Water pumps with plastic impellers may not be as reliable as those with metal impellers

The water pump circulates coolant between the engine and the radiator and part of the water pump is an impeller which rotates, thereby circulating the coolant.
You can see the impeller on the above photo – it is on the end of a shaft in the top right hand corner.
Impellers are made either of plastic or metal.

The photo above shows a broken impeller which is made of plastic - it has clearly cracked. Clearly; this is not good.

In our experience, we have found that water pumps with plastic impellers appear to fail more quickly than those made of metal.

This would seem to imply that the benefits of saving weight by using a plastic instead of cast metal impeller could be over-rated……

Therefore, if you are having your timing belt changed and are having the water pump and associated belts changed at the same time, our strong recommendation would be to press your independent specialist to use a German water pump which has a metal impeller.

As Company policy, we ourselves use only German water pumps with metal impellers.