Unlikely to be a bad failing waterpump

Don’t replace the water pump just yet!


How often do cars for sale just need a new water pump? In my opinion, too often. The mysterious device that pumps water is seen as the culprit to all cooling troubles. A bad failing waterpump is characterized as leaky, noisy, seized and it is an issue, however, it is relatively rare.

Unlike most pumps, the coolant pump is simple with very few failure points. It’s easy to imagine that the impeller wore off, however, in most cases, it hasn’t. Let me put its purpose in perspective.

The role of the cooling system is to remove heat from the engine. Coolant absorbs radiated combustion heat and then carries it to the radiator. Then the large surface area of the radiator dissipates the heat into the surroundings.

The water pump is responsible for the movement of coolant in the system. The engineers designed the cooling system such that the amount of heat created by the engine could be transferred to the radiator. But keeping the engine temperature under control is a complex balance.

The water pump in most vehicles is linked to the engine speed. It will pump larger volumes when the engine is spinning fast. However, the amount of heat produced by an engine is not related to its speed. The engine load is far more indicative of heat production. For example, heavy acceleration, towing, and uphill driving will produce more heat than revving the engine standing still.

Another important factor is the time component. The rate at which heat is produced versus shed results in the current temperature. Heat production can happen on demand, however, shedding heat is much slower. This is most noticeable when coming to a stop after highway driving. There is a slight temperature increase and it takes time for the engine to cool off.

Heat Equation


Heat production is one side of the equation. Dissipating the heat is the other side. Adequate airflow past the radiator is an important factor. Which is why the fan is a crucial component. Cooling off the coolant in effect recharges it for another round of heat transfer. The lower its temperature, the more heat it can absorb. Our fan controllers allow the fan to turn on at a lower temperature thereby improving the airflow.

I feel these insights should help with diagnosing overheating. Identifying if the problem is from excessive heat production, or inadequate dissipation is the first step. On the topic of water pump, to rule it out completely, it’s possible to remove the upper radiator hose for a moment. Try to contain the mess, but the fountain should be a clear indication that coolant is indeed circulating.

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