The engine produces power by converting chemical energy of the fuel into heat energy by combustion. Part of the total heat produced by combustion is used to push the piston downward and thereby producing necessary power . Some of the heat is carried away by the exhaust gases through the exhaust valve. The remaining heat is absorbed by the engine itself which increases its temperature . The heat of the engine is absorbed by the coolant in order to bring the engine temperature within its normal range. A typical automotive engine cooling system consist of a radiator , fan, water pump, coolant reservoir ,thermostat, heater core and necessary plumbing for both the radiator and heater core. When the engine is started, the water pump connected to it also begins to pump the coolant around the engine cylinder from the lower radiator tank into the coolant passages . The flow of the coolant is from the lower tank to the engine block, then to the cylinder head and finally towards the outlet for the radiator .The coolant begins to absorb the heat produced by the combustion process and flows towards the radiator inlet . However the thermostat restricts the coolant to flow towards the radiator until the temperature of the coolant is not raised above the engine operating temperature which is usually 200 -250 degree Celsius . At this instance ,if the heater inside the cabin is turned on, the coolant is made to flow through the heater core via the bypass hose . The heater core is a mini radiator, which is used as heat exchanger to transfer the heat from coolant to the air that flows inside the passenger compartment. The thermostat on the other end acts as a regulating valve to control the coolant flow into the radiator and maintain the engine temperature within optimum range . When the coolant passing through the thermostat is at higher temperature usually 180 F the wax begins to melt .The melting causes thermal expansion of the wax which in turn pushes the rod and thereby allowing the coolant to flow outside . Fan is actuated by thermostatic switch once the coolant flows outside the thermostat.  The coolant past the thermostat value enters into radiator upper tank through the upper radiator hose .Due to high temperature of the coolant there are chances of building up of high pressure that might block the coolant from entering into the upper tank . To avoid this the upper tank is provided with a pressure regulating valve ,which opens when the pressure in the system increases beyond the recommended value . The opening of the valve allows the high pressurized coolant to flow into the coolant overflow tank. While flowing downwards the coolant loses its heat to the air flowing past the space between the flat tubes . The fan increases the draught of air and thereby increases the heat transfer rate . For better cooling effect the heat transfer area is further increased by providing fins on a flat tube .When the coolant reaches the lower tank of the radiator , the temperature of the coolant reduces considerably .This cold coolant is circulated back around the engine cylinder and the cycle is repeated . Now we know how the cooling system of car operates .At cosmo car parts we provide you high quality water pump , radiator ,engine water pump gasket and timing belt at the best price available for you .