Few jobs worry drivers more than the timing belt. Get it right and the engine carries on for years. Leave it too long, or fit a poor-quality kit, and a snapped belt can wreck an engine in seconds. This guide explains the difference between belts and chains, how to find your change interval, and why a genuine kit is worth paying for.
What does the timing belt or chain do?
Inside the engine, the crankshaft turns as the pistons move up and down. The camshafts open and close the valves. The timing belt or chain links the two so that each valve opens at exactly the right moment. On most modern engines the pistons and valves share the same space at different times, so if the timing slips, they can collide. Bent valves, damaged pistons and a large repair bill can follow.
Belt or chain: how to tell which your car has
A timing belt is a toothed rubber belt, usually behind a plastic cover at the side of the engine. A timing chain looks more like a bicycle chain and runs inside the engine, bathed in oil. The easiest ways to check are:
- Look in your service book or handbook for a timing belt change at a set mileage or age.
- Ask a main dealer or specialist with your VIN, which identifies the exact engine. Our guide to using your VIN to order the right part explains why.
- Check the engine code. Many engines are well documented once you know the code.
As a broad guide, many smaller Volkswagen Group petrol and diesel engines use belts, while some larger petrol engines use chains. Most recent Hyundai, Kia and Toyota petrol engines use chains. Some Ford EcoBoost petrol engines use a belt that runs in oil, often called a wet belt, which has its own inspection and replacement schedule. Because manufacturers change designs between engine generations, always confirm for your exact engine rather than relying on the model name.
How often should the belt be changed?
There is no single answer. Manufacturers set intervals by mileage and by age, and you should change the belt at whichever comes first. Depending on the engine, intervals can range from around 40,000 miles to well over 100,000 miles, and age limits are commonly between four and ten years. A low-mileage car that sits a lot still needs its belt changing on age, because rubber hardens and cracks over time.
Your service schedule is the only reliable source for your car. If you have bought a used car with no record of a belt change, it is sensible to treat it as due.
Do timing chains last forever?
Chains are designed to last much longer than belts, often the life of the engine, but they are not maintenance-free. Chains can stretch, and their guides and tensioners can wear, especially if oil changes have been missed or the wrong oil has been used. Warning signs include:
- A rattle from the engine for a few seconds after a cold start
- An engine management light with camshaft or crankshaft correlation codes
- Rough running or loss of power
If you hear a rattle, get it checked promptly. Replacing a worn chain and tensioner is far cheaper than repairing the damage a jumped chain can cause.
Why change the whole kit, not just the belt
A timing belt works with several other parts: a tensioner, one or more idler pulleys and, on many engines, the water pump. These parts wear at a similar rate. If an old tensioner bearing fails a few months after a new belt goes on, the result can be just as bad as a snapped belt. That is why most specialists replace the belt, tensioner and pulleys together, and often the water pump too if it is driven by the timing belt.
The labour is the expensive part of the job. Doing everything at once means you only pay for that labour once.
Why genuine timing parts matter
Timing components work under constant load and heat. Genuine parts are made to the engine maker's specification for tooth profile, belt material, tensioner spring rate and bearing quality. A cheap tensioner with a weak spring or poor bearing can let the belt flap, wear or jump a tooth. Genuine kits also come with the correct new bolts where the manufacturer specifies one-use fixings.
When you order, use the part numbers for your exact engine. Our guide on reading a genuine VW, Audi, SEAT & Skoda part number explains how to spot related parts and revisions, and our guide to exploded diagrams shows how to find every part in the timing assembly.
Signs a timing belt needs attention
Belts often give little warning before they fail, which is why sticking to the interval matters. That said, you may notice:
- A squeal or whine from the front of the engine
- Oil contamination on the belt from a leaking seal
- Cracks, fraying or missing teeth if the belt can be inspected
Oil leaks are worth fixing at the same time, because oil softens rubber belts and shortens their life.
Find genuine timing parts
We stock new genuine parts for a wide range of makes. Browse our Volkswagen, Audi, Ford, Hyundai, Kia and Toyota parts, or search by part number. If you are unsure which kit fits, send us your VIN and we'll help you check.