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Why Do Mechanics Replace The Water-Pump If I Ask For A Timing Belt

We've all had these discussions before. The car goes into a mechanic for a single part (say a timing belt) and when the invoice comes out they've replaced the water pump, fan belts, engine mounts, fuel pump and half the interior all at the same time.

So why is it that so many mechanics want to replace the disc/rotors when doing brakes or replace the water pump with the timing belt? Is it just another way for the mechanic to make sure they get as much money as possible or is there a world where this all makes sense?

This is kind of a hard discussion for us to have as mechanics (and one that we have fairly regularly too). It also makes total sense why it’s a pain point for so many vehicle owners as well.

Cars are fairly complicated bits of machinery that are constructed in a way to make sure all of the components work together with as few unnecessary bits as needed. These individual components are put together in a factory to form bigger assemblies and then fitted to the vehicle in a particular order that allows as much to be packed in as possible.

The engine might make up one assembly, as will each corners hub and suspension, the fuel pump and filter and even the dash as they are all an accumulation of multiple other parts.

This means that much like an onion, there’s often multiple layers of components needed to be removed to get to the core thing that needs replacing.

This is the main reason a mechanic will be replacing additional parts in the course of a repair. If six layers of parts need to be removed to replace an item, mechanics will often look at other common failure points and try to replace them at the same time.

Even though this may be more expensive at the time, this reduces the overall labour cost of replacing both components and also drastically reduces the likelihood of that core component failing between the next replacement interval.

For example, when replacing a timing belt, most mechanics will also opt to replace the tensioner and idler pulleys at the same time. This is a particularly good idea when replacing the timing belt as they are one of the key things keeping an engine running and even though the old pulleys may be in fair condition at the service, if they fail between now and the next timing belt replacement they can cause a lot of damage.

In addition to the timing belt and pulleys, almost all mechanics will choose to replace the fan belt and water pump at the same time. The water pump is a particularly important part of this as to replace the water pump the entire timing belt assembly would have to be removed again meaning essentially double the labour.

Simply put, mechanics are usually looking to replace these additional parts to prevent headaches down the road instead of looking for another way to make money.


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