Timing belt: when to change it, why it matters, and what it costs

What the timing belt does

Inside the engine, two things have to move in perfect step:

• The pistons move up and down in the cylinders and turn the crankshaft, at the bottom of the engine.
• The valves open and close to let air and fuel in and exhaust out. They're pushed by the camshaft, at the top of the engine.

The timing belt is a toothed rubber belt that links the two, so that each valve opens at exactly the right moment for its piston. It runs around a set of pulleys at the side of the engine, behind a plastic cover:

• Crankshaft pulley: at the bottom, driven by the engine.
• Camshaft pulley (or two): at the top. It turns once for every two turns of the crankshaft.
• Tensioner: a spring-loaded pulley that keeps the belt tight.
• Idler pulleys: guide the belt around the engine.
• Water pump: on many engines the timing belt drives the coolant pump too.

Why a broken belt is so expensive. In most modern engines, the valves and pistons use the same space at different moments. These are called interference engines. If the belt breaks or jumps a few teeth, the camshaft stops while the pistons keep moving, and the pistons hit the open valves. The result is bent valves, damaged pistons and often a ruined cylinder head.

Belt, chain or wet belt: which does your car have?

Not every engine has a timing belt. There are three types:

How to find out:

• Look in the service book or owner's manual. If there's a timing belt interval, your car has a belt.
• Ask a dealer or a workshop. With your registration or VIN they can tell you exactly, including which version of an engine you have.
• Don't go by the model alone. The same model can have a belt or a chain depending on the engine and the year.

When you add a car, Track2Drive asks whether it has a timing belt, a wet belt or a chain. If you choose "Not sure", it plays it safe and tracks a timing belt until you know.

Why timing belts wear out

A timing belt is made of rubber reinforced with strong fibres. It doesn't wear like brake pads, but it ages:

• With distance. Millions of turns slowly wear the teeth and stretch the fibres.
• With time. Rubber hardens and cracks with age and engine heat, even if the car is rarely driven. That's why every belt also has an age limit.
• With oil or coolant leaks. Oil or coolant on a dry belt softens the rubber and makes it fail early.
• Through the parts around it. A worn tensioner, idler or water pump bearing can seize or wobble and destroy a new belt.

The trouble is that a timing belt gives almost no warning. It sits behind a cover, it rarely makes noise before it fails, and it can look fine from the outside until the day it breaks. That's why it's replaced on a schedule, not when it looks worn.

When to change it

Your manufacturer's interval comes first. It's in the service book, and it varies a lot: from about 60,000 to 240,000 km, and from about 5 to 10 years. Whichever limit comes first counts.

Track2Drive uses a cautious default when you don't know your car's figure. Your maintenance level and driving style don't change it: a timing belt is changed on schedule, whatever the conditions.

Wet belts: PureTech, EcoBoost and others

On a wet-belt engine, the timing belt runs inside the engine, bathed in oil. It's quieter and more efficient, but the belt's life depends on the oil. Old, diluted or wrong-spec oil attacks the rubber.

You'll find wet belts in Stellantis 1.0 and 1.2 PureTech petrol engines (Peugeot, Citroën, DS, Opel/Vauxhall, and some Fiat, Jeep and Toyota models), and in Ford's 1.0 EcoBoost in some Fiesta, Focus, EcoSport and other models. Newer versions of both engines switched to a timing chain, but not on every model at the same time, so ask your dealer with your VIN.

What goes wrong: a worn wet belt sheds rubber particles. They can block the oil pump's strainer and starve the engine of oil, and the belt itself can break. On some PureTech cars, belt debris also affected the brake servo.

If your car has a wet belt:

• Follow the shorter interval. For the 1.2 PureTech, Stellantis cut its own interval from 10 years or 175,000 km to 6 years or 100,000 km. Many specialists change it sooner. Track2Drive's default is 60,000 km or 4 years.
• Look after the oil. Use exactly the oil your manual specifies and change it on time. Track2Drive caps the oil interval at 15,000 km or 12 months for wet-belt cars.
• Take warning lights seriously. A low-oil-pressure light, or a brake pedal that suddenly feels hard, needs a workshop straight away.

What's replaced with the belt

A timing belt is almost never replaced on its own. Workshops fit a timing belt kit:

• The belt.
• The tensioner and idler pulleys. Their bearings age at the same rate as the belt, and a seized pulley destroys a new belt within minutes.
• The water pump, if the belt drives it. It's behind the belt, so changing it now costs little extra. Changing it later means doing most of the job again, and an old pump that seizes or leaks can ruin the new belt.
• Often the auxiliary belt (the one that drives the alternator and air conditioning), since it has to come off anyway.
• Coolant, when the water pump is replaced.

Warning signs

A timing belt rarely warns you, so don't wait for signs. When there are any, they mean act now:

• A whining, ticking or slapping noise from the side of the engine, especially when cold: often a worn tensioner, pulley or water pump.
• Oil or coolant leaking near the timing cover.
• Cracks, fraying or missing teeth on the belt, if a workshop looks behind the cover.
• The engine runs badly, misfires or is hard to start, with the engine warning light on: the belt may have jumped a tooth.
• A timing belt service light, on cars that have one.
• Wet belts only: the oil pressure warning light, bits of rubber in the oil or filter, or a hard brake pedal (some PureTech cars).

What happens if you don't change it

1. 1Nothing, for a while. An old belt can keep going past its interval, and that's what makes it dangerous: there's no sign until it fails.
2. 2A damaged belt. Cracked or worn teeth, or a worn tensioner, make the belt likelier to slip or snap. Wet belts start shedding debris into the oil.
3. 3The belt jumps a tooth. The engine runs badly, the warning light comes on, and on some engines the valves already touch the pistons.
4. 4The belt breaks. The engine stops at once, wherever you are, including on a motorway.
5. 5Engine damage. On an interference engine, bent valves, damaged pistons and a damaged cylinder head usually cost thousands of euros, and on an older car it can mean the end of the engine. On a wet belt, oil starvation can seize the engine.

Why not just wait for a sign?

• There usually isn't one. A timing belt gives little or no warning before it breaks.
• Low mileage doesn't protect you. The age limit counts even if you hardly drive: rubber hardens and cracks with time. A 10-year-old belt with 40,000 km on it is still due.
• The service book is the right source, but it's easy to lose track. The belt is changed only every few years, the car may change owners in between, and it's rarely done at a routine service.

How a timing belt is changed

1. 1The engine is locked. Special tools hold the crankshaft and camshafts in their exact positions, so the timing can't move while the belt is off.
2. 2The way is cleared. The auxiliary belt, the timing cover and often an engine mount are removed. On some cars, the engine has to be supported or partly lowered.
3. 3The old belt and parts come off: the belt, tensioner, idlers and, if fitted, the water pump.
4. 4The new kit goes on. The belt is fitted exactly on the marks, and the tensioner is set to the specified tension.
5. 5The engine is turned by hand, usually twice, and the timing marks are checked again before anything is started.
6. 6Everything is refitted, the coolant is refilled and bled if the pump was changed, and the engine is test-run.

At a workshop this takes about 3 to 5 hours on a typical engine, and much longer on some (V6 engines, or where the engine has to come out). Wet belts take longer still, because the engine has to be opened.

How much a timing belt change costs

For a typical petrol or diesel engine, a timing belt kit with water pump costs about €230 and the job takes about 3.5 hours, so most of the bill is labour, and that's what changes between countries. A wet belt kit costs about €350 and takes about 5 hours. Figures are estimates for an independent workshop, VAT included.

Questions people ask