Car water pump

How to determine the auxiliary water pump failure

Diagnosis of the component begins with its inspection. Fluid stains on the part surface indicate that integrity of the housing or the seal is impaired.

Then start the engine, switch the heater on to the maximum temperature and listen if the pump started operating. If it does not switch on, use a multimeter or a test bulb to check whether the power cable is serviceable.

The pump must be disassembled for a more comprehensive examination. Corrosion of metal components indicates that the part requires replacement.

You may identify that an auxiliary water pump has to be inspected, by the following symptoms:

• the auxiliary heater turns off prematurely;
• the engine does not warm up well at idle speed (relevant for diesel power units);
• too low temperature in the passenger compartment when the heater is on;
• the on-board computer signals an error;
• frequent overheating of the engine;
• the coolant level has decreased.

Causes of the auxiliary water pump failure

The most common pump failure is wear of the electric motor contact brushes. Eventually they wear out, and when the power is supplied the motor of the component does not activate. Typically, the need to replace the brushes arises after 100,000 operational kilometers.

The part’s exposure to moisture and dirt may lead to corrosion of the housing and oxidation of contacts. Besides, the pump shaft may rust in the case of a prolonged vehicle non-use. The shaft jamming can also result from the ingress of a foreign object between the impeller blades.

The coolant leakage from the drain hole or from the pump mounting seat is usually a result of the end seal wear. Premature seal destruction can occur due to usage of a contaminated fluid or the pump turning on with a lack of it. Usage of an unsuitable fluid or mixing of fluids different in composition are also hazardous for the unit components. Besides, neglecting the antifreeze replacement intervals may lead to clogging of the pump lines.

If the component continuously operates under high stress, the risk of turn-to-turn short circuit in its winding is considerably higher.

Repair and replacement of the auxiliary water pump

Generally, the repair of the auxiliary coolant recirculation pump is not expedient, but in some cases the problem can be solved by replacing the brushes or cleaning the parts.

The part removing and installing procedures usually do not involve any difficulties. Before starting the replacement, you need to drain the fluid from the cooling system. Then, loosen the clamps, remove the hoses from the pump connectors, and pull out the wire harness connector. You need to clean the pump mounting seat from dirt and corrosion, and then install a new pump after replacing the seal. After that, you can reconnect the hoses and the wire harness connector to it, and also refill the antifreeze in the cooling system.

To check the part serviceability, start the engine, warm it up, and then switch on the auxiliary pump. If the component is operable and correctly connected, you will hear a characteristic buzzing noise.