When human bodies feel cold, we put on a jacket. Our car engines carry permanent jackets for the opposite reason- - to keep cool! The water jacket is a compilation of passages within the block and head. These passages let the coolant flow around the “hot spots” (valve seats and guides, cylinder walls, even combustion chamber, etc.) in order to cool them off. The engine block is in fact manufactured in one piece with the water jackets cast into the block and also cylinder head.

At normal operation temperature, the water pump forces the coolant during the head gasket openings and on into the water jackets in the tube head. It flows around in there, cooling everything off by fascinating the heat. After doing its thing, the coolant flows through the upper pipe to the radiator where it releases the heat. Then, the water pump sends it back down into the engine’s water jackets to carry on the cooling process. On the sides of the engine are “freeze” or could “expansion” plugs, which are sheet metal plugs pressed into a series to holes in the block. These are planned to hold the pressure of the cooling system, but to pop out if the coolant in the chunk ever freezes.