What would cause a timing belt to jump?

By Julia Freeman

The timing belt is one of the most important parts of your engine. It is a vital piece of your engine that controls the timing of your camshaft and crankshaft. The belt has to ensure that your valves and pistons move at precisely the right time. A properly running cam belt is vital in keeping your engine running as smoothly as possible.

As with all parts of an engine, the timing belt will deteriorate over time. The belt is made from an incredibly tough reinforced rubber, which will last a long time, possibly up to 7 to 10 years, but not forever. As the rubber deteriorates, the risk of a jumped cam belt increases. Also, the teeth may be stripped from the belt, or in the worst-case scenario, a snapped belt can cause serious damage to the engine.
When cam belts snap or the teeth are stripped, this usually happens as the engine is under strain at elevated speeds. Of course, this is where the most damage is done, as the valves and pistons no longer operate in sync, their point of reference for timing removed, potentially causing damage to the inner workings of your engine.

What can cause the timing belt to begin jumping?

Manufacturers give a recommended replacement interval for the cam belt in the car's service book. This is typically at 60,000 miles or five years. If your timing belt has lasted this long, it could well be time to replace it with another.
In our experience, if the rubber has degraded, your cam belt is at risk of jumping, which means it is definitely time for a replacement, before serious damage is done to the engine.
Apart from general wear and tear due to age, there are other circumstances which can cause timing belts to begin to fail.

Prolonged aggressive driving

Aggressive driving, with persistent high engine speed, can put undue pressure on the timing belt. Also, over-revving the engine with the clutch disengaged, for example before a gear change or before moving off, will cause it to run at a higher rate than it needs to, which can also shorten the life of your cam belt.

Defective belt rollers

If your cam belt is jumping but seems to be in reasonable condition and is not more than 60,000 miles old, there may be an issue with the belt rollers. As with all moving parts, these too will degrade with time, with wear to the bearings or mechanical play within the rollers. Alternatively, the belt tensioner may be failing, meaning it is unable to tighten the belt to compensate for the play in the rollers. This is a common fault in engines due to the strain that they have to handle during normal usage.

Talk to the Protyre professionals

If your timing belt seems to be giving you issues, get in touch with your local Protyre garage, where our qualified mechanics can inspect and service your engine.
In addition to servicing, we offer a range of tyres from manufacturers such as Bridgestone and Sumitomo, as well as mid-range and more pocket friendly budget options.
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About the author

Article Author Photo
By Julia Freeman
Julia is Head of Retail Marketing for Protyre and loves engaging with customers and the business as a whole to make sure Protyre is more than just a local garage.
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