PARTS
Wheel Bearing and Race
On most rear wheel drive vehicles there is an inner and outer wheel bearing for both front
wheels. The bearing fits inside the Race and its smooth surface allows the bearing to rotate
freely. When replacing wheel bearings you should also replace the race. Wheel bearings
should be re-packed with wheel bearing grease when performing a brake job, or if the wheels
have been submerged in water. A wheel seal is installed on the outside of the bearing to keep
the grease in the bearing area.
Wheel weight
Wheel weights are used to balance the tyres. Wheel weights are made of soft lead and come
in different sizes depending on the amount of weight the tyre needs to balance. A
computerized wheel balancer can determine where the weights need to be placed on the
wheel and how much weight is needed.
Just a small mount of weight can make a huge difference in ride performance. A tyre that is
out of balance will shimmy and vibrate and this vibration can be felt inside the car and in the
steering wheel. If a vibration is felt at one speed but not at another it is probably due to an
out of balance problem.
Inner CV Boot / Joint
The inner CV boot is connected to the CV (constant velocity) shaft’ at the other end is the
outer CV boot and joint. The purpose of the soft rubber boot is to protect the joint from road
debris and keep the special lubricating grease inside the boot to lubricate the joint. The boot
has to be soft and flexible because as you turn the wheels the boot stretches.
When the boot breaks the grease drips out and water and dirt get inside the joint causing
damage. A bad CV joint will usually make a clacking noise on hard turns. it can sometimes
be more economical to replace the entire CV shaft (comes with inner and out CV joints and
boots) with a rebuild unit than it is to replace 1 bad CV joint.
Thermostat
The function of the thermostat is to regulate the flow of coolant coming from the radiator to
the engine. Regulating the amount of coolant keeps the engine at a constant temperature.
Beware if your vehicle is imported, you may need the thermostat changed to operate correctly
in Australian conditions. Imported vehicles that have not had the thermostat changed have
been known to overheat & blow a head gasket. If the engine temperature is too cold, the
computer will enrich the fuel mixture (add more fuel) to compensate, if the temperature is too
high the engine will overheat and shut down. A thermostat can fail or “stick” due to rust or
calcium build up in the cooling system
Car Radiator
To properly check the condition of the radiator, some of the coolant should be removed, and
inside the radiator should be inspected for rust and calcium deposits that can build up and
restrict the flow of coolant.
Distributor Cap
The distributor cap distributes the electricity from the ignition coil to all spark plug wires.
The distributor cap is usually made of a hard plastic with internal copper contacts. The cap
takes a lot of abuse from high electrical voltages and should be inspected and or replaced
during a regular scheduled tune up. Most new cars today are distributor- less Ignition
Systems, (DIS) and do not have a distributor, distributor cap or ignition rotor.
Ignition Rotor
The rotor fits on the centre shaft of the distributor and is inside the distributor cap. When the
distributor turns the rotor the electricity from the ignition coil is sent through the rotor to the
individual contacts inside the distributor cap. The rotor can become worn and will need
periodic replacement. It is usually advisable to replace the distributor cap and rotor together.
Distributor Assembly
The distributor houses the distributor cap and ignition rotor and distributes the electricity
from the ignition coil to the individual spark plug wires. The distributor is turned by the
drive gear on the distributor connecting to the cam shaft inside the engine. The distributor is
usually found on the intake manifold assembly.
Ignition Leads
The ignition leads carry the spark from the ignition coil to supply the spark plugs with the
electricity needed to create a spark
The engine is the heart of your car, but instead of pumping blood, the engine pumps air and
fuel. The engines main function is to convert air and fuel into rotary motion so it can drive
the wheels of the car.
Pistons
Most common engines have 4, 6, or 8 pistons which move up and down in the cylinders. On
the upper side of the piston is what is called the combustion chamber where the fuel and air
mix before being ignited. On the other side is the crankcase which is full of oil. Pistons have
rings which serve to keep the oil out of the combustion chamber and the fuel and air out of
the oil.
Crankshaft
The crankshaft is connected to the pistons via a connecting rod. As the piston moves up and
down in the cylinder, it rotates the crankshaft and converts the straight line motion into rotary
motion. The crankshaft rides on bearings which can wear down over time. The bearings
support the crankshaft and also the rods which connect the pistons to the crankshaft. A loud
medium pitched knocking noise in the engine points to worn bearings most of the time. This
is usually a costly repair and involves removing the crankshaft and either machining the
surface where the bearings ride, or replacing the entire crankshaft. To prevent this type of
problem, use a high quality oil, change your oil at suggested intervals (3 to 6 months or 5000
to 10000kms is a safe number) and always maintain your oil level between oil changes.
Many times it is more economical to buy a replacement engine, than to have your engine
rebuilt when you have a crankshaft bearing failure. Your mechanic can give you a better idea
of costs involved.
Valve train
The valve train consists of valves, rocker arms, pushrods, lifters, and the cam shaft. The
valve train's only job is that of a traffic cop. It lets air and fuel in and out of the engine at the
proper time. The timing is controlled by the camshaft which is synchronized to the
crankshaft by a chain or belt.
Fuel tank
This is a holding tank for your fuel. When you fill up at a gas station the gas travels down the
filler tube and into the tank. In the tank there is a sending unit which tells the fuel gauge how
much is in the tank.
Fuel pump
On newer vehicles the fuel pump is usually installed in the fuel tank. Older cars have the fuel
pump attached to the engine or on the frame rail between the tank and the engine. If the
pump is in the tank or on the frame rail then it is electric and is run by your car’s battery.
Fuel pumps mounted to the engine use the motion of the engine to pump the fuel
Fuel filter
Clean fuel is critical to engine life and performance. Fuel injectors have tiny openings which
clog easily, so filtering the fuel is the only way to prevent this. Filters can be before or after
the fuel pump, sometimes both.
Fuel injectors
Most domestic cars after 1986 and earlier foreign cars came from the factory with fuel
injection. Instead of a carburettor to mix the fuel and air, a computer controls when the fuel
injectors open to let fuel into the engine. This has resulted in lower emissions and better fuel
economy. The fuel injector is basically a tiny electric valve which opens and closes with an
electric signal. By injecting the fuel close to the cylinder head the fuel stays atomised (in tiny
particles) so it will burn better when ignited by the spark plug.
Carburettors
A carburettor takes the fuel and mixes it with air, without computer intervention. While
simple in operation, they tend to need frequent tuning and rebuilding. This is why most
recent models have done away with carburettors in favour of fuel injection.
Exhaust manifold
The exhaust manifold attaches to the cylinder head and takes each cylinder’s exhaust and
combines it into one pipe. The manifold can be made of steel, aluminium, stainless steel, or
more commonly cast iron.
Oxygen sensor
All modern fuel injected cars utilize an oxygen sensor to measure how much oxygen is
present in the exhaust. From this the computer can add or subtract fuel to obtain the correct
mixture for maximum fuel economy. The oxygen sensor is mounted in the exhaust manifold
or close to it in the exhaust pipe.
Catalytic converter
This muffler like part converts harmful carbon monoxide and hydrocarbons to water vapour
and carbon dioxide. Some converters also reduce harmful nitrogen oxides. The converter is
mounted between the exhaust manifold and the muffler.
Muffler
The muffler serves to quiet the exhaust down to acceptable levels. Remember that the
combustion process is a series of explosions that create al lot of noise. Most mufflers use
baffles to bounce the exhaust around dissipating the energy and quieting the noise. Some
mufflers also use fibre glass packing which absorbs the sound energy as the gasses flow
through.
Exhaust pipe
Between all of the above mention parts is the exhaust pipe, which carries the gas through it's
journey out to your tail pipe. Exhaust tubing is usually made of steel but can be stainless
steel (which lasts longer due to it's corrosion resistance) or aluminised steel tubing.
Aluminised steel has better corrosion resistance than plain steel but not better than stainless
steel. It is however cheaper than stainless steel.
Water Pump
The water pump is either driven by the fan belt, or the timing belt on some newer vehicles.
The pump moves coolant from the radiator, through the engine, and back into the radiator.
The pump has a shaft with a pulley on one end and a pump rotor on the other end. When the
pulley is spun by a belt, the rotor moves the coolant.
Radiator
The radiator is a series of thin channels which the coolant flows through and is cooled by air
flowing through it. It is important to keep your coolant in good condition to keep the
channels open in the radiator. Following your manufacturer’s recommendation for changing
your coolant, will help keep your radiator in good shape.
Thermostat
The thermostat controls the flow of coolant through the engine. When your engine is cold, it
actually operates with less efficiency. So until the engine warms up to it's ideal temperature,
the thermostat keeps coolant from flowing. Your thermostat can fail in either an open or
closed condition. When it fails in the open position, your engine may actually run too cold
and you will have bad fuel economy. If the thermostat fails in the closed position, your
engine will overheat since no coolant will be flowing through the engine.
Hoses
The hoses carry the coolant from the radiator to the water pump and from the engine to the
radiator. Hoses are generally made of rubber and can deteriorate with time. Hose should be
flexible and not dry or rotted (check for tiny cracks in the hose)
Coolant
Coolant serves many purposes. Clean healthy coolant is a bright green colour. As it's
common name implies, coolant prevents overheating, but it also provides lubrication for the
water pump, increases boiling point of water, and keeps rust and scale from forming in your
cooling system. Coolant must be changed on a regular basis, check your owner’s manual for
the recommended schedule. PH level is critical to keeping your coolant from becoming a
metal eating liquid. When you check your coolant also check out the PH level and make sure
your coolant has not turned acidic. (In cooler climates Antifreeze is used, in place of coolant.
Antifreeze is a blue colour).