Water Pump

A bad water pump may leak coolant, fail to circulate coolant, or it may produce a grinding sound. Rust in the cooling system or lack of antifreeze is the most common causes for pump failure. These conditions can accelerate seal, shaft, and bearing wear. An over-tightened fan belt will also cause water pump failure.

To check for a worn water pump seal, pressure test the system and watch for coolant leakage. Coolant will leak out of the small drain hole at the bottom of the pump or at the end of the pump shaft.

Worn water pump bearings are checked by wiggling the fan or pump pulley up and down. If the pump shaft is loose in its housing, the pump bearings are badly worn. A stethoscope can also be used to listen for worn, noisy water pump bearings.

Water pump action can be checked with a warm engine. Squeeze the top radiator hose while someone starts the engine. You should feel a pressure surge (hose swelling) if the pump is working. If not, pump shaft or impeller problems are indicated. You can also watch for coolant circulation in the radiator with the engine at operating temperature.

Whether a defective pump is replaced or rebuilt depends on parts supply and cost. A water pump rebuild involves disassembly, cleaning, part inspection, worn part replacement, and reassembly. Few mechanics rebuild water pumps because rebuilding takes too much time and is not cost effective.

The removal and installation of the water pump varies with different vehicles. Therefore, the applicable shop manual must be consulted for the step-by-step procedures.

When you replace a pump, install a new gasket. Make sure the mating surfaces are clean and smooth. The application of a gasket sealer to both sides of the gasket is recommended. Then after refilling the cooling system, the pump should be checked for leaks, noise, and proper operation.