Replacing your cambelt – Why is it so important?

Failing to change your cambelt when it’s due could lead to catastrophic engine damage, as you can see by the above picture the belt on the left is so worn that it’s very close to snapping and doing this. The picture on the right shows the replaced cambelt as it should look.

What is a cambelt?

A cambelt is basically a rubber belt with teeth, which synchronises and rotates the crankshaft and camshaft or camshafts. It connects the top half of the engine to the bottom half of the engine and synchronises the valves with the pistons. 

The rubber cambelt / timing belt is located under your bonnet normally at the front or side of your engine and is responsible for keeping various engine components running in time.


What does a cambelt do?

The cambelt / timing belt controls the opening and closing of your engine’s valves to allow gas to pass in and out. Depending on the type of engine you have, it is very important that these valves open in time so that they don’t hit the engine’s pistons.

The cambelt keeps the vehicle’s camshaft and crankshaft turning at the right speeds, relative to each other. The crankshaft moves the pistons up during the engine’s compression and exhaust cycles, while the pistons move down in the power and intake cycles.

In some vehicles, the cambelt may also operate the water pump, oil pump, and injection pump. So, the cambelt or timing belt is critical to your car’s performance.

Overall, a good timing belt will improve the power transmission efficiency and reduce noise.

Overtime the Cambelt will stretch and as a result the engine timing may be effected, resulting in a less efficient engine.


What will happen if I don’t change my cambelt?

If you don’t replace your cambelt / timing belt when it is due for changing, you run the risk of seriously damaging your car’s engine with the valves hitting the pistons. When you consider the thousands of pounds it may cost to replace your car’s engine or repair (and time off the road) it is cheaper to prevent the problem and by replacing your cambelt / timing belt first.

Over time, your car’s cambelt will wear. The more worn a cambelt becomes, the more likely it is to break. Once the cambelt breaks, your car will become undrivable.

The amount of damage a snapped cambelt can cause depends on the type of engine you have. If you have a non-interference engine, you are at minimal risk of serious engine damage. This is because in this type of engine configuration, the pistons and valves do not occupy the same space. If you have an interference engine, a snapped cambelt is likely to cause serious, expensive engine damage due to the valves and pistons hitting each other. A chain-driven engine does not use a timing belt and is not at risk of this damage (but the timing chain can stretch over time causing other problems).

Your cambelt affects some major performance factors within your vehicle, so it’s important to have it checked and replaced when necessary, to ensure safety for you and other drivers, as well as ensuring emissions are as low as they can possibly be.


When should my cambelt be replaced?

Most vehicle manufacturers will advise on either mileage or time, depending which comes first.

During our services we always advise you of the manufacturers recommend replacement interval so you never have to worry.

If you’re not sure when your cambelt is due for replacement we can look this up for you on our autodata system or alternatively it should be written in your owners manual. If you need any further advice or information please do not hesitate to call us on 01803 411920

At TQ1 when changing a cambelt we will always change the waterpump if it is driven by the cambelt and we also replace the  auxiliary belt at the same time as this saves you a lot of money in the long run instead of making separate jobs out of it and paying labour twice when your water pump does need replacing. 

Are there any early warning signs to tell that my cambelt may need replacing?

Often there’s no sign the cambelt’s reached the end of the road as it’s so deeply embedded in the engine.

Trevor Eastman, head of technical services at Haynes' automotive team, says: “If a driver is lucky, they may hear a rattling or slapping noise prior to failure. But in some cases even an expert may not be able to predict a cambelt failure”.

And unlike new brakes or other replacement parts, you may not notice any difference in the way your car drives.

Occasionally some tell-tale signs of a delayed engine include a lack of power and slow pick-up. And in some instances when the engine is idle a rattling noise can be heard coming from the Cambelt area, this is a sign that the belt may have stretched, however the noise disappears when the engine is revved.