Cambelt intervals: when to replace a timing belt

A cambelt (timing belt) is changed on a schedule set by the car's manufacturer, and the schedule is given in both years and miles: whichever comes first. The right interval is the one in the handbook or service schedule for that exact engine, not a general rule of thumb. When you are buying, the decision is simple. If the car is at or past its interval and the seller cannot show an invoice for the job, treat the belt as due and price the work into your offer.

What a cambelt does

Inside the engine, the crankshaft turns as the pistons go up and down. The camshafts open and close the valves. The two have to stay in exact step, so each valve opens only when its piston is out of the way. On many engines a toothed rubber belt links them. That is the cambelt.

The belt sits behind plastic covers at one end of the engine, so you usually cannot see it without taking parts off. It wears with age and use. Rubber hardens and cracks over time even when the car is parked, which is why the interval has a time limit as well as a mileage limit.

Some engines use a metal timing chain instead of a belt. Chains are not on a fixed replacement schedule in the same way. Our guide to timing chains and timing belts explains the difference and how to find out which one a car has.

How intervals are set: years and miles

Each manufacturer sets its own cambelt interval for each engine. It is printed in the handbook or the service schedule, and a franchised dealer can look it up for a specific car. You will see it written as a number of years and a number of miles, with the words "whichever comes first".

Three things follow from that:

• A low-mileage car still needs a belt. A car that has done few miles can reach the time limit long before the mileage limit. Age matters as much as distance.
• Intervals differ between engines. Two cars that look the same can have different engines and different schedules. Check the schedule for the engine, not just the model name.
• Intervals can change. Manufacturers sometimes revise a schedule after launch. A franchised dealer or a good independent garage can tell you the current figure for the car.

We do not give generic interval figures here, because a wrong number is worse than no number. Ask for the schedule for the car you are looking at.

Belts that run in oil

Some newer engines run the belt inside the engine, in oil, rather than dry behind a cover. These have their own schedule and can be sensitive to the engine oil being the correct grade and changed on time. If the car has one, the service history matters even more.

Why a snapped belt can be so expensive

If a cambelt breaks while the engine is running, the camshafts stop turning but the crankshaft keeps going. What happens next depends on the engine design.

On an interference engine, the valves and pistons share the same space at different moments. With the timing lost, a piston can hit an open valve. That can bend valves and damage pistons and the cylinder head. The repair can cost more than the car is worth, which is why many interference-engine cars are scrapped after a belt failure.

On a non-interference engine, there is enough room that the pistons and valves do not meet. The engine stops and the car needs recovering, but the internal damage is usually far less.

Most buyers will not know which type a car has, and you do not need to. Treat every overdue belt as a serious risk and plan for the job before you drive the car far.

The water pump and other parts changed at the same time

On many engines the water pump is driven by the cambelt, or sits behind the same covers. Garages often recommend changing it at the same time, because most of the labour is already done. If the old pump fails later, it can leak coolant onto the new belt or seize and damage it.

A cambelt job is often sold as a kit, which may include:

• the belt itself;
• the tensioner, which keeps the belt tight;
• one or more idler pulleys, which guide the belt;
• the water pump, where it is driven by or sits behind the belt;
• fresh coolant, if the pump is changed.

When you read an invoice, look at which of these were fitted. "Cambelt changed" on its own tells you less than an itemised list.

What the MOT does and does not tell you

The MOT does not check the cambelt. The test is done without taking parts apart, and the belt is hidden behind covers. On a diesel, the inspection manual tells the tester not to do the smoke test if the camshaft belt is in an unsatisfactory condition, but that is a safety step, not a check of when the belt was last changed. Our guide to what the MOT does not check covers this and other gaps.

The MOT history is still useful. GOV.UK says to check that the MOT status and history match what the seller tells you. Each test records the mileage. You can use those readings to see how far the car has travelled since a cambelt invoice was dated, and whether the next change is close. Our guide to reading MOT history explains how.

Checking the cambelt history as a buyer

Ask the seller for the invoice. A stamp in a service book is weaker evidence, because a stamp rarely says what was done. A good invoice shows:

1. the date of the work and the mileage at the time;
2. the garage's name and contact details;
3. the parts fitted, ideally listed one by one;
4. the vehicle details, such as the registration or VIN, so you know the invoice belongs to this car.

Then compare the date and the mileage with the manufacturer's interval. If either is close, the next change is close too.

Some garages put a sticker under the bonnet with the date and mileage of the last change. That is a helpful clue, not proof. Anyone can write on a sticker. Use it as a reason to ask for the invoice.

If you want to check that the work was really done, call the garage named on the invoice. Give them the date and the mileage and ask whether they did a cambelt job on that car. Most garages will confirm a job without sharing the owner's details. Our guide to full service history covers how to verify records more generally.

When there is no record

If there is no invoice, assume the belt has not been changed. That is the safe default. A seller may say "it was done by the last owner", but without paperwork you cannot know when, at what mileage or which parts were fitted.

You then have three sensible options:

• Negotiate. Our guide to negotiating a used car price covers how. Get a written quote for a cambelt and water pump job on that engine from a local garage, and reduce your offer by that amount.
• Ask the seller to do it. Agree a price on the condition that the job is done before you collect, and ask for the invoice.
• Walk away. If the seller will not move and the car is clearly past its interval, another car may be a better buy.

Whatever you choose, do not put off the job after you buy. Budget for it from day one. If you want a second opinion on the car before you commit, see the car and ask a mechanic.

Frequently asked questions

How often should a cambelt be changed?

As often as the manufacturer says for that engine. The interval is given in years and miles, and you change the belt at whichever comes first. Find it in the handbook or service schedule, or ask a franchised dealer.

Does the MOT check the cambelt?

No. The belt sits behind covers and the MOT is done without taking parts apart. Ask the seller for the invoice for the last change.

Can you tell if a cambelt has been changed by looking at it?

Not reliably. The belt is usually hidden, and a sticker under the bonnet is only a clue. The invoice, with the date, mileage and parts fitted, is the evidence to ask for.

Does a low-mileage car still need a cambelt change?

Yes, if it has reached the time limit. Rubber ages even when the car is parked, which is why the interval has a time limit as well as a mileage limit.

Should I walk away from a car with an overdue cambelt?

Not always. An overdue belt is a known cost. Get a quote, negotiate the price down or ask the seller to do the job first. Walk away if the seller will not do either.