Heat is produced in the engine cylinders during combustion of the fuel and air causing high cylinder temperatures. The cooling system removes heat from the engine quickly and continuously to prevent overheating which would cause a reduction in engine performance and, in extreme cases, seizure and damage to the engine components.

Water cooling system

Liquid cooling system are normally used for heavy vehicle engines. The coolants absorbs heat from the engine and is circulated to the radiator which transfers the heat to the cool air passing through it.

Thermo-syphon system

In this simple system, which is seldom used with modern engines, circulation of the coolant depends upon the difference in density between the hot water in the jacket and the cooler water in the radiator which produces convention currents. The coolant passages must be free from the obstructions and restrictions, the connecting pipes and hoses between the engine and radiator should have a large diameter, and the radiator, for effective circulation of the coolant.

Successful operation of this system also depends upon the coolant level of the delivery pipe to the radiator header tank. A wide temperature difference between the coolant in the jacket and the coolant in the radiator is also necessary for effective circulation. This system requires a high and large radiator and a large quantity of water when compared with a pump system. Cab system and coach work designs do not usually permit a high radiator, making this system impracticable for most modern vehicles.

Also check: Air Cooling System In Engine

Most of the above disadvantages are overcome by employing a pump to assist circulation of the coolant, although the Thermo-syphon system is regarded as less costly to maintain and is more reliable due to its simplicity.