The purpose of the cooling sysstem is to keep the engine at its most efficient operating temper-ature at all speeds under all driving conditions. As fuel is burned in the engine, about one-third of the heat energy in the fuel is converted into power. Another third goes out through the exhaustpipe unused,and the remaining third must be handled by the cooling system. This means that theengine can work effectively only when the heat energy is equally handied so as tokeep the enginetemperature in balance.