Water pump for your car

Your Water pump worn out? » Read more about common malfunctions • Repair • Replacement manual

The water pump is the central part of the engine's cooling cycle, responsible for the coolant circulation and ensuring that the engine does not overheat. A water pump failure has fatal consequences. Generally it announces a defect long on beforehand. In addition to the pumping function, the water pump has an additional task: the tensioning of a timing belt or V-belt.

The coolant pump is located right beside the engine and in constant operation. It is driven by a belt or a gear wheel. The coolant pump builds pressure necessary to press the coolant through the engine. The coolant enters the water pump in a cold state. The pump leads the coolant through the engine block by coolant hoses. These hoses conduct the water through the radiator, situated in the front of the car. To enable pressure compensation at variable engine or external temperature, many cars are equipped with an expansion tank. This enables checking and, if necessary, adding coolant. In cars without expansion tank, cooling water is added in the radiator.

Technically, a water pump is a very simple component, consisting of a housing with a shaft running through it. At the end of the shaft sits a wheel, driven by an external belt drive. The shaft has an internal blade wheel, setting the water in motion. The pump's weak point is its gasket, sealing the pomp from the exterior as well as its shaft and its bearing. In order not to compromise its tightness, the shaft is often only equipped with permanent lubrication or mounted with a sealing gasket. No traditional ball bearings are used for a water pump as these cannot be properly sealed. The one-sided pressure by the belt causes wear to the bearing's extremities. The typical symptoms of a defective water pump are:

- A loud squeaking of the pump - Leakage of the housing

Replacement of a water pump is not very complicated. If the coolant pump is additionally used as a tensioning element for the timing belt, both components are generally replaced simultaneously on occasion of their regular maintenance. Conversely, it makes sense to replace the belt, when the water pump needs replacement. In many cars, like e.g. the old Opel Corsa A, the water pump is mounted onto the engine with three bolts. After loosening them, the pump can be replaced by a new part.

Engine manufacturers constructed the coolant pump as a wear part. Sooner or later its replacement is due. Manufacturers guarantee the continuous functioning of the engine, even if the used water contains a lot of calcium. In systems where the coolant pump is used as a belt tensioner, it is generally part of a replacement set. Coolant pumps driven by a belt disc are easier to replace. In these systems there is no need to consider the sensitive timing belt with its timing control. In both cases, prices for a new pump start at ca. 30 euro (£26). The most recent generation of water pumps includes variable pumps with their own electric motor. These promise a considerably longer life span than the traditional water pumps. Manufacturers mention a 6-fold increase in life span, which however still needs to be proven. The electronic and variable water pumps have several other benefits: they can be better installed in the engine block and are able to offer adjustable pumping performance. The elective drive and adjustment make the electronic water pumps very expensive.