Engine Cooling System Purpose

Your engine is liquid-cooled for a very important reason. As the engine burns fuel, only about one-third of the heat generated is converted to mechanical energy to drive the vehicle forward. Approximately one-third goes directly out of the exhaust system and is wasted to the atmosphere. The final third heats engine internal parts like the cylinder head, pistons, valves, and engine block. The heat absorbed by the engine components must be removed so that internals never reach temperatures high enough to reduce the strength of the materials, aluminum, steel etc. of which they are made. There is a water jacket surrounding the cylinders in the cylinder block and coolant galleries cast into the heads themselves. As coolant is circulated around the cylinders and through the engine block, heat is transferred to the relatively cooler liquid. The liquid is then pumped to the radiator where surrounding air is constantly passed across the radiator coolant tubes. The hotter coolant fluid gives up its heat to the air surrounding the car.  Even during the hottest drives across the desert in the midst of summer, the temperature difference between the coolant inside the radiator at above 200° will still transfer heat to ambient air at 120° temperatures in order to keep the engine at a safe operating temperature.