The D.E.P. Academy Driver Education Course


Vehicle Systems And Maintenance Page 2

The Engine Cooling System

  • The Moving Parts of an engine, and the explosion that happens in the piston chambers, create high temperatures. The coolant (antifreeze) mixture (with water) has to be cooled off. This happens in the cooling system.
  • The Coolant is one of several substances, a common one is ethylene glycol, that are mixed with water and circulated thru the car's cooling system. This mixture absorbs some of the heat created by the engine. The coolant also keeps the engine from freezing, and provides lubrication for the cooling system.
  • The radiator is a heat exchanger connected to the engine by an upper and lower hose.  When the coolant mixture travels through the radiator it transfers heat from the coolant to the atmosphere before the coolant is returned to the engine. A thermostat regulates the volume of coolant flow in order to keep the engine at  optimum operating temperatures.

The Vehicle Electrical System

  • The battery is the only source of electricity in your car. When you turn the ignition switch to start your car,  electricity is sent to the starter motor and to the spark plugs. Once your car is started the alternator keeps everything working. It also recharges the battery at the same time. The voltage regulator controls the amount of electricity that is being generated. The coil and the distributor generate and deliver the very high voltage needed by the spark plugs. The electricity is delivered through the car by electrical circuits for lighting, small electrical motors in your car, to operate computers that control certain functions, and the radio. Your car has fuses. These minimize the chance of fires by disconnecting circuits that may be drawing too much current.

The Steering Assembly

  • The steering assembly is the group of mechanisms that allow the driver to guide and direct a car. These include the steering wheel, steering column, steering box, linkages, and wheel support.
  • The steering wheel is used by the driver to direct the vehicle. Steering linkage converts the motion of the drivers hands into movements of the wheels.
  • The steering column is a metal shaft that connects the steering wheel to the steering box.
  • The steering box is a gearbox that is located at the lower end of the steering shaft. It converts the rotary motion of the steering wheel into the straight-line motion of the steering arms and steering knuckles.
  • The steering linkage are rods that carry movement to the steering knuckle. The steering knuckle is the part that is attached to the upper and lower control arms, or the kingpin, which allows the front wheels to pivot.
  • The power steering system makes turning the steering wheel much easier. It activates a hydraulic system which amplifies the force you exert on the steering wheel. In order for the system to work the engine must running. 

The Suspension System

  • A car's suspension system connects the wheels to the body and engine. Without the suspension system you would feel every stone on the road while driving. The suspension system reduces vibration.
  • The shock absorber is a friction device that controls and damps spring oscillations. Thus "shock absorbers" isn't accurate. Springs actually absorb road shock. Shock absorbers convert the energy of the springs into heat (by friction). Because shocks affect up-and-down wheel motion they are an important element of your car's riding and handling abilities.
  • The springs, leaf or coil, absorb the up and down motion of the car. The shocks keep the springs from continuing to bounce up and down. The strength of the springs determine the size of the load your car or truck will carry.
  • The linkage is a series of rods and levelers used to transmit motion from one component to the other.

The Braking System

  • Your vehicle has two braking systems. Both work independently of the other. The main system is operated by your brake pedal and is used to slow  down and stop your vehicle while you are driving . The parking brake, also known as the emergency brake is used to park on a downhill or uphill grade. It can also be used to stop your vehicle in case of emergency, but it is mainly used to stop your vehicle from rolling out of a parked position.
  • When you press your brake pedal, a piston in your master cylinder forces brake fluid through hydraulic lines to pistons in the wheel cylinders, where additional pistons provide the force to apply your brakes. Hydraulic fluid is stored in a brake fluid reservoir normally located in the engine compartment.
  • There are two types of brakes, drum brakes and disc brakes. Drum brakes slow your vehicle by using the friction of the brake shoe pushing against the inside of the drum, which is rotating with the wheel. Disc brakes slow your car by using the friction of a caliper pressing against a disc, which is rotating with the wheel. Both drum and disc brakes convert friction force to heat. If the brakes get too hot they cease to work because they can not dissipate enough heat.
  • Brakes will only slow your car while there is friction between the moving parts of the brakes. If the wheels lock, as is the case of a skid, the drums or discs are not moving and there will be no friction. The anti lock brake system is the system that keeps the brakes from becoming locked, by first sensing if they are locked, and then automatically, rapidly releasing and applying pressure. If you do not have ABS you can avoid having your brakes lock by rapidly applying and releasing pressure to the brake pedal.

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