Cambelt or timing chain: what your car has and when to change it
By James Snow
Owner and mechanic, SV Autos
Updated 25 July 2026
The cambelt is one of the few jobs on a car you really don't want to skip, because on most modern engines a snapped one turns into a very expensive repair in a split second. The catch is that not every car has a belt, and the ones that do all want changing at different points. Here's how to work out which your car has and when it's due, in plain English.
Belt or chain: what's the difference
Both do the same job. They keep the top of the engine and the bottom of the engine turning in time with each other, so the valves open and close at the right moment against the pistons. Get that timing wrong and the engine won't run, or worse, parts collide.
A cambelt (also called a timing belt) is made of reinforced rubber with teeth on the inside. Rubber wears and perishes, so a belt is a service item that has to be replaced on a schedule. A timing chain is metal, like a heavy-duty bike chain, and is designed to last much longer, often the life of the engine. Longer doesn't always mean forever though, which we'll come to.
How to find out which yours has
You can't always tell by looking, because both sit behind a cover. The reliable way is your car's handbook or service schedule, which will list a cambelt change interval if it has a belt. No mention of one usually points to a chain.
If you haven't got the handbook, a quick lookup by registration or by make, model and engine will tell you. Garages and parts sites hold this data, and we can check it for you in a minute if you're not sure. It's worth knowing either way, because it changes what your car needs over its life.
- Check the handbook or service book for a cambelt (timing belt) interval
- No interval listed usually means it runs a chain
- Or look it up by your reg, or by make, model and engine size
- Still unsure? Ask us and we'll check it for you
Why a cambelt is one job you don't skip
Most modern engines are what's called an interference design. That means if the belt snaps or slips, the valves and pistons end up in the same place at the same time and hit each other. The result is bent valves, and sometimes far worse, which often costs more to fix than the car is worth.
A cambelt tends to give little warning before it goes. That's exactly why it's replaced on time rather than when it looks worn. The change is a planned, sensible cost. The failure is a nasty surprise bill, and usually a car that won't start where it stopped.
When it's due (and why the number varies)
There is no single figure that fits every car. Manufacturers set the interval by both time and mileage, typically somewhere in the region of every few years or every several tens of thousands of miles, whichever comes first. Some engines want it much sooner than others, so the only number that matters is the one in your car's schedule.
The time part catches a lot of people out. Even a low-mileage car that mostly sits still has a rubber belt quietly ageing, so a belt can be due on age alone long before the mileage is up. If you've bought the car used and can't find proof it's been done, treat it as unknown and get it checked, because an overdue belt isn't worth the gamble.
Signs to watch, and the water pump question
You often get no warning at all, which is the whole point of changing it on schedule. Sometimes there's a clue: a light rattling or ticking from the timing end of the engine, or a squealing belt, is worth getting looked at rather than ignoring.
On a lot of engines the water pump is driven by the same belt and sits right behind it. Because most of the labour is in getting to that area, it's common sense to change the water pump at the same time as the belt. Doing both together saves stripping the same job down twice, so it's often the cheaper move over the life of the car even though it adds a part now. We'll always tell you up front whether your engine is one where that makes sense.