Water pumps – why do they break?

At the beginning of the puzzle: which device mounted in the car can boast of pumping nearly half a million liters of fluid in just one year? The answer is simple – it is of course a well-known coolant pump, commonly known as a water pump. However, despite achieving great results, it is also exposed to various types of damage. Prophylactically, it should be replaced after about 100,000 km.

water pump audi

Watch out for assembly errors!

As experts argue, the incorrect operation of water pumps does not result in the vast majority of cases from technical failures of the latter, but from … mistakes made during assembly. The most common sin is allowing the pump to run “dry” (including to check that the water pump impeller is moving freely), as well as the use of improper gaskets and sealants. Further on, flooding the cooling system with the wrong or contaminated fluid and – unfortunately, this is often the practice – assembling worn or partially damaged parts. It is therefore worth following strict procedures to avoid potential failure of the water pump immediately after installation.

Just not dry!

As has already been said, the pump must not be checked for dry running. Why is this so important? Its shaft seal must be constantly lubricated and therefore the pump must not run without coolant. Even a short, test run of the pump without the latter can lead to permanent damage to the internal seal of the pump and, as a consequence, cause coolant leakage during normal operation. So how do you check the water pump properly? First of all, the coolant level in the entire system should be topped up and the pump pulley should be turned several times before starting the engine. Thanks to this operation, the coolant will lubricate the pump seal, thus avoiding permanent damage.

Bad seals or contaminated coolant

It will sound like a truism, but not all workshop professionals take this simple rule to heart: each time the water pump is replaced, old gaskets and seals must be replaced with new ones! Attention! If the new pump is fitted with a gasket at the factory, then no additional seals may be used. The reason for this recommendation is prosaic: additional sealing may cause problems with proper seating of the pump, and in extreme cases damage to the factory seal. Premature failure of the water pump can also be caused by using the wrong or dirty coolant. The use of the former will result in inadequate corrosion protection of individual cooling system components. In turn, the contaminated coolant will quickly damage both the sealing of the water pump and its individual components. The consequence of this will be quick leaks and the need to replace the pump again. Before installing a new water pump, it is also recommended to flush the entire cooling system with a special device.

New pump – old belt?

Never! This is the only correct answer to this question – also in the opposite version, i.e. the old pump – a new belt! Such a system, regardless of its configuration, carries a risk (bordering on certainty) that the entire cooling system will fail prematurely. Experts therefore recommend a comprehensive and simultaneous belt replacement with tensioners when installing a new water pump. At the same time, the manufacturer’s detailed recommendations should be followed, especially when it comes to tightening all fastening screws with the correct torque. After installing the water pump, do not worry too much about small leaks from the so-called drainage hole of the latter, as they are the most normal phenomenon during the running-in period of pump seals.

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