What Happens When Your Cambelt Is Replaced?
FixMyCar explains what happens when your cambelt is replaced.
Book a cambelt replacement nowEllie Dyer-Brown
Wednesday March 27 2024
6 min read
The cambelt - also known as the timing belt - is an important component in your car's engine. However, many drivers are in the dark about what it is, how it works, and what happens when it's replaced. This guide is designed to answer all those questions and more.
What is a cambelt?
The role of a cambelt is to control the timing of your car's internal combustion engine - it sends rotational force from the crankshaft to the camshaft to determine when the valves to cylinders open and close. These valves let fuel and air in and out. As the camshaft turns, lobes push on the valve mechanisms, forcing them open or releasing them.
This process must happen at precisely the right time for the engine to run correctly. Some cars have twin camshafts - one controls the inlet valves and the other controls the exhaust valves - but these still rely on the movement of a cambelt or timing chain.
What does a cambelt look like?
Cambelts are usually made from specially treated materials like neoprene, rubber, and polyurethane. They look like long belts with teeth that allow them to grip the gear at the end of the camshaft.
Where is the cambelt on a car?
Cambelts are usually located outside the engine, while timing chains are found in the engine, lubricated by oil. Recently, some manufacturers have started using wet belts, which run internally in engine oil, like timing chains. The best way to determine whether your car has a cambelt and where to find it is to look in the owner's manual.
When should a cambelt be changed?
Cambelts typically last between 40,000 and 100,000 miles. For cars with lower mileage, the recommended replacement interval is every five or six years. Your car’s manual may also recommend cambelt replacement intervals.
The most common time when a faulty cambelt is identified is during your annual MOT. Replacing it can be costly as it involves a lot of labour.
Signs of cambelt failure
Common signs of cambelt failure include:
Rough idling
Why do cambelts need to be changed?
As cambelts age, the rubber they are made from starts to perish and weaken, eventually causing them to snap. When this happens, the best-case scenario is that the engine cuts out. The worst-case scenario is that the valves collide with the pistons, potentially destroying the engine.
You don't want to risk wrecking your engine, so paying attention to replacement intervals is important. Otherwise, you could end up with a repair bill that stretches into thousands of pounds, and you might even have to replace the whole engine.
Another problem that can happen as the cambelt ages is that the teeth can wear down and start to slip, changing their position. This is called 'jumping a tooth', and there are a couple of possible outcomes. Either the timing of your engine will be slightly off, or the valves and pistons will collide, causing severe damage.
Cars with 'interference engines' are particularly at risk of damage from cambelt failure because when the valves are open, they occupy the same space as the pistons. They are only supposed to open when the pistons aren't in the way. However, if the timing is wrong or the cambelt fails, the synchronisation process won't work, leading to the valves meeting the pistons at a high speed.
The image above shows a piston repair job in progress.
What happens when your cambelt is replaced?
The location of your cambelt varies depending on your car's make and model. How easy the part is to access will also affect the cost and labour time. Each car is slightly different, so the information below is a rough guide only.
First, the fan belt is removed by loosening the nuts and pushing the alternator down.
The bolts are unfastened from the cambelt covers, and they are taken off.
After unscrewing the bottom cover, the cambelt should be visible.
The mechanic will typically mark the cogs at this point to remember where they line up for piecing it back together at the end.
The bolt on the tensioner pulley is loosened. The mechanic presses down on it, which causes the belt to come off.
The next step of the process is to put the new belt on.
The new belt is slipped over the cogs and loosened on the tensioner pulley, tightening the new cambelt.
A wrench is then used to ensure the bolts are tight enough to keep the tensioner in place.
The final stage is to put everything back together again in reverse order.
The process of replacing a cambelt isn't straightforward, and if the job isn't done correctly, it could result in engine damage. For these reasons, we'd recommend having it done by a professional.
Frequently asked questions
How can I tell if a car has had its cambelt changed?
The first thing to do is check a vehicle's service booklet. However, even if you see a note saying 'cambelt changed', you still shouldn't take it as a given unless there is an invoice or receipt proving the work was done.
You can take it a step further by contacting the garage that supposedly carried out the work and asking them to confirm whether the cambelt was replaced. If you're in the market for a second-hand car, it's also worth researching the recommended replacement interval for different models.
Do all cars have cambelts?
Not all cars have cambelts - some have timing chains that last much longer. Electric vehicles don't have a belt or chain; there's no need for one because they don't have an engine.
This guide explains how to tell whether your car has a timing chain or cambelt.
Can I check a cambelt myself?
We wouldn't recommend checking or replacing your cambelt yourself. You'd need expert knowledge to understand what you're doing and what to look for. Getting a mechanic to inspect your cambelt is the safest and most reliable option.
How long does it take to change a cambelt?
It typically takes four to six hours of labour to change a car's cambelt, sometimes longer. The time depends on where the part is located - some are fairly easy to access, while others require the removal of numerous other components.
Worried there might be something wrong with your cambelt? You're in the right place. At FixMyCar, we help drivers find local, reliable car repairs that won't break the bank.
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Ellie is FixMyCar's Content Manager. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers that is easy understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.