[Tannaton]

At the risk of siding with Clan on this one and once again being branded the "usual suspects...."

Think of it like this (I've made the figures up but I don't think they're fanciful):

First cambelt change - risk of water pump failing before next cambelt change:

Retain original pump: 0.02%
Replace pump with genuine Volvo: 0.01%
Replace pump with quality aftermarket: 0.1%
Replace pump with cheap part : 1%+

Second cambelt change - risk of water pump failing before 3rd:

Retain original pump: 0.04%
Replace pump with genuine Volvo: 0.01%
Replace pump with quality aftermarket: 0.1%
Replace pump with cheap part : 1%+

I would say, if you are of the opinion that you want to reduce the risk of a pump failure, however small that maybe, the replace it - but only with a genuine one. This doesn't factor in the risk of "disturbance" - i.e. the new pump not fitted well and leaks from day 1 from the gasket line...

By quality aftermarket - I would say only 3-4 manufacturers fit this like SKF - not "First Line" etc. They key point is if you remove your genuine, factory pump and replace it with something that cost £25 on e-bay you are likely in the region if 50-100 times plus more likely for it to fail in the next cycle than if you left the original. I've thought about that carefully and I think it's fair to say it.