Water Pump

The Water Pump is an vital component of the cooling system. It causes coolant to circulate throughout the cooling system.

Function

The water pump is mounted to the front of the engine block. Its pulley holds the cooling fan and fan clutch and is driven by drive belt. As it rotates, its impeller spins to pull coolant through the thermostat housing and into the engine block, where is is then circulated through the block, heads, heater core, and other cooling system components.

Failures

The water pump is a durable component, and while it should be replaced every 60,000 miles as part of maintenance, it is not impossible for it to fail at other times from other causes. Non-Nissan water pumps, for example, are especially notorious for premature failure.
Some of the ways the water pump can fail are...

• Worn bearings, causing play in the shaft and leakage.
• Worn seals, causing leakage (seen through a weep hole on the water pump housing).
• Broken housing, caused by over-tightening of its drive belt.
• Eroded impeller blades, caused by the use of tap water through the cooling system, or extended periods of inactivity.

A water pump which sat long enough for the impeller blades to erode (right) compared to a good water pump (left).

Replacement

The water pump should be replaced as part of the 60,000 or 120,000 mile maintenance procedure. For more information, see the Timing Belt Service article.