Engine lubrication systems have several important functions. It holds the adequate supply of oil to cool, clean, lubricate, and seal the engine. It also removes contaminates from the oil and delivers oil to all necessary areas of the engine through oil passages.
Excessive oil consumption can result from external and internal leaks, faulty accessories, piston rings, and valve guides. Internal leaks, which usually result in oil burning, are more difficult to diagnosis.
Synthetic oils are considered synthetic because the finished product does not occur naturally and it was made through a chemical, not a natural process. Synthetic oils have many advantages over mineral oils, including better fuel economy and engine efficiency by reducing friction. They have low viscosity in low temperatures and higher viscosity in warm temperatures and tend to have a longer, useful life. Synthetic oils cost much more then petroleum based oils and should not be mixed. Also it is best not to switch from petroleum oils to synthetic oils on an engine with many miles on it.
Drum brakes are still used on the rear wheels of many cars and light trucks.
The drum is mounted to the wheel hub. When the brakes are applied, a wheel cylinder uses hydraulic power to press two brake shoes against the inside surface of the drum. The resulting friction between the shoes lining and the drum slows the drum and wheel. The brakes’ anchor pin acts as a brake shoe stop, keeping the shoes from following the rotating drum, this creates a wedging action that multiplies the braking force.
Disc brakes are used today on the front wheels of cars and lights trucks and even on some rear wheel wheels.
Disc brakes offer four major advantages over drum brakes:
1. resistance to heat fade
2. resistance to water fade
3. increased straight line stopping ability
4. automatic adjustment
The typical rotor is attached to and rotated with the wheel hub assembly. Heavier vehicles generally use ventilated rotors. Splash shields protect the rotors and pads from road moisture and dirt. The calliper assembly includes cylinder bores and pistons, dust boots, and piston hydraulic seals. Brake pads are placed in each side of the calliper and together straddle the rotor.
There are two basic types of steering designs used in today’s cars. The Rack and Pinion steering input is received from a pinion gear attached to the steering column. This gear moves a tothed rack that is attached to the tie rods that move the wheels. Parallelogram steering linkage system includes the pitman arm, idler arm, links, tie rods, and in some designs a steering damper.
Caster is the angle of the steering axis of a wheel from the vertical, as viewed from the side of the vehicle. The forward and rearward tilt from the vertical line is caster. Caster is the first angle adjusted during an alignment. Tilting the wheel forward is negative caster; tilting the wheel backward is positive caster.
Camber is the angle represented by the tilt of either the front or rear wheels inward or outward from the vertical line as viewed from the front of the car. Camber is designed into vehicles to compensate for road crown, passenger weight, and vehicle weight. Camber is usually set equally for each wheel. Equal camber means each wheel is tilted inward or outward the same amount. Camber is affected by worn or loose ball joints, control arm bushings, and wheel bearings. Anything that changes chassis height also affects camber. Camber is adjustable on most vehicles.
Toe is the distance comparison between the leading edge and trailing edge of the front tires. If the leading edge distance is less, then there is toe in. If the leading edge distance is greater, there is toe out. Toe is as critical as a tire wearing angel. Wheels that do not track straight ahead have to drag as they travel forward. Excessive toe measurements cause a sawtooth edge on the tread surface from dragging the tire sideways. Excessive toe-in will cause tire wear on the outside edge. Toe-out causes wear on the inside edge.
The spring is the core of nearly all suspension systems. It is the component that absorbs shock forces while maintaining the correct ride height. If the spring is worn or damaged, the other suspension elements shift out of their proper positions and are subject to increase wear.
The springs take care of two fundamental vertical actions: jounce and rebound. JOUNCE occurs when a wheel hits a bump and moves up. When this happens, the suspension system acts to pull in the top of the wheel. REBOUND occurs when the wheel hits a dip or hole and moves downward. In this case, the suspension system acts to move the wheel in at both the top and bottom equally.
Shock absorber is added to each suspension to dampen and stop the motion of the spring jounce.
All of the vehicle’s weight supported by the suspension system is known as sprung weight. The weight of those components not supported by the springs is known as un-sprung weight.
The electrical system is perhaps the most important support system of a car or truck. Without a properly working electrical system, gasoline engines would not run. Electricity provides the needed spark for combustion, plus the power needed for starting, lighting and signalling, instrumentation, safety devices and many other accessories that you use every day.
Electrical vs. Electronics:
There is often confusion concerning the terms electrical and electronic. “Electrical” refers to wiring and electrical parts, such as generators, lights, and voltage regulators. “Electronics” means computers and other black box type items used to control engine and vehicle systems. The electrical system of an auto mobile includes the ignition, starting, charging, and lighting systems.
Open circuit refers to when a circuit has a break in the wire. Without a completed path, current cannot flow and the load or component cannot work.
Short circuit refers to an unwanted current path. Short circuits cause an increase in current flow. This increase in current flow can burn wires or even components.
High-resistance circuits refers to a problem occurring when there is unwanted resistance in the circuit. The higher than normal resistance causes the current flow to be lower than normal and the components in the circuit are unable to operate properly.