Water Pump Weep Hole

The water pump weep hole is a small, intentional opening cast into the housing of an automotive water pump. It is located between the pump's internal coolant seal and the outer bearing. Its primary purpose is to act as a diagnostic window and safety release, allowing coolant that leaks past the primary shaft seal to escape the pump housing rather than entering and destroying the shaft bearing.

Under normal conditions, a tiny amount of moisture may occasionally weep from the hole and evaporate, leaving a faint crusty residue. However, if the water pump's internal seal fails, coolant will leak steadily from the weep hole. If this leak goes unnoticed, the cooling system will lose pressure, the engine will lose coolant, and the water pump shaft bearing will wash out, leading to noisy operation and eventual pump seizure.

Symptoms of a failing water pump seal include a green, pink, or orange crusty buildup around the weep hole, active coolant dripping from the pump area, a low coolant light, and engine overheating. Diagnosing the leak involves pressure testing the cooling system and inspecting the water pump with a mirror. If coolant is actively leaking from the weep hole, the water pump must be replaced.