This question is rarely asked. Because in practice, when you entrust your car to your mechanic for the replacement of the timing belt, it will almost systematically “impose” you the joint replacement of the water pump. It’s like that…
A bad habit to unnecessarily inflate the bill? Or on the contrary a necessity and therefore a good idea?
It is necessary to distinguish in reality several cases.
1 / The case of engines where the distribution is chain.
In this case, it is never in the maintenance plan to replace the distribution, which is supposed to last the life of the car. This is not always the case in practice, but that is another debate.
Usually, in this case, the water pump is not driven by the chain, but by the accessory belt. So even if there is a problem with the chain, we will not replace the water pump. And this will only be done in the event of a leak or overheating, which may be due to wear on the internal fins of the pump (but not that, it takes an accurate diagnosis).
2 / The case of timing belt motors which do not drive the water pump.
Same reasoning as before. Replacing the timing system when it expires does not automatically replace the pump, the condition of which should only be monitored (no leaks or wear which would result in a rise in engine temperature).
3 / The case where the water pump is driven by the distribution.
it’s the most frequent case, when the distribution is ensured by a toothed belt. The water pump is then on the “path” of it, and it drives it. And it is in this case that the mechanics recommend the systematic replacement of the water pump at the same time as that of the belt.
You might as well say it right away, It’s a good idea ! For several reasons.
- To begin with, replace the distribution, drop it, make very easy and quick to replace the water pump, which is an inexpensive part. We then “benefit” from the same workforce, and it reduces costs. To put it simply, it is more economical to replace the water pump during the change of distribution, because it only adds a few minutes of MO, rather than replacing the distribution at one point (several hours of MO), and at another the water pump (several hours of MO still). More concretely still: you prefer to pay once € 600, or even once € 500, but then have to pay € 600 again because the pump has failed?
- Another argument in favor of simultaneous replacement: precisely the risk of breakage of the water pump after replacing the distribution. Indeed, by replacing the timing with a new one, this will change the belt tension conditions, generally upwards of course. And the water pump may suffer, at the level of its axis and its bearings, of this increased tension. This will then wear it out more quickly, and cause it to fail. This is of course not systematic, but it is a risk. It is better to start with a new pump.
- Finally, even if the voltage remains the same and does not cause accelerated wear, the water pump remains a part which wears (admittedly slowly) and which will have a hard time surviving a second cast anyway (which is replaced at least every 4/5 years, and at best every 10 years). There is a good chance that it will be at the end of its life or flee when approaching 10 years, and even more so when approaching 20 years. However, replacing it requires you will understand … to file the distribution!
For all these reasons, it is judicious to carry out the replacement of the water pump during that of the distribution, when it is driven by it. In other cases, it is just necessary to monitor the absence of leaks and wear, which would result in overheating.
So this is not a way for mechanics to push you to consume. Phew!
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