe gets 61 mpg city and 68 mpg highway. In the spring of 2002, you will also see a new Honda Civic hybrid that will match the 4-door 5-passenger layout of the Prius. The powertrain layout for the new Civic will be similar to the Insight. Ford will join the fray in 2003 with a hybrid version of the Escape SUV.

These cars are also environmentally friendly. Both the Prius and the Insight with the CVT (Automatic) transmission have earned an SULEV emissions rating. This means that if you were able to collect all the pollution that was emitted from one of these cars over 100,000 miles, you would just about fill a tea cup.

The Prius: Three
components make up the powertrain of the Prius, a 4 cylinder high efficiency gasoline engine, a generator and an electric motor. These components are tied together with a single planetary gear set.

There is no transmission beyond that simple gear arrangement.

To start the Prius, you turn the ignition switch to the start position, just like a normal car, but you don't hear anything. Did the car start? The indicators on the graphical display panel say that the car is running, but there is silence. Ok, on a leap of faith you put the Selector Lever in Drive and step on the accelerator pedal and, sure enough, the car takes off silently as though a large invisible hand is pushing you from behind.. As you reach about 15 mph, you notice that the gasoline engine is running though you did not hear it start.

During normal cruising above 15 mph, the gasoline engine is doing most of the work while the generator tops off the charge in the battery. Whenever you release the throttle or step on the brake, the electric motor doubles as a generator and charges the battery through regenerative braking. If more power is needed for accelerating or climbing a hill, the electric motor immediately kicks in to assist the gasoline engine using the energy that is stored in the battery. As you slow down and come to a stop, you realize that the gasoline engine is no longer running and the car is dead quiet, an eerie feeling that would have you breaking out into a cold sweat in an ordinary car.

Another thing that you notice as you accelerate is that this car does not shift. The planetary gear set acts as an infinitely variable transmission that gradually transitions from low gear to high gear in a smooth steady flow. The effect is that, while the car picks up speed, the engine seems to stay at its most efficient rpm.

Backing up is handled completely by the electric motor which serves to simplify the system and eliminate the need for a reverse gear.

The Prius rides and handles like a typical Toyota Corolla, which is to say, competently. The exterior is about the size of a Corolla as well. Interior space, however, is more like that of a Camry with plenty of room for 5 adults to ride in comfort. There is also a reasonably sized trunk, despite the fact that there is a pretty large battery pack hidden back there.

The Toyota Prius is an environmentally friendly family sedan, that is quite pleasant to drive and easy to live with. Acceleration is a bit leisurely for some of the more aggressive drivers that I know, but it is competent and will handle most traffic situations without a problem.

The brake feel takes a bit of getting used to. The car stops well, but the brake pedal feel is unusual. On a normal car, the harder that you press on the brake pedal, the stronger the stopping action, but on the Prius, a light

pressure on the brake will start with a light braking action that increases in severity even though pedal pressure hasn't changed. I'm not saying that this a safety issue at all, more of an idiosyncrasy. You will adapt to it after a while and learn to compensate until you barely notice it.

Overall, this is a nice family sedan that will make you feel good about yourself.

Click here for more photos of the Toyota Prius

The Insight:
The Honda Insight is a small two seat commuter car that gets great gas mileage and is a blast to drive and be seen in. It weighs in at a featherweight 1,887 pounds due to a lightweight aluminum body and frame that is 47-percent lighter than an equivalent steel body. Powering the Insight is a 1.0 liter, 3-cylinder VTEC engine coupled to an ultra-thin electric motor that is mounted between the engine and the transmission. The electric motor provides additional power to help the engine when it's needed during acceleration. When slowing down, the motor does double duty as a generator to recharge the battery pack. This "regenerative braking" captures energy that is normally lost through the brakes and stores it in the battery for later use to help propel the car.

Unlike the Prius, the Insight has a transmission, either a 5-speed manual or, for 2002, a new CVT automatic, and drives like a normal economy car. The engine is always running when the vehicle is moving, but will sometimes shut itself off when you stop in order to conserve fuel. As soon as you depress the clutch, the engine instantly restarts. The single electric motor is used as an assist to the 3 cylinder gasoline engine, which is the primary source of power. The electric motor becomes a generator when the computer calls upon it to charge the battery.

This system is elegant in its simplicity and certainly delivers the goods with an EPA rating of 61 mpg city and 68 mpg highway for the standard transmission model. These figures earn the Insight top billing as the most fuel efficient car sold in America. The CVT Equipped Insight comes in at a respectable 57 mpg city and 56 mpg highway.

During my week-long test drive of the stick-shift model, I rarely drove it like an economy car in my quest to find its performance potential. I was surprised by the better than 50 mpg average that this car delivered despite all the flogging,

Despite the great gas mileage, this car has good acceleration and is as much fun to drive on winding country roads as it is to dart around in city traffic.

There is only room in this car for two people and their bare essentials since there is very little storage space. As is typical for Honda, the handling and steering feel are excellent. The ride is another story, however. You will feel all the bumps and irregularities of the road surface as you drive this featherweight. Part of the reason for the choppy ride is the small, high-pressure tires that are tailored for the lowest rolling resistance possible.

If you are looking for a commuter car that won't break the bank, look no further. This is your puppy. If you like Honda but need a car that has more room, a new Civic Hybrid is just around the corner. The Honda Civic Hybrid has a new 1.3-liter i-DSI 4-cylinder engine and more advanced version of the Integrated Motor Assist (IMA) system that powers the Insight. Gas mileage is expected to be around 50 MPG for both city and highway driving and there will be room for 5.

Click here for more photos of the Honda Insight

The Nuts & Bolts: How the hardware works in technical detail
The technology that allows these two cars to get this kind of efficiency is impressive. The Toyota Prius: The components that are used to perform this magic on the Toyota Prius include: a 4 cylinder high efficiency gasoline engine and two combination generator/motors. One is mounted to the gasoline engine where the flywheel normally sits. Toyota calls this one a generator although it also serves as a starter motor. The other motor is connected to the drive wheels and is used to move the car at low speeds and assist the engine when more power is required. This motor does double duty as a generator whenever the car is coasting or slowing down. All three components (gasoline engine and 2 motor/generators) are connected through a planetary gear set. There is also a 274 volt nickel-metal hydride battery that is mounted between the back seat and the trunk.

As you can see from the picture, the combination gasoline engine, generator and electric motor forms a very compact unit that drives the front wheels.

As I mentioned before, the generator that is mounted to the back of the engine does double duty as a starter motor. To start the engine, the VVTi system increases valve overlap to reduce compression. The generator/motor then spins the engine up to about 1000 rpm. As soon as the engine is spinning up to speed, compression is brought back on line along with spark and fuel and the engine is running. No typical starter noise, no bucking, no lurching, just a smooth, almost unnoticed transition of power from electric drive to gasoline engine power.

The diagram below shows how the three components are connected through the planetary gear (power split device). The engine is connected to the planetary carrier, the generator is connected to the sun gear and the output shaft and motor are both connected to the ring gear.

If there is no load on the generator, then the engine will simply spin the generator through the planetary gears and not be able to move the car. This is what happens when the selector is in Neutral or Park. If a load is placed on the generator, either to charge the battery or to directly power the electric motor, then a portion of the engine's power will be directed through the planetary gear to the drive wheels to move the vehicle. By regulating the load on the generator, the engine RPM can be held constant while accelerating the car, thereby acting like an infinitely variable transmission. Pretty ingenious, isn't it?

By adding that second motor/generator and a single planetary gearset, Toyota was able to completely eliminate the transmission and still have the effect of a continuously variable transmission. But what about reverse gear? Simple. Backing up is handled entirely by the electric motor.

The following diagrams show the power system for the Toyota Prius

The Honda Insight powertrain is fairly straight forward front-wheel drive arrangement, consisting of a small three cylinder high-efficiency engine that is coupled to an ultra-thin electric motor mounted between the engine and either a conventional 5-

speed standard shift transmission or a new Continuously Variable Automatic Transmission (CVT). The battery is a 144 volt Nickel Metal Hydride (Ni-MH) unit that contains 120 cells of 1.2 volts each

The Insight has an all-aluminum body structure that is about half the weight of an equivalent steel body. The total weight of the Insight is a remarkable 1,856 pounds

Fuel cells and the future
Hybrid technology is an interim solution that can lessen, but not eradicate, our dependence on fossil fuel. There is another new technology called "Fuel Cells" that should be available by the end of the decade that will eliminate our dependence on non-renewable resources.

Fuel cells convert hydrogen and oxygen to electricity without going through a combustion process; thereby virtually eliminating emissions. They also operate at much higher efficiencies than internal combustion engines, producing double the amount of energy.

Most of the world's auto manufacturers have a fuel cell project in progress and virtually all of them agree that fuel cells are the propulsion system of the future.

Honda is saying that by 2010, you should expect mid-sized sedans with all the trimmings and power that we enjoy today, fueled by hydrogen that you can produce yourself in your garage using a Home Energy Station connected to your natural gas supply line. Not only will this Home Energy Station produce Hydrogen for your fuel-cell car, it will also help to heat your home.

Watch for our in-depth article on fuel cells, coming soon.

Understanding your dashboard gauges
by Charles Ofria
The minimum number of gauges on a passenger car dashboard are the speedometer and the fuel gauge. The most common additional gauge is the temperature gauge followed by the tachometer, voltmeter and oil pressure gauge. If your car does not have a temperature gauge, oil pressure gauge or charging system gauge, then you will have a warning light for these functions.

The most common configuration in today's family car is: Speedometer, Tachometer, Fuel & Temperature.

Typical instrument panel (this one is from a 2004 Ford Taurus)

Note: To find out more about the gauges on your car, the best source of information is your owner's manual.



Speedometer

In the past, the most used of the gauges. The speedometer was usually driven by a cable that spins inside a flexible tube. The cable is connected on one side to the speedometer, and on the other side to the speedometer gear inside the transmission. Today, just about all vehicles have eliminated the cable and use an electronic sensor to measure wheel speed and send the signal to an electronically driven speedometer.

The accuracy of the speedometer can be affected by the size of the tires. If the tires are larger in diameter than original equipment, the speedometer will read that you are going slower then you actually are. On older vehicles, another cause for inaccurate speed readings was an improper speedometer gear inside the transmission. This can sometimes happen after a replacement transmission has been

installed. Most good transmission shops are aware of this and will make sure that the correct speedometer gear is in the new transmission.

On vehicles with electronic speedometers, the computer has settings to for speedometer calibration when necessary, to allow a technician to adjust for different sized tires. These calibrations usually require specialized equipment like diagnostic scanners to do these types of adjustments.



Fuel Gauge

Deliberately designed to be inaccurate! After you fill up the tank, the gauge will stay on full for a long time, then slowly drop until it reads 3/4 full. After that, it moves progressively faster until the last quarter of a tank seems to go very quickly. This is a bit of psychological slight-of-hand to give the impression that the car gets better gas mileage then it does, it seems to reduce the number of complaints from new car buyers during the first few weeks after they bought the car. The fuel gauge shown here is probably more accurate than most. Notice the difference between 3/4 to full and empty to 1/4. When the needle drops below E, there is usually 1 or 2 gallons left in reserve. To find out for sure, pull out your owners manual and find out how many gallons of gas your tank holds, then the next time you fill up an empty tank, check how many gallons it took to fill it. The difference is your reserve. Note: It is not a good idea to let your tank drop below 1/4. This is because your fuel pump is submerged in fuel at the bottom of the tank. The liquid fuel helps to keep the fuel pump cool. If the fuel level goes too low and uncovers the pump, the pump will run hotter than normal. If you do this often enough, it can shorten the life of the fuel pump and eventually cause it to fail.



Temperature Gauge or warning lamp
This gauge measures the temperature of the engine coolant in degrees. When you first start the car, the gauge will read cold. If you turn the heater on when the engine is cold, it will blow cold air. When the gauge starts moving away from cold, you can then turn the heater on and get warm air. Most temperature gauges do not show degrees like the one pictured here. Instead they will read cold, hot, and have a normal range as pictured in the dash panel at the top of this page.

It is very important to monitor the temperature gauge to be sure that your engine is not overheating. If you notice that the gauge is reading much hotter than it usually is and the outside temperature is not unusually hot, have the cooling system checked as soon as possible. Note: If the temperature gauge moves all the way to hot, or if the temperature warning light comes on, the engine is overheating!

Safely pull off the road and turn the engine off and let it cool. An overheating engine can quickly cause serious engine damage!



Tachometer

The tachometer measures how fast the engine is turning in RPM (Revolutions Per Minute). This information is useful if your car has a standard shift transmission and you want to shift at the optimum RPM for best fuel economy or best acceleration. One of the least used gauges on a car with an automatic transmission. You should never race your engine so fast that the tach moves into the red zone as this can cause engine damage. Some engines are protected by the engine computer from going into the red zone. Usually, the tachometer shows single digit markings like 1, 2, 3 etc. Somewhere, you will also see an indicator that says RPM x 1000. This means that you multiply the reading by 1000 to get the actual RPM, so if the needle is pointing to 2, the engine is running at 2000 RPM.



Oil Pressure Gauge or warning lamp

Measures engine oil pressure in pounds per square inch. Oil pressure is just as important to an engine as blood pressure is to a person. If you run an engine with no oil pressure even for less then a minute, you can easily destroy it. Most cars have an oil lamp that lights when oil pressure is dangerously low. If it comes on while you're driving, stop the vehicle as soon as is safely possible and shut off the engine. Then, check the oil level and add oil as necessary.



Charging system gauge or warning lamp

The charging system is what provides the electrical current for your vehicle. Without a charging system, your battery will soon be depleted and your vehicle will shut down. The charging system gauge or warning lamp monitors the health of this system so that you have a warning of a problem before you get stuck. When a charging problem is indicated, you can still drive a short distance to find help unlike an oil pressure or coolant temperature problem which can cause serious engine damage if you continue to drive. The worst that can happen is that you get stuck in a bad location. A charging system warning lamp is a poor indicator of problems in that there are many charging problems that it will not recognize. If it does light while you are driving, it usually means the charging system is not working at all. The most common cause is a broken alternator belt. There are two types of gauges used to monitor charging systems: a voltmeter which measures system voltage and an ammeter which measures amperage going out of, or coming into the battery. Most modern cars that have gauges use a voltmeter because it is a much better indicator of charging system health. A voltmeter is usually the first tool a technician uses when checking out a charging system

A modern automobile has a 12 volt electrical system. A fully charged battery will read about 12.5 volts when the engine is not running. When the engine is running, the charging system takes over so that the voltmeter will read 14 to 14.5 volts and should stay there unless there is a heavy load on the electrical system such as

wipers, lights, heater and rear defogger all operating together while the engine is idling at which time the voltage may drop. If the voltage drops below 12.5, it means that the battery is providing some of the current. You may notice that your dash lights dim at this point. If this happens for an extended period, the battery will run down and may not have enough of a charge to start the car after shutting it off. This should never happen with a healthy charging system because as soon as you step on the gas, the charging system will recharge the battery. If the voltage is constantly below 14 volts, you should have the system checked. If the voltage ever goes above 15 volts, there is a problem with the voltage regulator. Have the system checked as soon as possible as this "overcharging" condition can cause damage to your electrical system.

If you think of electricity as water, voltage is like water pressure, whereas amperage is like the volume of water. If you increase pressure, then more water will flow through a given size pipe, but if you increase the size of the pipe, more water will flow at a lower pressure. An ammeter will read from a negative amperage when the battery is providing most of the current thereby depleting itself, to a positive amperage if most of the current is coming from the charging system. If the battery is fully charged and there is minimal electrical demand, then the ammeter should read close to zero, but should always be on the positive side of zero. It is normal for the ammeter to read a high positive amperage in order to recharge the battery after starting, but it should taper off in a few minutes. If it continues to read more than 10 or 20 amps even though the lights, wipers and other electrical devices are turned off, you may have a weak battery and should have it checked.

Automotive Air Conditioning Systems

by Chris Bede www.aircondition.com

Today, as we drive our automobiles, a great many of us, can enjoy the same comfort
levels that we are accustomed to at home and at work. With the push of a button or the slide of a lever, we make the seamless transition from heating to cooling and back again without ever wondering how this change occurs. That is, unless something goes awry.
(Article Continues below)

Since the advent of the automotive air conditioning system in the 1940's, many
things have undergone extensive change. Improvements, such as computerized automatic temperature control (which allow you to set the desired temperature and have the system adjust automatically) and improvements to overall durability, have added complexity to today's modern air conditioning system. Unfortunately, the days of "do-it-yourself" repair to these systems, is almost a thing of the past.

To add to the complications, we now have tough environmental regulations that
govern the very simplest of tasks, such as recharging the system with refrigerant R12 commonly referred to as Freon. (Freon is the trade name for the refrigerant R-12, that was manufactured by DuPont). Extensive scientific studies have proven the damaging effects of this refrigerant to our ozone layer, and its manufacture has been banned by the U.S. and many other countries that have joined together to sign the Montreal Protocol, a landmark agreement that was introduced in the 1980's to limit the production and use of chemicals known to deplete the ozone layer.

Now more than ever, your auto mechanic is at the mercy of this new environmental
legislation. Not only is he required to be certified to purchase refrigerant and repair your air conditioner, his shop must also incur the cost of purchasing expensive dedicated equipment that insures the capture of these ozone depleting chemicals, should the system be opened up for repair. Simply put, if your mechanic has to spend more to repair your vehicle - he will have to charge you more. Basic knowledge of your air conditioning system is important, as this will allow you to make a more informed decision on your repair options.

Should a major problem arise from your air conditioner, you may encounter new
terminology. Words like "retrofit" and "alternative refrigerant" are now in your

mechanics glossary. You may be given an option of "retrofitting", as opposed to merely repairing and recharging with Freon. Retrofitting involves making the necessary changes to your system, which will allow it to use the new industry accepted, "environmentally friendly" refrigerant, R-134a. This new refrigerant has a higher operating pressure, therefore, your system, dependant on age, may require larger or more robust parts to counter its inherent high pressure characteristics. This, in some cases, will add significantly to the final cost of the repair. And if not performed properly, may reduce cooling efficiency which equates to higher operating costs and reduced comfort.

Vehicles are found to have
primarily three different types of air conditioning systems. While each of the three types differ, the concept and design are very similar to one another. The most common components which make up these automotive systems are the following:
COMPRESSOR, CONDENSER, EVAPORATOR, ORIFICE TUBE, THERMAL EXPANSION VALVE , RECEIVER-DRIER, ACCUMULATOR.
Note: if your car has an Orifice tube, it will not have a Thermal Expansion Valve as these two devices serve the same purpose. Also, you will either have a Receiver-Dryer or an Accumulator, but not both.

For more information on Air Conditioning, check out The Automotive Air Conditioning Information Server

COMPRESSOR
Commonly referred to as the heart of the system, the compressor is a belt driven pump that is fastened to the engine. It is responsible for compressing and transferring refrigerant gas.

The A/C system is split into two sides, a high pressure side and a low pressure side; defined as discharge and suction. Since the compressor is basically a pump, it must have an intake side and a discharge side. The intake, or suction side, draws in refrigerant gas from the outlet of the evaporator. In some cases it does this via the accumulator. Once the refrigerant is drawn into the suction side, it is compressed and sent to the condenser, where it can then transfer the heat that is absorbed from the inside of the vehicle. Return

CONDENSER
This is the area in which heat dissipation occurs. The condenser, in many cases, will have much the same appearance as the radiator in you car as the two have very similar functions. The condenser is designed to radiate heat. Its location is usually in front of the radiator, but in some cases, due to aerodynamic improvements to the body of a vehicle, its location may differ. Condensers must have good air flow anytime the system is in operation. On rear wheel drive vehicles, this is usually accomplished by taking advantage of your existing engine's cooling fan. On front wheel drive vehicles, condenser air flow is supplemented with one or more electric cooling fan(s). As hot compressed gasses are introduced into the top of the condenser, they are cooled off. As the gas cools, it condenses and exits the bottom of the condenser as a high pressure liquid. . Return

EVAPORATOR
Located inside the vehicle, the evaporator serves as the heat absorption component. The evaporator provides several functions. Its primary duty is to remove heat from

the inside of your vehicle. A secondary benefit is dehumidification. As warmer air travels through the aluminum fins of the cooler evaporator coil, the moisture contained in the air condenses on its surface. Dust and pollen passing through stick to its wet surfaces and drain off to the outside. On humid days you may have seen this as water dripping from the bottom of your vehicle. Rest assured this is perfectly normal. The ideal temperature of the evaporator is 320 Fahrenheit or 00 Celsius. Refrigerant enters the bottom of the evaporator as a low pressure liquid. The warm air passing through the evaporator fins causes the refrigerant to boil (refrigerants have very low boiling points). As the refrigerant begins to boil, it can absorb large amounts of heat. This heat is then carried off with the refrigerant to the outside of the vehicle. Several other components work in conjunction with the evaporator. As mentioned above, the ideal temperature for an evaporator coil is 320 F. Temperature and pressure regulating devices must be used to control its temperature. While there are many variations of devices used, their main functions are the same; keeping pressure in the evaporator low and keeping the evaporator from freezing; A frozen evaporator coil will not absorb as much heat. Return

PRESSURE REGULATING DEVICES
Controlling the evaporator temperature can be accomplished by controlling refrigerant pressure and flow into the evaporator. Many variations of pressure regulators have been introduced since the 1940's. Listed below, are the most commonly found. Return

ORIFICE TUBE
The orifice tube, probably the most commonly used, can be found in most GM and Ford models. It is located in the inlet tube of the evaporator, or in the liquid line, somewhere between the outlet of the condenser and the inlet of the evaporator. This point can be found in a properly functioning system by locating the area between the

outlet of the condenser and the inlet of the evaporator that suddenly makes the change from hot to cold. You should then see small dimples placed in the line that keep the orifice tube from moving. Most of the orifice tubes in use today measure approximately three inches in length and consist of a small brass tube, surrounded by plastic, and covered with a filter screen at each end. It is not uncommon for these tubes to become clogged with small debris. While inexpensive, usually between three to five dollars, the labor to replace one involves recovering the refrigerant, opening the system up, replacing the orifice tube, evacuating and then recharging. With this in mind, it might make sense to install a larger pre filter in front of the orifice tube to minimize the risk of of this problem reoccurring. Some Ford models have a permanently affixed orifice tube in the liquid line. These can be cut out and replaced with a combination filter/orifice assembly. Return

THERMAL EXPANSION VALVE
Another common refrigerant regulator is the thermal expansion valve, or TXV. Commonly used on import and aftermarket systems. This type of valve can sense both temperature and pressure, and is very efficient at regulating refrigerant flow to the evaporator. Several variations of this valve are commonly found. Another example of a thermal expansion valve is Chrysler's "H block" type. This type of valve is usually located at the firewall, between the evaporator inlet and outlet tubes and the liquid and suction lines. These types of valves, although efficient, have some disadvantages over orifice tube systems. Like orifice tubes these valves can become clogged with debris, but also have small moving parts that may stick and malfunction due to corrosion. Return

RECEIVER-DRIER
The receiver-drier is used on the high side of systems that use a thermal expansion valve. This type of metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used. The primary function of the receiver-drier is to separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt. The receiver-drier usually has a sight glass in the top. This sight glass is often used to charge the system. Under normal operating conditions, vapor bubbles should not be visible in the sight glass. The use of the sight glass to charge the system is not recommended in R-134a systems as cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles. This type of mistake can lead to a dangerous overcharged condition. There are variations of receiver-driers and several different desiccant materials are in use. Some of the moisture

removing desiccants found within are not compatible with R-134a. The desiccant type is usually identified on a sticker that is affixed to the receiver-drier. Newer receiver-driers use desiccant type XH-7 and are compatible with both R-12 and R-134a refrigerants.

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ACCUMULATOR
Accumulators are used on systems that accommodate an orifice tube to meter refrigerants into the evaporator. It is connected directly to the evaporator outlet and stores excess liquid refrigerant. Introduction of liquid refrigerant into a compressor can do serious damage. Compressors are designed to compress gas not liquid. The chief role of the accumulator is to isolate the compressor from any damaging liquid refrigerant. Accumulators, like receiverdriers, also remove debris and moisture from a system. It is a good idea to replace the accumulator each time the system is opened up for major repair and anytime moisture and/or debris is of concern. Moisture is enemy number one for your A/C system. Moisture in a system mixes with refrigerant and forms a corrosive acid. When in doubt, it may be to your advantage to change the Accumulator or receiver in your system. While this may be a temporary discomfort for your wallet, it is of long term benefit to your air conditioning system.

The function of the fuel system is to store and supply fuel to the cylinder chamber where it can be mixed with air, vaporized, and burned to produce energy. The fuel, which can be either gasoline or diesel is stored in a fuel tank. A fuel pump draws the fuel from the tank through fuel lines and delivers it through a fuel filter to either a carburetor or fuel injector, then delivered to the cylinder chamber for combustion.

GASOLINE
Gasoline is a complex blend of carbon and hydrogen compounds. Additives are then added to improve performance. All gasoline is basically the same, but no two blends are identical. The two most important features of gasoline are volatility and resistance to knock (octane). Volatility is a measurement of how easily the fuel vaporizes. If the gasoline does not vaporize completely, it will not burn properly (liquid fuel will not burn).

If the gasoline vaporizes too easily the mixture will be too lean to burn properly. Since high temperatures increase volatility, it is desirable to have a low volatility fuel for warm temperatures and a high volatility fuel for cold weather. The blends will be different for summer and winter fuels. Vapor lock which was a persistent problem years ago, exists very rarely today. In today's cars the fuel is constantly circulating from the tank, through the system and back to the tank. The fuel does not stay still long enough to get so hot that it begins to vaporize. Resistance to knock or octane is simply the temperature the gas will burn at. Higher octane fuel requires a higher temperature to burn. As compression ratio or pressure increases so does the need for higher octane fuel. Most engines today are low compression engines therefore requiring a lower octane fuel (87). Any higher octane than

required is just wasting money. Other factors that affect the octane requirements of the engine are: air/fuel ratio, ignition timing, engine temperature, and carbon build up in the cylinder. Many automobile manufacturers have installed exhaust gas recirculation systems to reduce cylinder chamber temperature. If these systems are not working properly, the car will have a tendency to knock. Before switching to a higher octane fuel to reduce knock, make sure to have these other causes checked.

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DIESEL
Diesel fuel, like gasoline is a complex blend of carbon and hydrogen compounds. It too requires additives for maximum performance. There are two grades of diesel fuel used in automobiles today: 1-D and 2-D. Number 2 diesel fuel has a lower volatility and is blended for higher loads and steady speeds, therefore works best in large truck applications. Because number 2 diesel fuel is less volatile, it tends to create hard starting in cold weather. On the other hand number 1 diesel is more volatile, and therefore more suitable for use in an automobile, where there is constant changes in load and speed. Since diesel fuel vaporizes at a much higher temperature than gasoline, there is no need for a fuel evaporation control system as with gasoline. Diesel fuels are rated with a cetane number rather than an octane number. While a higher octane of gasoline indicates resistance to ignition, the higher cetane rating of diesel fuel indicates the ease at which the fuel will ignite. Most number 1 diesel fuels have a cetane rating of 50, while number 2 diesel fuel have a rating of 45. Diesel fuel emissions are higher in sulfur, and lower in carbon monoxide and hydrocarbons than gasoline and are subject to different emission testing standards.

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FUEL TANK
Tank location and design are always a compromise with available space. Most automobiles have a single tank located in the rear of the vehicle. Fuel tanks today have internal baffles to prevent the fuel from sloshing back and forth. If you hear noises from the rear on acceleration and deceleration the baffles could be broken. All tanks have a fuel filler pipe, a fuel outlet line to the engine and a vent system. All catalytic converter cars are equipped with a filler pipe restrictor so that leaded fuel, which is dispensed from a thicker nozzle, cannot be introduced into the fuel system. All fuel tanks must be vented. Before 1970, fuel tanks were vented to the atmosphere, emitting hydrocarbon emissions. Since 1970 all tanks are vented through a charcoal canister, into the engine to be burned before being released to the atmosphere. This is called evaporative emission control and will be discussed further

in the emission control section. Federal law requires that all 1976 and newer cars have vehicle rollover protection devices to prevent fuel spills.

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FUEL LINES
Steel lines and flexible hoses carry the fuel from the tank to the engine. When servicing or replacing the steel lines, copper or aluminum must never be used. Steel lines must be replaced with steel. When replacing flexible rubber hoses, proper hose must be used. Ordinary rubber such as used in vacuum or water hose will soften and deteriorate. Be careful to route all hoses away from the exhaust system.

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FUEL PUMPS
Two types of fuel pumps are used in automobiles; mechanical and electric. All fuel injected cars today use electric fuel pumps, while most carbureted cars use mechanical fuel pumps. Mechanical fuel pumps are diaphragm pumps, mounted on the engine and operated by an eccentric cam usually on the camshaft. A rocker arm attached to the eccentric moves up and down flexing the diaphragm and pumping the fuel to the engine. Because electric pumps do not depend on an eccentric for operation, they can be located anywhere on the vehicle. In fact they work best when located near the fuel tank.

Many cars today, locate the fuel pump inside the fuel tank. While mechanical pumps operate on pressures of 4-6 psi (pounds per square inch), electric pumps can operate on pressures of 30-40 psi. Current is supplied to the pump immediately when the key is turned. This allows for constant pressure on the system for immediate starting. Electric fuel pumps can be either low pressure or high pressure. These pumps look identical, so be careful when replacing a fuel pump that the proper one is used. Fuel pumps are rated by pressure and volume. When checking fuel pump operation, both specifications must be checked and met.

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FUEL FILTERS
The fuel filter is the key to a properly functioning fuel delivery system. This is more true with fuel injection than with carbureted cars. Fuel injectors are more susceptible to damage from dirt because of their close tolerances, but also fuel injected cars use electric fuel pumps. When the filter clogs, the electric fuel pump works so hard to push past the filter, that it burns itself up. Most cars use two filters. One inside the gas tank and one in a line to the fuel injectors or carburetor. Unless some severe and unusual condition occurs to cause a large amount of dirt to enter the gas tank, it is only necessary to replace the filter in the line.

EMISSION CONTROL SYSTEMS
by Fred Bordoff The need to control the emissions from automobiles gave rise to the computerization of the automobile. Hydrocarbons, carbon monoxide and oxides of nitrogen are created during the combustion process and are emitted into the atmosphere from the tail pipe. There are also hydrocarbons emitted as a result of vaporization of gasoline and from the crankcase of the automobile. The clean air act of 1977 set limits as to the amount of each of these pollutants that could be emitted from an automobile. The manufacturers answer was the addition of certain pollution control devices and the creation of a self adjusting engine. 1981 saw the first of these self adjusting engines. They were called feedback fuel control systems. An oxygen sensor was installed in the exhaust system and would measure the fuel content of the exhaust stream. It then would send a signal to a microprocessor, which would analyze the reading and operate a fuel mixture or air mixture device to create the proper air/fuel ratio. As computer systems progressed, they were able to adjust ignition spark timing as well as operate the other emission controls that were installed on the vehicle. The computer is also capable of monitoring and diagnosing itself. If a fault is seen, the computer will alert the vehicle operator by illuminating a malfunction indicator lamp. The computer will at the same time record the fault in it's memory, so that a technician can at a later date retrieve that fault in the form of a code which will help them determine the proper repair. Some of the more popular emission control devices installed on the automobile are: EGR VALVE, CATALYTIC CONVERTER, AIR
PUMP, PCV VALVE, CHARCOAL CANISTER.

CATALYTIC CONVERTER

Automotive emissions are controlled in three ways, one is to promote more complete combustion so that there are less by products. The second is to reintroduce excessive hydrocarbons back into the engine for combustion and the third is to provide an additional area for oxidation or combustion to occur. This additional area is called a catalytic converter. The catalytic converter looks like a muffler. It is located in the exhaust system ahead of the muffler. Inside the converter are pellets or a honeycomb made of platinum or palladium. The platinum or palladium are used as a catalyst ( a catalyst is a substance used to speed up a chemical process). As hydrocarbons or carbon monoxide in the exhaust are passed over the catalyst, it is chemically oxidized or converted to carbon dioxide and water. As the converter works to clean the exhaust, it develops heat. The dirtier the exhaust, the harder the converter works and the more heat that is developed. In some cases the converter can be seen to glow from excessive heat. If the converter works this hard to clean a dirty exhaust it will destroy itself. Also leaded fuel will put a coating on the platinum or palladium and render the converter ineffective. This is why, in the U.S.A., all fuels designed for automobile engines are now unleaded. Return

PCV VALVE
The purpose of the positive crankcase ventilation (PCV) system, is to take the vapors produced in the crankcase during the normal combustion process, and redirecting them into the air/fuel intake system to be burned during combustion. These vapors dilute the air/fuel mixture so they have to be carefully controlled and metered in order to not affect the performance of the engine. This is the job of the positive crankcase ventilation (PCV) valve. At idle, when the air/fuel mixture is very critical, just a little of the vapors are allowed in to the intake system. At high speed when the mixture is less critical and the pressures in the engine are greater, more of the vapors are allowed in to the intake system. When the valve or the system is clogged, vapors will back up into the air filter housing or at worst, the excess pressure will push past seals and create engine oil leaks. If the wrong valve is used or the system has air leaks, the engine will idle rough, or at worst, engine oil will be sucked out of the engine. Return

EGR VALVE
The purpose of the exhaust gas recirculation valve (EGR) valve is to meter a small amount of exhaust gas into the intake system, this dilutes the air/fuel mixture so as to lower the combustion chamber temperature. Excessive combustion chamber temperature creates oxides of nitrogen, which is a major pollutant. While the EGR valve is the most effective method of controlling oxides of nitrogen, in it's very design it adversely affects engine performance. The engine was not designed to run on exhaust gas. For this reason the amount of exhaust entering the intake system has to be carefully monitored and controlled. This is accomplished through a series of electrical and vacuum switches and the vehicle computer. Since EGR action reduces performance by diluting the air /fuel mixture, the system does not allow EGR action when the engine is cold or when the engine needs full power. Return

EVAPORATIVE CONTROLS
Gasoline evaporates quite easily. In the past, these evaporative emissions were vented into the atmosphere. 20% of all HC emissions from the automobile are from the gas tank. In 1970 legislation was passed, prohibiting venting of gas tank fumes into the atmosphere. An evaporative control system was developed to eliminate this source of pollution. The function of the fuel evaporative control system is to trap and store evaporative emissions from the gas tank and carburetor. A charcoal canister is used to trap the fuel vapors. The fuel vapors adhere to the charcoal, until the engine is started, and engine vacuum can be used to draw the vapors into the engine, so that they can be burned along with the fuel/air mixture. This system requires the use of a sealed gas tank filler cap. This cap is so important to the operation of the system, that a test of the cap is now being integrated into many state emission inspection programs. Pre-1970 cars released fuel vapors into the atmosphere through the use of a vented gas cap. Today with the use of sealed caps, redesigned gas tanks are used. The tank has to have the space for the vapors to collect so that they can then be vented to the charcoal canister. A purge valve is used to control the vapor flow into the engine. The purge valve is operated by engine vacuum. One common problem with this system is that the purge valve goes bad and engine vacuum draws fuel directly into the intake system. This enriches the fuel mixture and will foul the spark plugs. Most charcoal canisters have a filter that should be replaced periodically. This system should be checked when fuel mileage drops.

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AIR INJECTION
Since no internal combustion engine is 100% efficient, there will always be some unburned fuel in the exhaust. This increases hydrocarbon emissions. To eliminate this source of emissions an air injection system was created. Combustion requires fuel, oxygen and heat. Without any one of the three, combustion cannot occur. Inside the exhaust manifold there is sufficient heat to support combustion, if we introduce some oxygen than any unburned fuel will ignite. This combustion will not produce any power, but it will reduce excessive hydrocarbon emissions. Unlike in the combustion chamber, this combustion is uncontrolled, so if the fuel content of the exhaust is excessive, explosions, that sound like popping, will occur. There are times when under normal conditions, such as deceleration, when the fuel content is excessive. Under these conditions we would want to shut off the air injection system. This is accomplished through the use of a diverter valve, which instead of shutting the air pump off, diverts the air away from the exhaust manifold. Since all of this is done after the combustion process is complete, this is one emission control that has no effect on engine performance. The only maintenance that is required is a careful inspection of the air pump drive belt. Return

Automobile Battery
by Fred Bordoff
The automotive battery, also known as a lead-acid storage battery, is an electrochemical device that produces voltage and delivers current. In an automotive battery we can reverse the electrochemical action, thereby recharging the battery, which will then give us many years of service. The purpose of the battery is to supply current to the starter motor, provide current to the ignition system while cranking, to supply additional current when the demand is higher than the alternator can supply and to act as an electrical reservoir.

The automotive battery requires special handling. The electrolyte

(water) inside the battery is a mixture of sulfuric acid and water. Sulfuric acid is very corrosive; if it gets on your skin it should be flushed with water immediately; if it gets in your eyes, you should immediately flush them thoroughly with water and see a doctor right away. In this situation, time is critical. If you work with batteries often, you should have a mild solution of baking soda and water on hand and flush with that. The baking soda will neutralize the acid and minimize the damage. Remember: it is more important to flush immediately. Do not take the time to make up a solution first.

Sulfuric acid will eat through clothing, so it is advisable to wear old clothing when handling batteries. It is also advisable to wear goggles and gloves while servicing the battery. When charging, the battery will emit hydrogen gas; it is therefore extremely important to keep flames and sparks away from the battery.

Because batteries emit hydrogen gas while charging, the battery case cannot be completely sealed. Years ago there was a vent cap for each cell and we had to replenish the cells when the electrolyte evaporated. Today's batteries (maintenance free) have small vents on the side of the battery; the gases emitted have to go through baffles to escape. During this process the liquid condenses and drops back to the bottom of the battery. There's no need to replenish or add water to this type of battery.

Today's batteries are rated in cold cranking amps. This represents the current that the battery can produce for 30 seconds at 0 degrees before the battery voltage drops below 7.2 volts. An average battery today will have a CCA (Cold Cranking Amps) of 500. With the many different makes and models of cars available today, batteries will come in many different sizes, but all sizes come in many CCAs. Make sure you get a battery strong enough to operate properly in your car. The length of the warranty is not indicative of the strength of the battery.

Battery cables are large diameter, multistranded wire which carry the high current (250+ amps) necessary to operate the starter motor. Some battery cables will have a smaller wire, soldered to the terminal, which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns it indicates a high resistance in the heavy cable.

Even maintenance free batteries need periodic inspection and cleaning to insure they stay in good working order. Inspect the battery to see that it is clean and that it is held securely in its carrier. Some corrosion naturally collects around the battery. Electrolyte condensation contains corrosive sulfuric acid, which eats away the metal of battery terminals, cable ends and battery holddown parts. To clean away the corrosion, use a mixture of baking soda and water, and wash all the metal parts around the battery, being careful not to allow any of the mixture to get into the battery (batteries with top cell caps and vents). Rinse with water. Remove the battery cables from the battery (negative cable first), wire brush the inside of the cable end and the battery post. Reinstall the cables (negative end last). Coat all exposed metal parts( paint or grease can be used) so that the sulfuric acid cannot get on the metal.

The Starting System

by Fred Bordoff

The "starting system", the heart of the electrical system in your car, begins with the Battery. The key is inserted into the Ignition Switch and then turned to the start position. A small amount of current then passes through the Neutral Safety Switch to a Starter Relay or Starter Selenoid which allows high current to flow through the Battery Cables to the Starter Motor. The starter motor then cranks the engine so that the piston, moving downward, can create a suction that will draw a Fuel/Air mixture into the cylinder, where a spark created by the Ignition System will ignite this mixture. If the Compression in the engine is high enough and all this happens at the right Time, the engine will start.

Battery

The automotive battery, also known as a lead-acid storage battery, is an electrochemical device that produces voltage and delivers current. In an automotive battery we can reverse the electrochemical action, thereby recharging the battery, which will then give us many years of service. The purpose of the battery is to supply current to the starter motor, provide current to the ignition system while cranking, to supply additional current when the demand is higher than the alternator can supply and to act as an electrical reservoir.

The automotive battery requires special handling. The electrolyte (water) inside the battery is a mixture of sulfuric acid and water. Sulfuric acid is very corrosive; if it gets on your skin it should be flushed with water immediately; if it gets in your eyes it should be flushed with a mild solution of baking soda and water immediately and you should see a doctor as soon as possible. Sulfuric acid will eat through clothing, so it is advisable to wear old clothing when handling batteries. It is also advisable to wear goggles and gloves while servicing the battery. When charging, the battery will emit hydrogen gas; it is therefore extremely important to keep flames and sparks away from the battery.

Because batteries emit hydrogen gas while charging, the battery case cannot be completely sealed. Years ago there was a vent cap for each cell and we had to replenish the cells when the electrolyte evaporated. Today's

batteries (maintenance free) have small vents on the side of the battery; the gases emitted have to go through baffles to escape. During this process the liquid condenses and drops back to the bottom of the battery. There's need to replenish or add water to the battery.

Today's batteries are rated in cold cranking amps. This represents the current that the battery can produce for 30 seconds at 0 degrees before the battery voltage drops below 7.2 volts. An average battery today will have a CCA (Cold Cranking Amps) of 500. With the many different makes and models of cars available today, batteries will come in many different sizes, but all sizes come in many CCAs. Make sure you get a battery strong enough to operate properly in your car. The length of the warranty is not indicative of the strength of the battery.

Battery cables are large diameter, multistranded wire which carry the high current (250+ amps) necessary to operate the starter motor. Some battery cables will have a smaller wire, soldered to the terminal, which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns it indicates a high resistance in the heavy cable.

Even maintenance free batteries need periodic inspection and cleaning to insure they stay in good working order. Inspect the battery to see that it is clean and that it is held securely in its carrier. Some corrosion naturally collects around the battery. Electrolyte condensation contains corrosive sulfuric acid, which eats away the metal of battery terminals, cable ends and battery holddown parts. To clean away the corrosion, use a mixture of baking soda and water, and wash all the metal parts around the battery, being careful not to allow any of the mixture to get into the battery (batteries with top cell caps and vents). Rinse with water. Remove the battery cables from the battery (negative cable first), wire brush the inside of the cable end and the battery post. Reinstall the cables (negative end last). Coat all exposed metal parts( paint or grease can be used) so that the sulfuric acid cannot get on the metal.

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Ignition Switch

The ignition switch allows the driver to distribute electrical current to where it is needed. There are generally 5 key switch positions that are used:

1.

Lock- All circuits are open ( no current supplied) and the steering wheel is in the lock position. In some cars, the transmission lever cannot be moved in this position. If the steering wheel is applying pressure to the locking mechanism, the key might be hard to turn. If you do experience this type of condition, try moving the steering wheel to remove the pressure as you turn the key. 2. Off- All circuits are open, but the steering wheel can be turned and the key cannot be extracted. Run- All circuits, except the starter circuit, are closed (current is allowed to pass through). Current is supplied to all but the starter circuit.

3.

4.

Start- Power is supplied to the ignition circuit and the starter motor only. That is why the radio stops playing in the start position. This position of the ignition switch is spring loaded so that the starter is not engaged while the engine is running. This position is used momentarily, just to activate the starter.

5.

Accessory- Power is supplied to all but the ignition and starter circuit. This allows you to play the radio, work the power windows, etc. while the engine is not running.

Most ignition switches are mounted on the steering column. Some switches are actually two separate parts;

 

The lock into which you insert the key. This component also contains the mechanism to lock the steering wheel and shifter. The switch which contains the actual electrical circuits. It is usually mounted on top of the steering column just behind the dash and is connected to the lock by a linkage or rod.

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Neutral Safety Switch

This switch opens (denies current to) the starter circuit when the transmission is in any gear but Neutral or Park on automatic transmissions. This switch is normally connected to the transmission linkage or directly on the transmission. Most cars utilize this same switch to apply current to the back up lights when the transmission is put in reverse. Standard transmission cars will connect this switch to the clutch pedal so that the starter will not engage unless the clutch pedal is depressed. If you find that you have to move the shifter away from park or neutral to get the car to start, it usually means that this switch needs adjustment. If your car has an automatic parking brake release, the neutral safety switch will control that function also.

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Starter Relay

A relay is a device that allows a small amount of electrical current to control a large amount of current. An automobile starter uses a large amount of current (250+ amps) to start an engine. If we were to allow that much current to go through the ignition switch, we would not only need a very large switch, but all the wires would have to be the size of battery cables (not very practical). A starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current flow from the battery to the starter. The starter solenoid in some cases also mechanically engages the starter gear with the engine.

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Battery Cables

Battery cables are large diameter, multistranded wire which carry the high current (250+ amps) necessary to operate the starter motor. Some have a smaller wire soldered to the terminal which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns, this indicates a high resistance in the heavy cable. Care must be taken to keep the battery cable ends (terminals) clean and tight. Battery cables can be replaced with ones that are slightly larger but never smaller.

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Starter Motor

The starter motor is a powerful electric motor, with a small gear (pinion) attached to the end. When activated, the gear is meshed with a larger gear (ring), which is attached to the engine. The starter motor then spins the engine over so that the piston can draw in a fuel/ air mixture, which is then ignited to start the engine. When the engine starts to spin faster than the starter, a device called an overrunning clutch (bendix drive) automatically disengages the starter gear from the engine gear.

ON BOARD DIAGNOSTICS (OBD)
WHAT IS IT AND WHAT DOES IT MEAN TO YOU? by Fred Bordoff

OBD, or on board diagnostics, was first introduced by General Motors in 1981. The purpose of OBD was to monitor the emission control system in the car. When the computer system of the car sees a fault in the emission control system, three things are supposed to happen. First, it would set a warning light on the dashboard, to inform the driver that a problem existed. Second, to set a code in the computer. Third to record that code in the computers memory, that can be later retrieved by a technician for diagnosis and repair. This system worked so well, in 1986 California mandated that all cars sold in the state be equipped with OBD. This then became an industry standard throughout the nation, and all cars sold in the nation had some form of OBD This first version of OBD had a lot of shortcomings. First, it only covered the engine emission system. The fuel tank vapors were not monitored. The exhaust emissions were not measured. And only devices specifically installed for emission control were monitored. Second, there was no standardization throughout the industry. Each manufacturer had a different term for the warning light that was illuminated when a fault was determined. GM called it a check engine or service engine light. Chrysler called it a power loss light. Ford

called it an engine light. Most foreign cars called it a check engine light. This was not only confusing to the technician, but also to the motorist. Many motorists upon seeing the service engine light illuminated, brought their car to a repair facility and either asked for an oil change or tune-up, expecting the light to go out. Needless to say, this did not happen, and after spending unnecessary money on service work, the system then had to be diagnosed and repaired. The coding system for each manufacturer was also different making diagnosis much tougher. The clean air act of 1990 mandated that beginning with the 1996 model year, all cars sold in the U.S. be equipped with a new version of on board diagnostics This system became known as OBD II. The manufacturers beat the deadline and almost all cars were equipped with OBD II in the 1995 model year. If your car is a 1995 model or newer, chances are it is equipped with OBD II. Among the many differences between OBD and OBD II, was the standardization of the system. All dashboard warning lights now say check engine, usually with a picture of an engine with the word check across it. The coding system is now standard. There are now over 400 possible trouble codes that can be stored in the system. All causes of excessive are now monitored. If the gas cap is left loose and vapors are escaping from the gas tank, the check engine light will be illuminated and a code will be set. It is extremely important now that the engine be shut off when refueling the vehicle. Another big difference between the systems is that with OBD when a fault is seen the warning light is illuminated and a code set. The warning light will then go out when the fault is no longer seen, but the code will be set and retained in the computers memory. In OBD II systems the light does not go out until the fault is repaired and reset by the technician. This can create two problems for the motorist, first, if the warning light is set because of a loose gas cap, it will not go out when the cap is tightened. The car will have to be brought to a service facility to reset the light, at a cost to the motorist. Second the danger exists that when the car is brought into a repair facility, the technician might reset the light without actually repairing the fault. In this case the light will come back on again. It is important that the motorist be aware of the check enginelight, as well as all other dashboard warning lights and what they mean. This knowledge will help eliminate unnecessary costs due to unnecessary repairs. When any dashboard warning light comes on, check the owners manual before bringing the car to a repair facility.

Timing belt
Back to Car Care

Certain engines with overhead camshafts have timing belts that have a limited life span. Car makers use these belts instead of more durable chains because chains are noisier and cost more to manufacture. Your vehicle owner's manual will recommend at what mileage the timing belt must be replaced. These intervals range from every 60,000 miles to every 105,000 miles. To see what is recommended for your engine, click on the link at the bottom of this article.

The job of the timing belt is to turn the camshaft(s) at exactly 1/2 the speed of the crankshaft while maintaining a precise alignment. This means that the crankshaft will make two revolutions for every revolution of the camshaft. Engines will have at least one camshaft, or as many as four camshafts in some of the V-type engines. The camshaft causes the intake and exhaust valves to open and close in time with the pistons which move up and down in the cylinders. The valves must open and close at exactly the right time in relationship to the piston movement in order for the engine to run properly. For more information on how this works, go to "A Short Course on Engines"

(Article Continues below)

There are two types of engines that use timing belts. They are described as: "Interference Engines" and "Noninterference Engines" The difference lies in the proximity between the valves and the pistons. On an interference engine, if the timing belt slips even one notch, the piston can crash into an open valve causing serious engine damage by bending valves and breaking pistons. Non-interference engines will usually not self destruct, but in either case if the belt fails, the engine will immediately shut down leaving you stranded. The link at the bottom of this article will tell you which category your engine falls under.

Timing belts fail without warning and on some vehicles, are almost as hard to check as they are to change. In most cases, your only protection is to change the belt at the recommended intervals. Timing belt replacement is not a cheap job but it is far less costly than the alternative.

Some technicians may recommend that you replace the water pump during a timing belt job even if there is nothing wrong with it. This is because 90% of the labor to change the water pump has already been done with the timing belt job and some technicians consider it good insurance to replace the pump at this time. My feeling is that some water pumps can last the life of the car but many do fail and will cost big money to replace at a later date.

So ask your technician what his experience is with the water pump on your model car and look at how long you plan to keep the car. This way, at least you will be making an informed roll of the dice.

Timing Belt Replacement Recommendations by Make and Model.

My car won't start, what should I do?
by Charles Ofria With today's computer controlled cars, the possibility of a vehicle not starting when you turn the key is less likely then ever before. But it does happen, and when it does, it would help if you knew some basic tests and procedures that could allow you to determine the cause and often fix the problem yourself instead of relying on your local repair shop to bail you out.
The first step is to narrow down the cause of the nostart.

Let's go over the process of starting the car, so you have a better understanding of what is going on when you turn the key:

Here is what happens on a properly running car:

 

You sit behind the wheel and insert the ignition key into the switch. You then turn the key to the spring loaded start position. When you do that, the ignition switch engages the starter by connecting the battery to the electric starter motor which, in turn cranks the engine over. This can be easily heard and is referred to as cranking the engine over.

 

The next thing you will hear is the engine running, which is your signal to release the key. At that point, the engine is running and you are ready to place the transmission selector in Drive and be on your way.

Please note: This article outlines basic problems, but it is not meant to be a doit-yourself repair guide for resolving all possible no-start scenarios. If your mechanical experience is limited, this information may be helpful as preparation

for dealing with a repair shop.

A number of things can go wrong during the starting process. The following should help you distinguish exactly where the problem is occurring in order to determine what needs to be done to resolve the situation and get on your way.

Key will not turn: This can happen for a couple of reasons: The most obvious is that you are using a key not meant for that car or you have a worn out key. If you have a spare, try that one. A very common problem can occur when you park with the wheels turned all the way to one side and remove the key. When you try to turn the key to start, there is too much pressure on the steering lock to allow the key to turn. To correct this, force the steering wheel, first in one direction, then the other, while trying to turn the key. That should relieve the pressure and allow the key to turn.

Engine does not crank: When you turn the key to start, you may hear a single click or nothing at all, or you may hear a rapid series of clicks, like a woodpecker, or you may hear the cranking sound, but it goes very slowly. The most common cause for any of these is either a weak or dead battery, or a dirty or corroded connection to the battery. Before you go any further, turn your interior light on, then try to start the car. If the light is dim or goes dim when you turn the key to start, then Click here to find out what to do when you have a dead battery.

If the interior light is bright when you turn it on and doesn't change when you turn the key to start, the battery is probably ok. This condition can be caused by the following: (this list is sorted from most likely to least likely)



You do not have the transmission selector in park or neutral on an automatic transmission vehicle or there is a problem with the neutral safety switch. Try starting again with the transmission selector in Neutral.

  

You are not depressing the clutch pedal all the way down on a standard transmission vehicle or there is a problem with the clutch pedal switch. There is a problem with the ignition switch or connecting wiring. There is a problem with the starter motor or starter solenoid.

Engine cranks normally, but it does not fire: You turn the key to start and hear the starter motor crank the engine, but when you release the key, the cranking stops and there is silence. This means that the battery and starting motor are working properly, but the engine is not firing. If you continue cranking the engine over in this way, the battery will eventually run down and will need to be recharged, but the battery and starter are not the cause of your problem.

There are a number of causes for this type of no-start condition, the most common being that you are simply out of gas. Assuming that you have fuel in the tank, you will need to go through a series of tests to determine what is causing the problem. The testing procedure requires that you use specialized equipment in order to determine the problem area. There are three main tests in order to get you pointed in the right direction. You will need to test for Spark, Fuel and Compression, in that order. As soon as you see a problem in one of those areas, that is where you will need to concentrate your efforts.

Spark: An easy way to test for spark is with an inexpensive spark tester. This is a device that is readily available at most auto supply stores. You use it by simply holding it next to a spark plug wire. If you see the neon lamp flashing while someone cranks the engine, then you have spark and should move on to checking for fuel. If there is no spark, or a very weak spark, you will have to do a series of methodical tests that vary depending on the type of vehicle. You will need a repair manual for your car in order to get the correct diagnostic procedures. A good source for on-line repair information at a reasonable price is Alldata-DIY.

Fuel: First step here is to listen for the fuel pump running inside the gas tank. When you turn the key to run, you should easily hear the pump come on, run for a few seconds to build fuel pressure, then turn off. If you do not hear it, it could mean that the fuel pump or circuitry is bad. (Fuel pump failure is a common problem on modern cars.)

Fuel injected cars are very sensitive to proper fuel pressure. If the pressure is off, even by a few pounds, it will cause noticeable performance problems, or a no-start condition. To check for proper fuel pressure, you will need a fuel pressure gauge that is suitable for your type of system. A fuel injected engine (found on just about every vehicle less than 20 years old) produces very high fuel pressures and requires a fuel pressure gauge that reads up to 100 pounds per square inch. This type of gauge has a threaded connector that must match the pressure tap on your fuel rail. Since you are working with a highly combustible fluid which can be quite dangerous if you do not know what you are doing, you should leave this step to a pro.

Compression: If you know that you have spark and fuel, the next step is to check for compression. For this, you will need a mechanic's grade compression tester that will screw into a spark plug hole. You will need to remove the spark plugs and use the compression tester to test the compression on each cylinder. If the compression is very low on all cylinders, that is a sure sign that the timing belt (or timing chain depending on the engine) has failed and will have to be replaced.

Engine runs, but car will not move when put in gear: If the engine is running, but the car won't move when you put the transmission selector in gear, follow these steps:

Automatic Transmission: If you place the selector in Drive or Reverse, but the engine just races when you step on the gas and the car does not move or moves very slowly, it means that there is a problem with the

transmission or driveline. First thing to do is check the fluid level in the transmission. In most cars, you check the transmission fluid level with the engine running in Park. If the fluid level is very low, in short, you see no fluid on the dipstick, shut off the engine to avoid further damage to the transmission and call for a tow to a repair shop. In some cases, a leak can be repaired fairly easily without a large expense (assuming the transmission wasn't damaged by running with low fluid levels). If the fluid is full, there is a slight chance that the gearshift may have come disconnected, which means that you lucked out. Otherwise, you are most likely facing an expensive transmission rebuild.

Standard Shift Transmission: If you put the transmission in gear, but when you release the clutch, the car does not move or moves very slowly even though the engine is racing, it is probably time to replace the clutch. On some cars, you may be able to get by with a clutch adjustment, but if it has been slipping for a while, chances are that the friction surface of the clutch is burnt and will need to be replaced.

Dead Battery

One of the most common no-start conditions is caused by a dead battery. This does not automatically mean that the battery is no good, it only means that the battery has lost its charge for one reason or another.
The reason for the battery in a car is to provide temporary power to start the car or to run some accessories (like lights or radio) when the car is turned off. Once the car is running, the charging system (which consists of the alternator and voltage regulator along with the interconnecting wiring) will recharge the battery and provide all necessary electrical power to the vehicle. The battery then only serves as a backup if the vehicle requires more electrical current than the charging system can provide. This can happen when there is a high demand for electrical power, for instance on a cold, rainy night when you are in a traffic jam. In this case, your lights and wipers are on, the heater fan is blowing on high, the brake lights are being activated and the alternator is not spinning fast enough to keep the power coming. You may notice the lights dimming slightly, then brighten as you step on the gas. In these cases, a battery in good condition is more than capable of taking up the slack to keep everything going.

There are a number of reasons for a battery to become discharged so that it no longer has the power to start the engine.

The more common reasons for a dead battery are:

 

Forgetting the headlights turned on after you park the car. Forgetting a reading light or courtesy light turned on. This is easy to do since most cars have a feature that delays turning off the interior lights after you leave the car, so that you don't notice that you left a light turned on.



A corroded or loose connection between the battery and the cables attached to it.

  

A defective interior or trunk lamp switch that leaves the bulb lit. A defective charging system that does not replenish the battery's charge. An old battery that has lost its ability to maintain a full charge. Batteries have a life expectancy of 3 to 5 years, after which they should be replaced preventatively even if they are working well. Batteries have to work much harder during winter months when it is cold out. Sub freezing temperatures are when batteries usually begin to show signs that they are failing.

First, some important safety information: The automotive battery requires special handling. The electrolyte inside the battery is a mixture of sulfuric acid and water. Sulfuric acid is very corrosive; if it gets on your skin it should be flushed with water immediately; if it gets in your eyes, you should immediately flush them thoroughly with water and see a doctor right away. In this situation, time is critical. If you work with batteries often, you should have a mild solution of baking soda and water on hand and flush with that. The baking soda will neutralize the acid and minimize the damage. Remember: it is more important to flush immediately. Do not take the time to make up a solution first.

Sulfuric acid will eat through clothing, so it is advisable to wear old clothing when handling batteries. It is also advisable to wear goggles and gloves while servicing the battery. When charging, the battery will emit hydrogen gas; it is therefore extremely important to keep flames and sparks away from the battery.

Because batteries emit hydrogen gas while charging, the battery case cannot be completely sealed. Years ago there was a vent cap for each cell and we had to replenish the cells with distilled water when the electrolyte evaporated. Today's batteries (maintenance free) have small vents on the side of the battery; the gases emitted have to go through baffles to escape. During this process the liquid condenses and drops back to the bottom of the battery. There's no need to replenish or add water to this type of battery.

A car battery has two terminals either on top or on one site of the battery. On top terminal batteries, one post is slightly larger than the other post. The large terminal is the positive terminal and is marked with a prominent plus sign (+). The smaller terminal is the negative terminal and is marked with a minus sign ( -). On a side terminal battery, the cables are screwed to the terminals. They are also clearly marked with a + and - and are also color coded, Red for positive and Black for negative.

The negative terminal is directly connected to the metal body of the car as well as the metal engine block. This is also called the Ground. The positive terminal is insulated and goes to all the components that require power. The positive terminal must never come into contact with the body or you will cause a dangerous short circuit.

What to do when your battery is dead: The first thing you can do is check the battery connections. Find a pair of old gloves before you touch anything around the battery. Touching battery terminals with your hand will not give you a shock since we are dealing with only 12 to 14 volts and it would take more than that before you would feel it.

If however, you touch the battery terminal with anything metal and allow the metal to come into contact with any metal on the car, you will get a severe spark that could cause injury and possibly ignite the hydrogen gas causing an explosion. So if you plan to do this yourself, you should feel confident in your abilities and follow all the safety precautions, otherwise seek the help of a professional automotive technician.

If you still plan to do this yourself, here are some procedures to follow:

Once you are protected, grab each terminal and feel if the connection is loose on the battery. Only use a small amount of pressure so you do not damage the battery post. If you notice that one of the terminals is loose, just by moving it, you may be able to establish a good enough connection to start the car.

If it still won't start, you will need to either get a jump start or have the battery recharged using an external battery charger.

Getting a jump start: There are a couple of ways to boost, or jump start a car with a dead battery. You can get a Battery Booster Box, which is readily available in stores that sell automotive parts and accessories. This is a device with a rechargeable battery in it that has two large clamps that are used to connect to the dead battery. These booster boxes are recharged by plugging them into a regular wall outlet to keep them ready for use at a moment's notice. Many of them also have an air compressor that can be used to inflate your tires, and a search light to provide emergency light on the side of the road.

The other way is to use another car and connect its good battery to the dead battery using Jumper Cables. It is important to use good quality cables when trying to boost a car with a dead battery. Using thin, cheap cables may not allow sufficient amperage through. Furthermore, they can get very hot and fail, possibly causing serious burns or even fire.

When shopping for booster cables, look for heavy cable with insulated wire that is at least 6 gauge, with 4 gauge being better. (the lower the cable gauge, the thicker the wire). Make sure that the wire goes all the way through the clamp and is connected directly to the jaw. If the wire is connected only to the clamp grip, do not buy it. Good jumper cables will cost more than with professional quality cables costing or more. There are plenty of cables that cost as little as to . Stay away from those.

Booster cables have one black clamp on each end of one of the wires and a colored clamp, usually red or yellow, on each end of the other cable. When connecting the cable clamps to a battery, it is imperative that you always

clamp the positive clamp (Red) to the positive terminal (+) and the negative clamp (Black) to the negative terminal (-)

Batteries on newer cars are not always easily accessible, but when this is the case, they will have a battery tap somewhere in the engine compartment. The positive side will usually be clearly marked under a red plastic protective cover. The negative side may or may not be there, but you can always connect to the engine block or metal brackets that are directly attached to the engine.

Using another car for the jump start:

Important:

Check the owner's manual for both cars. On some vehicles, the manufacturer does not

recommend jump starting under any circumstances. Other vehicles have specific steps that must be taken before jump starting, such as removing a certain fuse before proceeding. Failure to follow these manufacturer's instructions can cause expensive damage to the vehicle electronics. If the jump start procedure in either owner's manual is different from the instructions listed below, you should follow the instructions in the owner's manual instead.

When using another car with a good battery, follow these steps:

       

Get the front of the car as close as you can to the front of the disabled car, making sure that the two cars do not touch. Shut both cars off and open the hoods. Wear suitable eye protection. Connect the positive (+) cable (Red) clamps to the positive battery terminal on each car. Make absolutely sure that you are connected to the positive terminals on both batteries with the same side of the cable (the connectors on each end of the cable are the same color (usually Red or Yellow) Next, connect the negative (Black) clamp to the negative terminal on the good battery. There should be no sparks) This is important. You will NOT be connecting the remaining clamp to the battery on the disabled car. Find a place on the dead car to connect the other negative clamp away from the battery, either on the engine block or a metal bracket that is directly attached to the engine. You most likely will see some small sparking. If you get a big spark, either there is something not connected properly, or the battery is shorted out, in which case you should not attempt a jump start until you replace the bad battery.

 

Once you have the cables connected, you can try to start the disabled car. If the only thing that was wrong was a discharged battery, the car should start up quickly. If the car is still hard to start, first disconnect the negative cable from the bad car, then check to make sure that there is a good solid connection at each of the remaining cable clamps, then reconnect the negative clamp on the disabled car's engine block and try again.



If the cables begin to get hot, discontinue the boost immediately: the cables are not heavy duty enough to do the job.

   

Once the disabled car is running, first remove the negative cable from the engine block of the problem car, then remove the negative cable from the other car. Finally, remove the positive clamps from both cars and close the hoods. It is a good idea to keep the problem car running until you are able to have the battery recharged, either by driving on the highway or with a battery charger. If you suspect that the battery did not discharge by something obvious, like forgetting the lights on, have the battery and charging system tested by someone with the proper equipment to do this, preferably a pro.

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