How to know when to change a timing belt

when to change a timing belt

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How do you know when to change a timing belt? Our guide outlines the main mileage intervals for timing belt changes and why it’s important.

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Most drivers know exactly how important the engine is as a component in every car, but few drivers know what the timing belt actually does and how often the timing belt should be changed. A properly tensioned toothed belt is one of the most important requirements for a smooth engine run. 

Should the timing belt tear, this can cause numerous engine damage. Most of the time it is the drivers themselves who cause this damage because they simply have the timing belt replaced too late. 

When to change a timing belt

In contrast to other car components – such as the brakes – it is difficult to estimate the remaining mileage of a timing belt and when the next timing belt change should take place. Most timing belts have to be changed every 62,000 to 75,000 miles (100,000 to 120,000 km) at the latest. However, some newer models also last up to around 104,000 miles (200,000 km). Most manufacturers specify a specific time interval for changing the timing belt, as the rubber of the belt becomes more and more susceptible to damage after a few years and can then tear.

What does a timing belt actually do?

The toothed belt is part of the engine and is jointly responsible for the combustion process in the engine control. It connects the two camshafts with the crankshaft. The pistons set the crankshaft in a rotary motion while the camshafts control the valves of the engine. 

A basic requirement for the function of the motor is that the valves are controlled exactly. The toothed belt is therefore a central element of the engine management system and can lead to serious damage to the engine if it is changed too late.

Therefore, you should always rely on the advice of a professional. If the timing belt is already very porous or has the first cracks, you should have it changed regardless of age and mileage. 

Most manufacturers give a time interval for the change, as the rubber of the belt becomes more and more prone to damage after a few years. It is advisable to use this time interval for changing the toothed belt as a rough guide, but of course the intervals also vary depending on the mileage, the idle times and the outside temperatures.

What happens if the belt breaks?

Unfortunately, with a toothed belt it is not the case that it gradually stops working. Regardless of whether the toothed belt breaks completely, slips or “only” a few teeth are missing – the consequences are the same, because it always ends in engine damage. 

If the toothed belt is no longer functional, the valves will hit the piston. As a result, the car no longer drives and an expensive repair is due to get the car moving again. The belt must be replaced in order for the engine to work again. It can also damage many other parts of the engine.

What is included when changing?

A timing belt change is generally an expensive repair, as it is associated with a lot of work on all cars. First the toothed belt guard must be removed so that the trained mechanic can change the toothed belt. This is usually only possible by dismantling the front of the car. As soon as the toothed belt is exposed, the old belt can be removed and new ones installed accordingly.

Normally the tension and deflection pulleys are also replaced when changing the timing belt. These have the task of guiding and deflecting the belt and keeping it tensioned throughout its entire service life. Since the water pump is also driven by the toothed belt, this is also often replaced. 

All new parts are then professionally installed according to the manufacturer’s specifications, whereby the mechanic must pay particular attention to the position of the crankshaft and camshaft. When the new parts are installed and properly seated, the timing belt is perfectly tensioned and the cladding is reinstalled.

In order to avoid problems with the timing belt, it is very important not to exceed the timing of the timing belt change and to observe it. So we recommend that you have a mechanic look after the timing belt if your car is going to the workshop anyway.

What is the difference between a timing belt and a timing chain?

The timing belt and timing chain are used to drive the camshafts and the crankshaft. The timing chain is made of steel and usually lasts the length of the engine’s entire life. Therefore a timing chain does not normally require any maintenance. 

A timing belt is typically rubber with high-tensile fibres (e.g. fiberglass or Twaron/Kevlar) running the length of the belt as tension members. The toothed belt is toothed on one side, which means that it should run smoothly on the drive and driven gears. Due to its material, the toothed belt must be changed regularly, as the material becomes brittle and can sometimes crack.