N1 Motor Trade Theory

Motor Trade Theory Downloaded from hlayiso.com N1

Module 1: Safety and health in the workshop TEACHING SAFETY MEASURES Safety is important in the workshop in order to save time, energy and even lives. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) GOOD HOUSEKEEPING Good housekeeping means there is a place for everything, and that everything is in its place. Good housekeeping is the basis for safe working conditions. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) ACCIDENTS An accident can be defined as an unforeseen and uncontrolled event caused by dangerous actions and dangerous conditions. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) HYGIENE AND SAFETY IN THE WORKSHOP It is important to ensure that workers work under healthy conditions and the responsibility for a hygienic workplace lies with employers and employees alike. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) SAFE HANDLING OF COMPRESSORS The compressor is driven by an electric motor, therefore all precautions related to electricity must be taken at all times. The compressor and the compressed air cylinder form a unit and should be housed in a separate room. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) SAFE HANDLING OF HYDRAULIC PRESSES AND APPARATUS The platform on which the workpiece is resting must be rigid, level and at right angles to the cylinder of the press. To prevent damage to soft material, the prescribed equipment and supports must be applied. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) HOISTS, JACKS AND TRESTLES A hoist designed to support the motor vehicle under an axle or other parts of the chassis should be placed so that the vehicle is raised evenly. Supports of different lengths are available for this purpose. Before the hoist is operated, care should be taken to support the mass of the motor vehicle evenly over the hoist. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) CARE, STORAGE AND SAFE HANDLING OF CUSTOMERS’ VEHICLES Make sure you return every vehicle you have worked on in a better mechanical condition and cleaner than when it came into the shop. When you repair a vehicle, always do the best job you can – a satisfied customer will bring his or her vehicle to you again. Downloaded from hlayiso.com www.futuremanagers.com

Module 1: Safety and health in the workshop (continued) TOWING A VEHICLE It is often necessary for you to collect a stationary or damaged vehicle to bring it to your workshop. All equipment required for towing must be in good working condition – equipment showing any faults or deficiencies must not be used. Downloaded from hlayiso.com www.futuremanagers.com

Module 2: Workshop measuring tools TOOLS IN THE MODERN WORKSHOP Modern workshops increasingly need electronic measuring and diagnostic equipment to deal with vehicles with many electronic and computerised systems. Downloaded from hlayiso.com www.futuremanagers.com

Module 2: Workshop measuring tools (continued) BASIC HAND TOOLS The most common tools are: • Spanners; • Hacksaws; • Pliers; • Files; • Screwdrivers; • Chisels; and • Hammers; • Centre and prick punches. Downloaded from hlayiso.com www.futuremanagers.com

Module 2: Workshop measuring tools (continued) SPECIAL WORKSHOP TOOLS AND EQUIPMENT Apart from the large variety of general hand tools, the competent motor mechanic also requires various special tools, instruments and equipment for dealing with particular tasks related to motor vehicles. This includes the torque wrench, brake spring pliers, battery pliers, piston ring compressor, piston ring spreader, valve spring lifter, vale grinder, and screw cutters. Downloaded from hlayiso.com www.futuremanagers.com

Module 2: Workshop measuring tools (continued) GENERAL TOOLS USED IN A WORKSHOP This includes but is not limited to: • Trestles; • Hydraulic jack; • Battery charger; • Manual and electrical hydraulic presses; • Motor car creeper and tool stand; and • Ball joint puller. Downloaded from hlayiso.com www.futuremanagers.com

Module 2: Workshop measuring tools (continued) MEASURING AND MARKING INSTRUMENTS The modern motor car is a precision-made mechanism with extremely fine tolerances. Even simple measuring tasks and settings such as valve clearances and backlash must be done with a great deal of precision. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components THE CYLINDER BLOCK The cylinder block is the main engine assembly that houses the crankshaft, the pistons and their connecting rods and is made to accommodate the forces generated by combustion. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) WATER JACKET These cylinder blocks are cast with intricate passages, called water jackets, through which the coolant is circulated by a pump. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) THE CYCLINDER HEAD The cylinder head serves as a “lid” for the cylinders. When the air-petrol mixture is compressed in the cylinders and ignited, the resulting pressure is contained by the cylinder head to force down the pistons. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) THE CRANKSHAFT The crankshaft is the main moving part of the engine. It is fitted into the cylinder block (or crankcase) and supported by a range of bearings. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) THE PISTON The piston and its valves form an air pump that creates a partial vacuum in the cylinder during the intake (down) stroke. The piston is a hollow cylinder, open at the bottom. The closed is called the piston crown and forms part of the combustion chamber. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) PISTON RINGS There are two types of piston rings: compression and oil control rings. Their number and arrangement vary from engine to engine, but generally all compression rings are fitted above the gudgeon pin while oil control rings are fitted below it. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) THE CAMSHAFT The main function of the camshaft is to convert the rotary movement of the crankshaft into the reciprocating movement of the valves and to open the valves at their pre-determined intervals. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) TIMING (CAMSHAFT) GEARS, CHAINS AND BELTS Camshafts are commonly driven by one of three arrangements from the front of the crankshaft – a gear train, chain or a toothed rubber belt. Camshafts run at half engine speed so the drive has to be stepped down from the crankshaft by having twice the number of teeth on the crankshaft gear, pulley or sprocket than on the camshaft. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) VALVE LIFTERS Valve lifters are used in pushrod (overhead-valve) engines and are designed to follow the shape of the pear-shaped cam on the camshaft and use this lift to push down and open a valve. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) PUSHRODS The pushrod has the simple function of transmitting the reciprocating movement of the valve lifter to the rocker that opens a valve. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) ROCKERS The rocker transmits the reciprocating movement of the pushrod to the valve stem. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) VALVES AND SPRINGS Four-stroke engines use valve springs to close their valves and to keep them closed for better sealing to prevent loss of pressure. The valve spring is kept onto the valve by means of a valve spring retainer and two halfmoon cotters. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) EXHAUST AND INLET MANIFOLDS The intake manifolds convey the fuel-air mixture from the carburettor or fuel injection system to the cylinders and help to promote vaporisation of the air- petrol mixture before admitting it to the cylinders. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) GASKETS AND SEALS Gaskets are used in assemblies such as gearboxes that are bolted together. A gasket or seal for an assembly that is not subject to heat can be a simple thick paper or cork pattern. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) CYLINDER HEAD Revolving shafts on the inside of an engine that end outside, such as the crankshaft or wheel bearings, must be sealed against oil loss and dust, and have seals made of a metal cover with a spring-loaded neoprene rubber ring that fits tightly around the shaft. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) CARBURETTOR Carburettors supply the internal combustion engine with an air-fuel mixture that varies in ratio to suit a range of conditions. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) IGNITION COIL The ignition coil transforms the 12 volt DC current from the battery to the high voltage (between 16 000 volts and 22 000 volts) required to create a timed spark across the spark plug gap that ignites the fuel-air mixture in the cylinder. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) SPARK PLUGS Spark plugs are screwed into the combustion chambers of petrol engines and provide the spark that ignites the mixture towards the end of the compression stroke. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) DISTRIBUTOR The distributor collects the high voltage sparks from the coil and conveys it to the different spark plugs in the correct order and at the right instant during the ignition cycle. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) STARTER MOTOR The starter is an electric motor that engages temporarily with the ring gear around the clutch plate to make the crankshaft rotate fast enough to start the engine Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) ALTERNATOR Modern cars use AC alternators instead of the older DC generators to provide electrical power for charging the car battery. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) BEARINGS AND BUSHES A modern internal combustion engine uses a variety of plain and ball or roller bearings as well as bushes to support all the moving parts and reduce play and friction. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) PISTON RINGS Bushes are plain one-piece bearings that tend to be longer than plain bearings. They are made from brass or phosphor bronze, which is porous and can be impregnated with oil to reduce friction, and are used around gudgeon pins, for valve guides and in gearboxes. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) FLYWHEEL Because the internal combustion engine delivers its power in spurts once every two or four revolutions, it needs a flywheel that can store some of the energy generated during a power stroke to keep the engine moving during the other stroke or strokes. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) FUEL PUMPS The fuel pump is used to supply fuel from the petrol tank to the carburettor or fuel injector at a pre-set pressure at all engine speeds. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) WATER PUMP The water pump is mounted at the front of the engine between the engine block and the radiator, and keeps the coolant circulating from the engine block and cylinder head and back. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) MATERIALS USED IN MOTOR VEHICLES The modern motor vehicle uses a wide variety of materials, some known for thousands of years like iron and copper, some dating from the space age like plastics and titanium. Iron and steel make up the bulk of the materials used in motor vehicles because the base metal iron is cheap, tough, easy to process and turn into a variety of alloys or heat treat for special applications. Downloaded from hlayiso.com www.futuremanagers.com

Module 3: Engine components (continued) PROPERTIES OF MATERIALS • Tenacity; • Elasticity; • Malleability; • Ductility; • Plasticity; • Toughness; and • Hardness. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains THE SINGLE PLATE CLUTCH Because internal combustion engines deliver most of their torque at higher revolutions, they need clutches that can be made to slip until the vehicle can move off. In manual transmissions the clutch must be let out smoothly and gradually feed in torque until the vehicle is moving fast enough to let the clutch out completely. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) THE CLUTCH ASSEMBLY The clutch assembly consists of a series of flat, smooth surfaces that can be locked together by friction when the clutch pedal is let out. These friction surfaces are the outside face of the flywheel, the double-sided pressure plate and finally the clutch plate that is operated by a foot pedal. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) PRESSURE PLATES There are two types of friction clutches in use: the helical spring-type pressure plate and the diaphragm spring type. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) THE CLUTCH PLATE The ideal clutch plate must perform the following functions: • It must create a firm link between the engine and the gearbox without slipping; • Be able to be completely released quickly and easily take up the drive smoothly without sticking or jerking; and • Be able to dissipate all the heat created by friction without damage, even under heavy loads. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) CLUTCH RELEASE MECHANISMS The linkages between the clutch pedal and the clutch assembly may be mechanical or hydraulic and some bigger models may have power assistance. Mechanical linkages must include some form of adjustment to compensate for wear and maintain the correct free play between the release bearing and the pressure plate fingers. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) THE CLUTCH RELEASE BEARING Two types of bearings are used to apply pressure to the pressure plate fingers and disengage the clutch: the graphite (or carbon) ring and the ball- bearing types. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) CLUTCH PEDAL FREE PLAY Clutch free play should be set according to the manufacturer’s instructions – normally 20 mm movement at the clutch pedal before resistance is felt will be sufficient. Downloaded from hlayiso.com www.futuremanagers.com

Module 4: Drive trains (continued) CLUTCH PROBLEMS Modern clutches are robust and give years of use under normal conditions. When problems do occur they usually take the following forms: • Slipping clutch; • Dragging clutch; • Grabbing clutch; and • Shuddering clutch. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines TYPES OF ENGINES The four-stroke engine is used in the following: • Motorcars and motorbikes; • Boats; • Trucks; • Lifting equipment; • Water pumps; and • Generators. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE FOUR-STROKE PETROL ENGINE The engine comprises a cylinder block in which a cylinder is bored to accommodate the piston and piston rings. A crankshaft is mounted on one side of the cylinder block, which is enclosed in an oil pan/ sump. The included space is called the crankcase. The oil pan contains a specified quantity of engine lubricating oil. The piston is connected to the crankshaft by a connecting rod and Downloaded froma gudgeon pin. hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE THREE-PORT TWO-STROKE PETROL ENGINE Two-stroke engines are widely used by motorcycles, lawn mowers and motorboats. The construction of this engine is similar to that of the four-stroke petrol engine. However, the three-port two-stroke engine does not have valves. Instead there are the intake port, the exhaust port and the transfer port, all of which are closed and opened by the moving piston. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) ADVANTAGES OF PETROL INJECTION IN COMPARISON TO CARBURETTORS • The air fuel mixture may be measured exactly at all engine speeds. • Ignition knock is improbable. • Air pollution is reduced. • More than 100% volumetric efficiency is possible. • Higher CR’s may be used because of better mixture control. • Icing of inlet manifold cannot occur Downloaded as only from air passes through. hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) COMPRESSION IGNITION ENGINES (DIESEL ENGINES) Compression ignition engines operate as a result of fuel burning in the cylinder and are dependent on the amount of heat generated by the burning fuel. This heat energy is then converted into useful work. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE FOUR-STROKE C.I. ENGINE The engine consists mainly of the following components: • Cylinder; • Main bearings; • Piston; • Crankshaft timing gear; • Connecting rod; • Camshaft; and • A hinge action; • Valve mechanism. • Crankshaft; Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE TWO-STROKE C.I. ENGINE There are two basic types of engines: 1. Engines with ports in the bottom end of the cylinder which are used to scavenge exhaust gases and admit the fresh air charge. (Port-type) 2. Engines where the intake port is in the bottom end of the cylinder and the exhaust port is in the cylinder head. The closing and opening of the exhaust port in this case is controlled by poppet valves. (Uniflow-type) Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE PORT-TYPE TWO-STROKE ENGINE The cylinder is designed with ports at the side of the cylinder, more or less at the end of the stroke of the piston. The intake ports are designed so that the fresh air charge is directed in a spiral movement towards the cylinder head. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE ‘UNIFLOW’-TYPE TWO-STROKE ENGINE The cylinder is designed with intake ports only, which are cut around the whole bottom end of the cylinder. When the piston is at b.t.c., the ports are exposed. The cylinder head is equipped with two exhaust ports which are controlled by poppet valves. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE OPPOSED-PISTON TWO-STROKE DIESEL ENGINE The two-stroke diesel engine is also used to power large machines and ship engines. It can be seen as two diesel engines with their cylinder heads removed, bolted together head to head. The combustion chamber is formed by the space between the two pistons where the injector is mounted as well. Downloaded from hlayiso.com www.futuremanagers.com

Module 5: Heat engines (continued) THE ROTARY ENGINE The rotary engine consists of the following main components: • An oval rotor casing with ports, a water jacket and flat end casings; • A triangular rotor with curved sides and flat ends; • An eccentric crankshaft; • An annular gear inside the rotor that engages with fixed gear on one end casing; and • Inlet and exhaust ports and sparkfrom Downloaded plugs inhlayiso.com the casing. www.futuremanagers.com

Module 6: Mounting an engine POSITIONING AND MOUNTING AND ENGINE Probably the most common arrangement for passenger vehicles used today is the front-engine, front-wheel drive (FWD) transverse engine type. When it comes to commercial vehicles, the front-engine, rear-wheel drive (RWD) is the rule, while every sports car worthy of the name has a mid- engine driving the rear wheels, or even all-wheel drive. Downloaded from hlayiso.com www.futuremanagers.com

Module 6: Mounting an engine (continued) MOUNTING AN ENGINE • Four-point system: The engine is attached to the frame at four different points. This system is mainly used for heavy vehicles and tractors. • Three-point system: The engine is attached to the frame at three different points. This system is used in passenger cars and light motor vehicles. Downloaded from hlayiso.com www.futuremanagers.com

Module 6: Mounting an engine (continued) FRAMES A clear distinction should be drawn between the A-frame and chassis of a vehicle as these two concepts are very often interpreted incorrectly. The chassis of a vehicle includes the front and rear wheel suspension, the steering system, brake system, engine, gearbox, the drive system and the frame. The bodywork is excluded. Downloaded from hlayiso.com www.futuremanagers.com

Module 6: Mounting an engine (continued) BEAMS In order to make the framework of a vehicle as light as possible, various hollow beam profiles are used for manufacturing these frames. They are designed to resist bending and flexing. O-beams are often used as cross members in ladder frames. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems LUBRICATION When gases condense after cooling, they become all the types of petroleum fuels and lubricants as we know them. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) LUBRICANTS After distillation, the lubricating oil stock contains a number of undesirable non-lubricating compounds such as gum, tar and wax. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) ENGINE LUBRICATING SYSTEMS Moving components in an engine are protected by the engine oil, which prevents metal-to-metal contact by placing a very thin film of oil between moving surfaces. Supplying enough of the right oil to an engine is important because without lubrication, moving parts will overheat, seize and fail. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) OIL CONTROL METHODS There are several basic oil control devices: • Oil seals and retainers; • Oil restrictors; • Gaskets or packing; • Oil throwers; and • Oil turbines. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) OIL PRESSURE IN AN ENGINE In the modern engine it is not only necessary to get the oil between bearing surfaces, but also to keep it there under pressure so that an oil cushion is maintained between the surfaces. Oil is necessary to cool friction bearings by a constant supply of cooler oil. The oil is drawn from the sump by the oil pump and fed under pressure to the parts. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) ABNORMAL OIL CONSUMPTION Oil can be lost out of the engine in three ways, namely: • Burning in the combustion chamber; • Leaking out pst gaskets and seals in liquid form; and • Leaking through the breather pipe as a vapour. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) CRANKCASE VENTILATION The function of crankcase ventilation is to remove harmful evaporates that contaminate the oil from the crankcase. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) OIL COOLERS It is necessary to fit oil coolers on some vehicles to prevent harmful rises in oil temperature during heavy engine running conditions. The oil is circulated by a pump and passes through the cooler, where heat is extracted on the heat exchanger principle. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) OIL FILTERS The function of the oil filter is to trap as much as possible of the larger solid impurities in circulation with the lubricating oil; the oil filter does not actually clean the oil. Downloaded from hlayiso.com www.futuremanagers.com

Module 7: Lubrication systems (continued) OIL PUMPS The oil pump draws oil from the sump and supplies it under considerable pressure to the different engine components, especially plain bearings such as the mains big-end and camshaft bearings. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems TEMPERATURE CONTROL The internal combustion engine is a heat engine that produces a large amount of heat while it works, so much that it will destroy itself unless this heat is absorbed – the function of the cooling system is to remove as much of this heat from an engine as possible, and fast enough, to keep its temperature within safe limits and avoid permanent damage. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) DIRECT WATER COOLING Water cooling without air as a cooling medium is used in marine and water- pump engines. A positive water pump circulates water from an external source, which may be a river or the sea, through the water jackets of the engine and directly back to the source, so the water is not re-circulated. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) DIRECT AIR COOLING (AIR-COOLED) Large volumes of air must be brought into direct contact with the hot surfaces of an engine and then removed as quickly and efficiently as possible to keep it cool. This direct air cooling, or simply air cooling, is well known from its use in motor cycles and petrol lawn mowers, for instance. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) INDIRECT AIR COOLING (WATER COOLED) These engines need a complicated system of water jackets cast into the cylinder block and cylinder head, a water pump, a radiator and its hoses, a fan and a thermostat, and some way of heating the vehicle’s interior from the engine coolant. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) RADIATORS The radiator is the component that exchanges heat between water and air. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) WATER PUMPS • The positive pump consists of a housing of aluminium alloy or cast iron containing a centrifugal impeller mounted on a set of bearings. • The impeller pump acts on the same principle as the positive pump except that the impeller is inserted directly in the water jacket, while the housing carrying the shaft bearings with their water seal and the by-pass and inlet ports is bolted to the engine block. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) THERMOSTAT It is the function of the thermostat to regulate the cooling system to achieve quick heating and a constant working temperature. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) THE BYPASS The bypass system allows the water to re-circulate between the cylinder head and the cylinder block while the thermostat is closed. The bypass port connects the water outlet port in the cylinder head with the inlet port of the water pump. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) WATER DISTRIBUTING TUBES Special distribution tubes with holes or nozzles are built into water jackets at suitable spots in order to direct jets of coolant onto these components. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) RADIATOR SHUTTERS Radiator shutters are usually operated by thermostats, although there are also manual systems, where a blind is pulled across the radiator opening. Radiator shutters have failsafe devices that open them to prevent overheating if the thermostats should fail and there is usually a manual override as well. Downloaded from hlayiso.com www.futuremanagers.com

Module 8: Cooling systems (continued) OVERHEATING There are many reasons for an overheating engine, mostly because of coolant loss in water-cooled engines and failed fans or shrouds in air-cooled models. Overheating in an engine can cause severe damage – cylinder heads can warp, pistons can be destroyed by pre-ignition and bearings can “run”. Downloaded from hlayiso.com www.futuremanagers.com

Module 9: Batteries BATTERIES The battery stores electricity in the form of chemical energy, which can be converted back to electricity when needed. The battery loses its chemical energy when supplying electricity, but it is recharged by the vehicle’s alternator (or generator) while the engine runs. Downloaded from hlayiso.com www.futuremanagers.com

Module 9: Batteries (continued) BATTERY CHECKING AND CHARGING • Electrolyte levels must be checked occasionally and the battery topped up with distilled water to the specified upper level marked on the case. • To check the battery charge, the specific gravity of the electrolyte must be measured and a load test performed. The battery condition can be determined from the results of both. • Batteries may need to be charged before putting into a vehicle. There are two methods,Downloaded a quick charge or afrom slow charge. hlayiso.com www.futuremanagers.com

Module 9: Batteries (continued) SULPHATION Sulphation is the name given to a particular lead sulphate crystal formation that grows on the plates of a battery, and which adversely affects the electrical performance of the cells. Downloaded from hlayiso.com www.futuremanagers.com

Module 9: Batteries (continued) TESTING A BATTERY WITH A V METER A battery voltage test is the only test that can be used on maintenance-free batteries. • Connect the meter across the battery terminals and turn on the car’s headlights or heater fan to provide a light load. • Take a reading with the meter. • A well-charged battery should register over 12 V, but if the meter reads about 11,5 V, Downloaded the battery is not necessarily defective. from hlayiso.com www.futuremanagers.com

Module 9: Batteries (continued) CARE AND MAINTENANCE OF THE BATTERY Battery maintenance should be done periodically during engine tune-ups, lubrication services, or at any time when symptoms indicate battery problems. Downloaded from hlayiso.com www.futuremanagers.com

Module 9: Batteries (continued) REMOVING A BATTERY • Remove the cable carefully so that you do not damage the terminals. • Loosen the battery nut, open up the connector’s open end sufficiently and pull the cable straight up. • Loosen the battery clamp nut, remove the bolt, remove the clamp, and lift the battery case. • Lift the battery case straight up - tilting it to one side may allow the electrolyte to Downloaded spill out. from hlayiso.com www.futuremanagers.com

Module 9: Batteries (continued) CONNECTING BATTERIES IN SERIES OR PARALLEL • Series circuit: When two 12V batteries are connected in series, they form a 24V battery that has the capacity for starting heavy-duty vehicles equipped with a 24V system. • Parallel circuit: When two 12V batteries are connected in parallel, they form a 12V battery with more power, greater cranking ability and a longer useful life than a single 12V battery. Downloaded from hlayiso.com www.futuremanagers.com

Module 10: Wheels and tyres TYPES OF WHEELS AND RIMS • Disc wheels; • Pressed-steel disc wheels; • Cast light-alloy disc wheels; and • Single-piece rim wheels. Downloaded from hlayiso.com www.futuremanagers.com

Module 10: Wheels and tyres (continued) TYRES AND TUBES The modern car tyre is a complicated structure, designed to provide all the features motorists demand, such as long life, good braking and road holding and comfort. Downloaded from hlayiso.com www.futuremanagers.com

Module 10: Wheels and tyres (continued) TUBES TYRES AND TUBELESS TYRES A tyre with a tube has a separate rubber inner tube to retain pressurised air inside the tyre. The tyre valve, which protrudes through a hole in the wheel rim, is bonded to the inner tube. Tubed tyres are being replaced by tubeless tyres as tyre designs progress. The tubeless tyre has no inner tube. The pressurised air is held in by an inner liner, a specially- formulated thick rubber lining with high sealing effectiveness. Downloaded from hlayiso.com www.futuremanagers.com

Module 10: Wheels and tyres (continued) TYRE PRESSURES AND LOADS It is important to check the pressure of the tyre while the tyre is cold. If a tyre is checked when hot and the pressure is found to be greater than the manufacturer’s specifications, air should not be let out (‘bled’) from the tyre because if this is done, the ‘cold’ pressure will be less and the tyre will be under-inflated when it cools down. Downloaded from hlayiso.com www.futuremanagers.com

Module 10: Wheels and tyres (continued) INFLATION AND TYRE WEAR Although tyres are made up of more or less airtight materials, they still allow minute quantities of air to leak over time. Tyre pressures must therefore be checked regularly and adjusted to the specified pressure. Downloaded from hlayiso.com www.futuremanagers.com

Module 10: Wheels and tyres (continued) MATCHING TYRES A dual-wheel arrangement: A tandem-wheel arrangement: Downloaded from hlayiso.com www.futuremanagers.com