A water pump is a critical engine component that prevents the engine from overheating by constantly circulating coolant between the engine and radiator. It also pumps coolant through the heater core when heat is needed for the passenger compartment.
Normally, water pumps are out of sight and out of mind. They require no special maintenance or adjustments, and as long as the coolant remains clean the pump should last tens of thousands of miles. Most late-model original equipment water pumps should run well over 100,000 miles before they start to leak or squeak.
Sometimes a water pump will fail prematurely because of corrosion inside the cooling system or because of an imbalance acting on the water pump shaft. On vehicles that still have a mechanical fan mounted on the water pump shaft, a bent blade can create vibrations that may cause the shaft to crack and snap. A bent pulley can do the same thing. Excessive tension on a fan belt or serpentine belt also can overload the water pump shaft bearings and cause the pump to fail. But in most instances, water pumps fail because of shaft leaks.
The unitized seal assembly inside the water pump that surrounds and supports the shaft typically uses a hard ceramic seal to prevent coolant seepage around the shaft. Any abrasive contaminants that circulate with the coolant will scour the seal and eventually cause the seal to fail. The first sign of seal wear or impending seal failure is coolant leaking out the small vent hole on the pump housing or coolant leaking around the shaft. Adding a bottle of cooling system sealer won’t help because the only way to stop this type of leak is to replace the water pump.
Abrasives in the coolant also can erode the impeller inside the pump causing a reduction in the pump’s output (especially with plastic impellers). In some cases, a metal or plastic impeller also may come loose from its shaft, causing a complete loss of pumping action. This will cause the engine to overheat.
A customer has two choices when it comes to purchasing a replacement water pump: new or rebuilt. The trend in recent years has favored new pumps over rebuilt. Why? Because there are no core exchanges required with new pumps, and new pumps are exactly that: brand new with all new internal components and a new housing.
A rebuilt water pump (which many prefer to call a “remanufactured” pump) can be as good as a new pump if the supplier uses top-quality components (seal and bearings), does a thorough job of cleaning, inspecting and reconditioning the old pump’s internals and housing before they are reused and backs their product with a reasonable warranty (a year or longer). But in a price-competitive market, some rebuilt pump suppliers won’t go the extra mile and will cut corners wherever they can to keep the price down. Consequently, the consumer gets what they pay for: a low-priced, low-quality replacement pump that won’t last anywhere near as long as a new pump or original equipment pump.
Considering the amount of time and labor that’s required to change a water pump, buying a cheap replacement pump can be a costly mistake. Any savings that are gained by buying a cheap pump will be more than offset by the time and labor that will be required to replace the pump when it fails again. Do it right the first time and be done with it! Sell your customer a new pump or a quality reman pump from a reputable supplier.
Other items that usually need to be replaced when changing a water pump include fresh coolant, new upper and lower radiator hoses (and clamps) and a new thermostat (highly recommended if the engine overheated). CM