Timing belt or timing chain? Why it matters for your engine

The timing belt or chain keeps the engine's valves and pistons moving in step. If it fails, many engines suffer major internal damage, so it's worth knowing which yours has.

Timing belt

• A toothed rubber belt behind a plastic cover.
• It must be replaced at a set interval, often between 90,000 and 150,000 km or a number of years, whichever comes first. Your manual or a dealer can tell you the exact figure.
• Replace the tensioner and idler pulleys at the same time, and usually the water pump if the belt drives it.
• If you buy a used car and can't prove when the belt was changed, assume it's due.

Timing chain

• A metal chain inside the engine, lubricated by engine oil. Many modern Japanese engines use one.
• Designed to last much longer, but late oil changes and low oil wear it and its tensioner.
• A rattle for a few seconds at cold start can be a sign of wear. Have it checked.

Not sure which you have? Ask your mechanic, then note it in your vehicle's CarLog record with the date and mileage of any replacement.