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Defective Water Pump

A defective water pump can slow or stop the flow of coolant through the engine. The coolant will not be removed from the engine and cooled, forcing the engine to withstand higher temperatures. The coolant needs to be removed from the engine and cooled in the radiator to keep the engine temperature within the optimum range. Failure in the water pump can lead to overheating.

Table of Contents


Temperature Gauge Rises Steadily

The temperature gauge measures engine temperature by measuring the coolant temperature. If the water pump fails to circulate the coolant, the coolant will remain in the engine longer and absorb more heat from the engine. Without a way to dissipate the engine heat, the coolant temperature can quickly rise.

This can be tested by running a car up to a point where the temperature gauge has begun to move. Once it reaches a certain point, turn the engine off. Wait a few minutes and turn on the accessories so the temperature gauge is on, but the engine is not. The temperature will rise quickly, as the coolant has been sitting in the engine. Finally, turn the engine on. If the water pump is operational, the temperature should fall as new, cooler coolant is entering the engine and is being read by the gauge.

If the temperature does not drop, the coolant is not being circulated.

A temperature gauge that is approaching the "danger zone"

Coolant Leaking

A defective water pump may have a leak. If there is a coolant leak, a green or orange liquid will appear beneath the car.


General Wear

Water pumps can wear out under normal driving conditions. They can need replacement before a car reaches 100,000 miles.

Loose or Detached Belt

The water pump is driven by a belt attached to the engine. If this belt is detached or loose, the water pump will not operate effectively.

See Also

Thermostat Stuck Closed

A problem that exhibits similar symptoms is the thermostat is stuck closed. The thermostat "traps" the coolant in the engine, preventing from circulating to the radiator. This will cause the engine to overheat in a similar manner to a defective water pump.

This article was last edited on September 20th, 2010 at 5:53 PM
Category: Cooling