GM Genuine Parts Heater Water Pumps are designed, engineered, and tested to rigorous standards, and are backed by General Motors. These water pumps are used in some vehicles to pump engine coolant during certain operating conditions. While your engine's main water pump is mechanically driven and stops when the engine does, a heater water pump is electric and able to circulate coolant to the heater core during engine shut off, keeping coolant flowing and the heat going. GM Genuine Parts are the true OE parts installed during the production of or validated by General Motors for GM vehicles. Some GM Genuine Parts may have formerly appeared as ACDelco GM Original Equipment (OE).