A plastic coolant recovery reservoir connects to the radiator with a hose. During vehicle use, the engine coolant heats 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 coolant cools and contracts, vacuum draws the coolant back into the radiator. This results in increased cooling efficiency because the radiator is kept filled with the desired level of coolant at all times.