【文章內(nèi)容簡介】 of some kind is necessary in any internal bustion engine.There are generally two different types of cooling system: watercooling system and aircooling system. Watercooling system is mon. The cooling medium, or coolant, in them is either water or some lowfreezing liquid, called antifreeze. A watercooling system consists of the engine water jacket, thermostat, water pump, radiator, radiator cap, fan, fan drive belt and necessary hoses.A watercooling system means that water is used as a cooling agent to circulate through the engine to absorb the hot and carry it to the radiator for disposal. The engine is cooled mainly through heat transfer and heat dissipation. The heat generated by the mixture burned in engine must be transferred from the iron or aluminum cylinder to the water in the water jacket. The outside of the water jacket dissipates some of the heat to the air surrounding it, but most of the heat is carried by the cooling water to the radiator for dissipation. When the coolant temperature in the system reaches 90 176。C, the thermostat valve open fully, its slanted edge shutting off the shorter circuit so that the coolant circulates through the longer one: waterpumpcooling jacket thermostat radiator top tank radiator core bottom tank pump.Water pumps have many designs, but most are the centrifugal type. They consist of a rotating fan, or impeller, and seldom are of the positive displacement type that uses gear or plungers. Many water pumps have a springloaded seal to avoid leakage of water around the pump shaft. Some Vtype engines have a pump on each cylinder block.The radiator is a device designed to dissipate the heat which the coolant has absorb from the engine。 it is constructed to hold a large amount of water in tubes or other passages which provide a large area in contact with the atmosphere.The radiator usually mainly consists of the radiator core, radiator bottom tank, and radiator top tank. Radiator cores are of two basic types, the fin and tube type (fins are placed around the tube to increase the area for radiating the heat) and of the ribbon cellular or honey b type. The popular fin and tube type of radiator core has the advantage of fewer soldered joints and is therefore a stronger construction. It consists of a series of parallel tubes extending from the upper to the lower tank. The honeyb type core consists of a large number of narrow water passages made by soldering pairs of thin metal ribbons together along their edges. These tubes are separated by fins of metal ribbon, which help dissipate the heat.The radiator cap serves not only to prevent the coolant from splashing out the filler opening, but also to prevent evaporation of the coolant.The fan is designed to draw cooling air through the radiator core. The fan is usually mounted on an extension of the water pump shaft and is driven by a Vbelt from a pulley mounted on the front end of the crankshaft. Usually the same belt drives the alternator, and belt tension is adjusted by swinging the alternator on its mounting.An aircooling system contains a centrifugal fan, thermostat, fan drive belt, radiator fin, baffle plates, air control ring39。, etc. An aircooling system means that air is used as a cooling agent to circulate through the engine to carry the heat away from the moving parts. When the engine is running, force air is directed over and through the fins to dissipate the heat. In order to regulate the engine temperature by controlling the volume of cooling air, a thermostat is installed inside the metal housing which encloses the engine.The thermostat unit is connected to an air control ring. As the engine bees hotter, the control ring opens wider to admit more air, and closes when the engine is cold. With the ring closed, air circulation is restricted, and a cold engine warms up more rapidly. Rapid warmup is one of the characteristics of aircooled engine, since they do not have heat water in cylinder jackets and radiator.The engine cooling system actually is a temperatureregulation system. For a latemodel engine, the cooling system must maintain a temperature that is high enough for efficient bustion but not so high that the engine will be damaged. The two jobs of the cooling system are to carry excess heat away from the engine and maintain uniform temperature through the engine. These requirements are very critical for an engine with electronic controls that must maintain pr