SUSPENSION SYSTEM • A suspension system is a set of mechanical connections, springs, and dampers that connect the wheels to the chassis. It has traditionally performed functions: managing the vehicle’s handling and braking for safety, and keeping passengers comfortable from bumps, vibrations, and other factors. Control arms : serve as the direct connection points between the front wheel assemblies and the vehicle's frame. Control arms are typically A-shaped, L-shaped, or wishbone-shaped. Control arm bushings: usually consist of an outer metal sleeve, a durable rubber steering knuckle: steering knuckle’s spindle locates and supports the inner and outer wheel bearings. Ball joints are components located on the front suspension system of a vehicle. They help form a connection between control arms and steering knuckles These four classes of springs are coil springs, leaf springs, coil over springs, and lowering springs. Dampers - commonly called shock absorbers - perform this function. A damper has a piston which moves inside a sealed, oil-filled cylinder with the up-and-down movement of the wheel. There are two general classifications of suspension systems known to date; dependent and independent. A dependent suspension system connotes that there is a beam or axle that connects the left wheel to the right so they work in tandem with each other. This classification of suspension can be sprung by either a combination of leaf springs and shock absorbers or coil springs and shock absorbers. The MacPherson strut is a step forward from the double-wishbone suspension. MacPherson’s key advantage is that all of the pieces that provide suspension and wheel control may be consolidated into a single system. Double wishbone suspension allows each wheel to act and react independently from the others. Trailing arm suspension is defined as the type of suspension where the axle or wheel “trails behind”. COOLING SYSTEM it is a set of components that enables the flow of liquid coolant to the passages in the engine block and head so as to absorb comustion heat. The Water Pump • Centrifugal- type. Rotates faster than crank, up to 10,000 gal. per hour. The Cooling Fan • Provides air flow with vehicle stopped • Provides increased air flow at low RPM or vehicle speeds. • Belt driven or Electric Belt Driven Cooling Fan Clutch • Limit actual fan speed no more than 2000 rpm • Engaged at low speeds • Disengaged at high speeds • Thermostatic (tem. sensitive). Flex Blade Fan • Fan blades flatten out at high speeds, reducing noise, increasing horse power. Electric Cooling Fan • Electric - 12v DC motor driven fan • Controlled in several ways - Engine coolant temp. (ETC) switch - A/C select switch - PCM controlled based on various inputs. • Fan turns On/Off at specific temps. Electro-Viscous Fan Clutch • PCM Controlled Fan speed • Sensors monitored to control speed: - ECT A/C request, VSS, IAT, Trans Fluid Temp, AAT • Solenoid controls fluid flow regulating fan speed •Internal hall effect sensor montitors fan speed. The Radiator • Transfer heat from coolant to the atmosphere • Two types: Vertical and Cross flow • Aluminum, brass, copper core; brass , copper or plastic tanks Radiator Pressure Cap • Regulates Pressure in the cooling system • Rated in psi - always replace with the same rating • Pressure Valve - allows liquid or vapor to escape • Vacuum Valve - as system cool, coolant can reenter the system. The Thermostat • Regulates engine coolant temperature • Related in degrees - 195 degrees most common • Solid Expansion design - wax pellet expands as temp increases, valve begins opening at rating and is completely open within 20 degrees. The Thermostat • Regulates engine coolant temperature • Related in degrees - 195 degrees most common • Solid Expansion design - wax pellet expands as temp increases, valve begins opening at rating and is completely open within 20 degrees. Coolant • Provides freeze and boil over protection, corrosion prevention and good heat transfer. • Ethylene Glycol based - recommended 50/50 mixture with water, poisonous he Heater Core • Small size radiator located in the dash, coolant circulate through it. A blower motor passes fresh air over it, heat transfers to the cooler air and into the cabin • Many vans and SUV have rear heating units. STARTING SYSTEM DIAGRAM The starting system includes the battery, starter motor, solenoid, ignition switch, and in some cases, a starter relay. An inhibitor (neutral safety) switch is included in the starting system circuit to prevent the vehicle from being started while in gear. BATTERY: An electrochemical device for storing energy in chemical form so that it can be released as electricity for cranking the engine and powering the electrical load. Also a group of electric cells connected together. STARTER MOTOR: A small, powerful electric motor that converts electrical energy from the battery into mechanical energy to spin the crankshaft and start the engine. SOLENOID: An electromechanical device which, when connected to an electrical source such as a battery, produces a mechanical movement. INHIBITOR (NEUTRAL SAFETY) *NEUTRAL-START SWITCH: A switch wired into the ignition switch to prevent engine cranking unless the transmission shift lever is in NEUTRAL. STARTER RELAY : An electrical device that opens or closes a circuit in response to a voltage signal. ALTERNATOR : Alternators are typically found near the front of the engine and are driven by the crankshaft, which converts the pistons’ up-and-down movement into circular movement. BATTERY CABLES : A starter motor requires a very high current to crank the engine, that is why it’s connected to the battery with thick (large gauge) cables. The negative (ground) cable connects the “-“ battery terminal to the engine cylinder block close to the starter. To start the automobile engine, the crankshaft must turn fast enough for air-fuel mixture to enter the cylinders. An electric starter or starting motor does this job. It converts electrical energy from the battery into mechanical energy that rotates the crankshaft. The positive cable connects the “+” battery terminal to the starter solenoid. 3 BASIC STARTING SYSTEM TROUBLES 1.) The engine does not crank. 2.) The engine cranks slowly but does not start. 3.) The engine cranks normally but does not start. (not caused by starting sys.) *problem “fuel or ignition sys./engine” OTHER COMPLAINTS Relay/solenoid-chattering Slow disengagement of the pinion from the ring gear. AUTOMOTIVE BATTERY CONSTRUCTION Automotive Battery : A lead-acid storage battery is an electrochemical device that produces voltage and delivers electrical current. The battery is the primary “source” of electrical energy used in vehicles today. It’s important to remember that a battery does not store electricity, but rather it stores a series of chemicals, and through a chemical process electricity is produced. Batteries- Primary or Secondary PRIMARY CELL: Because the chemical reaction totally destroys one of the metals after a period of time, primary cells cannot be recharged. Small batteries such as flashlight and radio batteries are primary cells. SECONDARY CELL: The metal plates and acid mixture change as the battery supplies voltage. As the battery drains the metal plates become similar and the acid strength weakens. This process is called discharging. By applying current to the battery in the reverse direction, the battery materials can be restored, thus recharging the battery. This process is called charging. Automotive lead-acid batteries are secondary cells and can be recharged.
