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Forgive my ignorance but I'm sure I have read here or in HJ's column that when the wife's 1.8 Astra has its upcoming timing belt change (at 40 000 miles) it is advisable to also change the water pump at the same time. Could someone tell me why that is and is it going to cost me a shedful of cash?
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The water pump is driven by the cambelt. When eventually the water pump bearing starts to fail, it'll cause the cambelt to fail with it's usual effect - major rebuilt. If you only replaced the water pump every other cambelt you'd be expecting 80k which is probably about average. That means in betting terms a 50:50 chance of ££££ failure.
The water pump isn't expensive, under £26 for a discounted GM part from AutoVaux, and the labour is negligible as all the work has been done to strip down for the cambelt.
Changing the water pump has the same logic as changing the tensioner & rollers at the same time as a cambelt - they don't cost much extra to do but have the same £££££ effect if they fail.
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>>but have the same £££££ effect if they fail.
Yes, this is especially true for the 16v engines, not such a problem with 8v - although if the belt drive fails, you still break down!
Since Vauxhall changed to using automatic spring tensioners, and you don't need to disturb the water pump to fit a new belt, I don't bother fitting a new water pump every time. But, the water pump isn't an expensive part, and it isn't a large amount of extra labour once the engine's front end has been stripped down for the cam belt change, so it probably gives peace of mind to change it - especially on 16v engines.
Number_Cruncher
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The water pump is driven by the cam belt. To replace the water pump the timing belt (and tensioners) will need to be reomved and replaced with new.
If you fit a new belt to an old pump it will have a different tension on it that it did before (no matter who does the job and what equipment is or isnt used) and that tension is likely to affect the inner seal of the pump which will over time (short or long ) affect the pump and likely cause it to fail.
if it does fail the timing belt as explained above will need to be changed again so you will ed up paying for the job twice. The cost of a pump at the same time as a belt change is minimal. far better economic sense to have it done at same time.
Also, if the pump was to fail in service, it is highly likely it will cause the belt to fail, unless caught very early, and could result in catastrophic engine failure!
The pumps are a known weak item on these engines too.
Hope this helps, please ask for more if anything not clear etc !
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Thanks very much gentlemen. I would have had the water pump done anyway because of what I remember reading but am sure as damn it will do after your advice. The car's been faultless so far so I'm sure it will all pay off in the long term.
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