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Timing belts – what happens when they break?

Timing belts – what happens when they break?

Your car’s timing belt is a seemingly innocuous part thanks to its low value and apparently simple job within the engine. After all, all it has to do is go around and around. So why then, does it cost a small fortune when one breaks?

What does a timing belt do? 

The job of a timing belt is to, frankly, the keep the engine timed. Within the walls of your engine you’ll find a delicate and perfectly choreographed ballet of metal and oil.

Con rods rise and fall, cranks spin, valves open and shut, pumps keep everything oiled and all of this, every bit of it, is overseen by the motion of a £30 bit of rubber.

Or in some cases, a chain. But as chains seldom, they have no place here. 

The timing belt makes sure valves open when the cam or cams are at the right point in relation the position of the crank and consequently the pistons, which when timed to perfection can happily house spark, ignition and combustion, which translates to us a forward motion. 

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What does a timing belt do?

What happens when a timing belt fails? 

Given its long list of responsibilities, there are no prizes for guess that timing belt failure is pretty catastrophic. It’s possible to ‘get away’ with it if your car has what’s known as a non-interference engine, by which we mean the innards don’t clatter into each other without a belt.

Sadly though, most modern powerplants are engineered so finely, and to such small tolerances that without a belt, things go very wrong, very fast. The valves will crash into the pistons, which will be moving, so they’ll crush and bend the valves if the valves don’t punch through the piston cap.

This ins turn can result in metal being broken off, which will damage the cylinder walls and also the combustion cap within the cylinder head.

If you’re really unlucky, small fragments of metal could be pulled through to the exhaust, and if you’ve got a turbo, it could chew up said metal and grade the blower, too. Basically, if a timing belt snaps, it’s bad, bad news. 

Is that the end of the car then?

Honestly? Probably. If a timing belt snaps, the chances are it’s going to do a lot of damage. There are rare exceptions where the horror within has been minimal, but honestly, if it happens, prepare for the worst. 

What happens when a timing belt fails?

Can a timing belt be fixed? 

Of course. Anything can be fixed, and a snapped timing belt is no different. Mainly because a belt is a few quid. It’s everything else that will hurt your wallet.

You’ll have to have the engine dismantled, inspected, any part replaced, engine rebuilt then you’ll be good to go. Though all that is going to be upwards of four figures.

The number will go higher the more modern/complicated your engine is. 

Can a timing belt be fixed?

How do I stop it happening? 

Regular maintenance carried out to the manufacturer’s specifications. Remember, the interval is X years AND X miles, not X years OR X miles.

So, if your car has only done 10k, but it’s four years old, you need to change the belt. They get old and brittle, which is what causes them to snap.

Check your timing belt, have a close look at it and look for cracks, wear or fraying of the fibres that form its construction. And take no chances, don’t put it off.

On an older car a snapped belt is a write off.