Clutch The fan clutch is a small fluid coupling with a
thermostatic device and controls a variable-speed fan. It ensures
that the fan will rotate at just the right speed to keep the engine
from overheating, and reduces drive to the fan when it is no longer
needed. The fan clutch has a fluid coupling partly filled with
silicone oil designed for just that purpose. When the temperature of
the air passing through the radiator rises, the heat alerts a bimetal
coil spring to "uncoil" or expand. When it expands, it
allows just a little more oil to enter the fluid coupling, so the
fluid coupling starts to rotate the fan. If the air coming through
the radiator is cool, the opposite happens; the coil spring
contracts, the oil leaves the fluid coupling and the fan slows.
Slowing the fan when it is not needed reduces fuel consumption, makes
less noise and saves engine power. Sometimes a flat bimetal strip
spring is used instead of a coil spring; it bows out and in when the
temperature rises and drops, letting oil in and out of the fluid coupling.
Idle The higher speed, 1,100 to 1,500 rpm, at which an engine
idles during warm-up, when first started.
Cam A cam-shaped lever on the carburetor that provides
fast-idle action when the engine is cold.
Screw A screw in the carburetor linkage to adjust fast-idle speed.
solenoid operating in conjunction with an automatic choke to open
the throttle slightly when the choke is in operation
outside lane (far left lane in North America, etc. or the far
right lane in Britain, Australia, etc.).
called the "passing lane"
Blade A thin strip or blade of hardened steel, ground to an
exact thickness, used to check or measure clearances between parts.
Cap (Brake Fluid Reservoir Cover) The cap on the brake fluid
reservoir has a hole for air, or is vented, to allow the fluid to
expand and contract without creating a vacuum or causing pressure. A
rubber diaphragm goes up and down with the fluid level's pressure,
and keeps out any dust or moisture.
A thin metal object projecting from a surface and is used to
dissipate heat. It is found on radiators and air-cooled engines.
Wings and airfoils used to improve a vehicle's aerodynamics,
stability, or possibly aesthetics.
Drive This is the end of the drive train before power is
transmitted to the wheels. In a typical car, the engine (or electric
motor) transmits its power through some sort of clutch into a
transmission. Then the power is transmitted to differential gears
that adjust the engine speed to the most efficient use intended.
These final drive differential gears are either at the front axle or
rear axle, depending on the vehicle's layout. A typical family car or
one intended for high speeds will have a low numerical ratio, to give
it speed and good fuel efficiency. A truck or performance car is
likely to have a high numerical ratio for better pulling power or for
Drive Gear The last gear in a drivetrain before the
driven wheels. Usually it is in the differential.
The partition dividing the engine compartment from the passenger
compartment on a car or truck.
Oder The order in which the engine cylinders fire, or
deliver their power strokes, beginning with the number one cylinder.
spark plug in each cylinder fires in a particular order, which is
unique to the engine design.
example, the firing order for a small-block or big-block Chevy V8 or
a Chrysler V8 is 1, 8, 4, 3, 6, 5, 7, 2.
Coupling On a manual
transmission, there is a mechanical connection between
the engine and transmission
through the clutch.
On an automatic transmission
a fluid coupling provides a viscous fluid to connect the engine
output and the transmission. It transfers engine torque to the
transmission input shaft through the use of two units with vanes
(called a "torus") operating very close together in a bath
of oil. The engine drives one torus causing it to throw oil outward
and into the other torus which then begins to turn the transmission
input shaft. A fluid coupling cannot increase torque above that
produced by the crankshaft. Buick's Dynaflow is an example of this
kind of coupling.
A large, heavy iron or steel disc attached to the rear of an engine
crankshaft in order to provide sufficient centrifugal force to smooth
the power impulses from the cylinders
Cycle (Four-Stroke Cycle) An internal-combustion engine
that requires two revolutions per cylinder or four piston strokes to
achieve a power stroke: internal stroke, compression stroke, power
stroke, exhaust stroke. More efficient than the two-stroke-cycle engine
Drive (4WD) A type of drive system in which both front
wheels are connected to its own differential and axles, and both back
wheels are connected to its own differential and axles. Between these
two differentials there is a transfer case which allows you, in the
case of part-time four wheel drive, to switch between two-wheel drive
and four-wheel drive. In full-time four-wheel drive power is sent to
The basic structure of the vehicle is the frame and it provides
a good anchor point for the suspension system. There are two types of
frames; integral frames, or 'unibody', and conventional frames. A
conventional frame is basically a 'one-piece' frame; or two
'one-piece' frames fastened together. These frames are extremely
rigid to keep all the parts of the car in perfect alignment, which
are attached to it. It is constructed of heavy steel and welded or
cold riveted together. Cold riveting keeps the rivets from shrinking
after they cool off. The integral, or unibody, frame is just the
opposite. With this type of frame, the body parts are used to
structurally strengthen the entire car, and all of the sections are
welded into one piece. Sometimes the parts of the body and the
suspension system are attached and reinforced. Also, some unibody
frames have partial front and rear frames for attaching the engine
and suspension members.
play The amount of travel before any action takes place.
The "looseness" in a linkage, or an assembly of parts,
between the initial application of force and actual movement. For
example, the distance the brake pedal moves before the pistons in the
master cylinder are actuated.
apron: The panel behind and below the front bumper, joining the
bottom ends of the front fenders
Axle The axle to which the front wheels are attached
split: A dual-circuit braking system in which one circuit brakes
only the front axle while the other circuit brakes only the rear axle.
Axle and Rear Axle split
and Rear-Axle split
dual-circuit braking system in which each circuit brakes both the
front axle and the rear axle
bumper: A guard which protects the front of a vehicle. See bumper
and rear bumper.
differential: differential in the front axle of a four-wheel drive vehicle
end: body area incorporating the leading edge of the fenders, the
headlights, radiator grille and bumper, i.e., the full area that
makes up the frontal appearance of the car
end alignment: See front-end alignment.
alignment: The adjustment of the camber and caster of the front
wheels. See alignment.
impact: An impact as the result of a head-on collision
engine: A vehicle with its engine located at the front of a vehicle
above the front suspension. This is the most common layout, which may
be combined with either rear-wheel or front-wheel drive. Also see
mid-engine car and rear engine
fender: body section covering the front wheels, originally separate;
but now in most cars faired in and part of the body shell
fork: See fork.
forks: See fork.
nose section: The front section of a car's body that uses one single
structure to make up the front end, i.e., including the radiator
grille surrround, both fenders, front apron, etc. front panel: A
panel joining the front fender and forming a mounting for the
headlights, grille, and air ducts into the engine compartment, which
is often identical with the front apron where no separate apron is
fitted below the front panel. Also see lower front panel
pillar: See a-pillar
pipe: The first section of the exhaust system from the exhaust
manifold to the silencer (or front silencer where there are two).
Also see twin front pipe
The closed position of a stem type service valve to isolate the
compressor. The system should never be operated with the valves in
seat: seat in the front of passenger cabin for the front seat passenger
seats: The front passenger's and driver's seats
silencer: first and main silencer in an exhaust system where there
spoiler: The air deflector on the front of a car, aerodynamically
designed to cut the wind resistance around the car, for improved
handling control, stability, traction, and better fuel economy
suspension: The springs, shock absorbers, linkages, etc. which
support the front wheels. See independent front suspension.
triangle: Actually a quadrilateral with one short side, it is the
section of a bicycle frame that consists of the head tube, the top
tube, the seat tube, and the down tube. Also called "main triangle."
wheel drive: See front-wheel drive.
drive: (FWD) A vehicle that is pulled by its front wheels rather
than being pushed by its rear wheels. The driveshaft and center floor
hump is eliminated in front-wheel drive cars. The engine is located
over the driving wheels so that it gains better traction in snow.
Wear on the front tires can be severe.
wheel tire clearance: The distance between the tire and the closest
point on the vehicle laterally, longitudinally and vertically,
checked lock to lock and all intermediate points.
wing: British term for front fender
Suspension The springs,
which support the front wheels.
Wheel Drive (front-wheel drive)
A vehicle that is pulled by its front wheels rather than being
pushed by its rear wheels. The driveshaft and center floor hump is
eliminated in front-wheel drive cars. The engine is located over the
driving wheels so that it gains better traction in snow. Wear on the
front tires can be severe.
combustible material used to produce energy. One of the essential
factors in a combustion engine
(Fuel, Air, Proper proportion of mixture, compression, timing, spark).
Air Mixture (Fuel-Air
combination of vaporized fuel and air which is brought into the
cylinder through the carburetor or fuel injectors. When it is
compressed and ignited, it produces the power needed to drive the engine.
Air Ratio The amount of fuel in comparison with the amount
of air. This is the reciprocal of the
Delivery System The various components that move fuel from
the gas tank to the engine. This typically includes a fuel pump, a
considerable length of fuel line (hard tubing) and a fuel
filter. Once the fuel reaches the engine compartment, it travels
through the fuel injection system and into the engine to get burned
along with air during the combustion process (or, in older or race
vehicles, through one or more carburetors and into an intake manifold).
a filter, the jets and orifices in the carburetor will become clogged.
Filter A device that removes impurities from the fuel before it
gets to the carburetor. It is usually found near the carburetor in
the fuel line that comes from the fuel pump (in-line fuel filter), or
inside the carburetor (integral fuel filter) or fuel pump (integral
fuel filter). This unit must be cleaned or replaced on a regular
basis, usually once a year or it will become clogged and restrict
fuel to the carburetor.
instrument, usually located on the dashboard or center console,
which indicates the amount of fuel in the fuel tank. Most gauges have
a needle which fluctuates between "E" (empty) and
show a digital readout of how many gallons or liters left in the
tank. Also called "gas gauge."
Injection (FI) A fuel system that uses no carburetor
but sprays fuel either directly into the cylinders or into the intake
manifold just ahead of the cylinders. It uses an electronic sensing
device to deliver the correct amount into the combustion chamber.
Throttle-body injection locates the injector(s) centrally in the
throttle-body housing, while port injection allocates at least one
injector for each cylinder near its intake port.
throttle body injection (TBI) systems that appeared on cars and
trucks in the '80s were essentially electronically controlled
carburetors, which squirted fuel into the intake manifold, rather
than apportioning it to each individual cylinder.
Injectors The part of a fuel injection system that squirts
fuel into an engine. When a vehicle has been modified for
significantly enhanced airflow in the intake system, it sometimes is
necessary to swap to higher-flow fuel injectors, so they can deliver
sufficient fuel to maintain the ideal air/fuel ratio.
metal, plastic, or rubber hose or pipe through which the fuel passes
from the fuel tank to the fuel pump to the carburetor or fuel
measurement or calculation of the number of miles per amount of fuel
- usually measured in miles per gallon.
mixture of gasoline and air. An average mixture, by weight, would
contain 16 parts of air to one part of gasoline.
Pump The fuel pump has three functions: to deliver enough
fuel to supply the requirements of an engine under all operating
conditions, to maintain enough pressure in the line between the
carburetor and the pump to keep the fuel from boiling, and to prevent
vapor lock. Excessive pressure causes the carburetor float needle off
its seat its seat resulting in high fuel level in the float chamber,
leading to high fuel consumption. Highest pressure occurs at idling
speed and the lowest at top speed.
bottom of the tank contains a drain plug so that tank may be drained
Tank The fuel tank stores the excess fuel until it is
needed for operation of the vehicle. The fuel tank has an inlet pipe
and an outlet pipe. The outlet pipe has a fitting for fuel line
connection and may be located in the top or in the side of the tank.
The lower end is about one-half inch above the bottom of the tank so
that collected sediment will not be flushed out into the carburetor.
An electrical device which protects a circuit against accidental
The typical fuse contains a soft piece of metal which is calibrated
to melt at a predetermined current flow (expressed as amps) and break
link A circuit protection device consisting of a conductor
surrounded by heat-resistant insulation. The conductor is smaller
than the wire it protects, so it acts as the weakest link in the
circuit. Unlike a blown fuse, a failed fusible link must frequently
be cut from the wire for replacement.