The radiator is a device designed to dissipate the heat which the coolant has absorbed from the engine. It is constructed to hold a large amount of water in tubes or passages which provide a large area in contact with the atmosphere.

At normal operating temperature, the water pump forces the coolant through the head gasket openings and on into the water jackets in the cylinder head. It flows around in there, cooling everything off by absorbing the heat. After doing its thing, the coolant flows through the upper hose to the radiator where it releases the heat. Then, the water pump sends it back down into the engine's water jackets to continue the cooling process.