What’s a water pump bearing?

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A water pump bearing supports the impeller shaft and seals coolant inside the pump housing. Signs of damage include squealing sounds and coolant leaks. The bearing is typically a sealed, machined race designed to withstand harsh operating conditions. Most water pumps cannot be rebuilt due to the extreme conditions they operate under.

A water pump bearing is a device used to support the shaft end of the water pump impeller. Fitting tightly around the impeller shaft and firmly in the water pump housing, the water pump bearing is designed to withstand the stresses and load placed on the water pump shaft by the belt drive system engine accessories. In many cases, the water pump bearing is tasked with doing double duty as a bearing for the rotating impeller shaft and a seal to keep coolant from escaping the water pump housing.

The sign of a damaged water pump bearing can present itself in a number of ways. A squealing sound is a common sound from a failing water pump bearing, however, many bearings have been known to fail without making a sound. Often times, you will notice a bad water pump bearing due to coolant leaking out the bottom or back of the water pump. In this case, it’s time for a new water pump or a rebuild of the existing pump. In some circumstances, a water pump rebuild kit is not available, so a new water pump must be installed when the bearing fails in the existing pump.

The style of bearing used in the typical water pump is a sealed bearing. The sealed bearing allows the component to hold coolant inside the engine without leaking around or through the bearing. The bearing is commonly pressed onto the water pump impeller shaft as the fit is extremely tight. The outer surface of the bearing is known as the race. This is commonly machined at a slight angle on a water pump bearing to allow the bearing to better resist leakage.

Manufactured to exacting tolerances, the water pump bearing is designed to operate at extremely high speeds for extended periods of time without failure. The working environment is very harsh for the coolant pump bearing. Operating in a heated liquid, under severe load, and at speeds higher than those to which the typical bearing is exposed, the water pump bearing is subjected to many abject conditions that would destroy an inferior bearing in a very short time. It is because of these extremely harsh operating conditions that most water pumps typically cannot be rebuilt. Many manufacturers are unable to guarantee internal water pump components against DIY rebuild and installation.

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