Coolant Reservoir: Description and Operation

A plastic coolant recovery reservoir is connected to the radiator by a hose. As the vehicle is driven, the engine coolant is heated and expands. The portion of the engine coolant displaced by this expansion flows from the radiator into the reservoir. When the engine is stopped and the engine coolant cools and contracts, the displaced engine coolant is drawn back into the radiator by vacuum. Thus, the radiator is kept filled with engine coolant to the desired level at all times, resulting in increased cooling efficiency.