The auto water pump is the heart of the auto cooling system. Belt driven by the crankshaft, it circulates the coolant through the engine block and radiator. The auto water pump is located between the radiator and the front of the block, and consists of an Impeller, shaft and bearing, fan pulley hub, and seals. The impeller, mounted on the shaft, has curved vanes or blades; when turned, they throw the coolant outward by centrifugal force. This pushes the coolant through the pump outlet and into the cylinder block.
Seal failure is the most common malfunction in auto water pumps. Seal failure makes itself known when coolant trickles down from the pump’s bleed hole, which is located on the underside of the pump housing. Inspecting the bleed hole might require using a small mirror or getting underneath the car. The bleed hole is important because it allows coolant to run out of the engine before it can contaminate the shaft bearings.