Water cooling In water cooling system, the cooling medium used is water. In this, the engine cylinders are surrounded by water jackets through which the cooling water flows. Heat flows from the cylinder walls into water which goes to the radiator where it loses its heat to the air. Usually some antifreeze is added to the cooling water, due to which it is often referred to as coolant. Both these terms have been used in this chapter, often meaning same unless the context requires otherwise. Water cooling systems are of two types 1 Thermosyphon system 2 Pump circulation system Advantages 1 As the circulation of coolant is maintained by natural convention only, the cooling is rather slow. Therefore, to have adequate cooling, the capacity of the system has to be large. 2 Due to the quantity of coolant being large, it takes, more time for the engine to reach the operating temperature. 3 Radiator header tank must be located higher than the top of the cylinder coolant jackets, which is no more possible with the modern body styles. 4 Certain minimum level of coolant water must be maintained in the system. If the coolant falls below that level, continuity of flow would break and the system would consequently fail.