Timing Belt or Timing Chain: What Is the Difference?

Timing belts and timing chains perform the same basic job: they keep the crankshaft and camshaft moving in the correct relationship so the valves open and close at the right time. If that timing is lost, the engine can stop instantly and, on many engines, internal damage can follow.

The difficulty for drivers is that timing systems vary widely. Some engines use a conventional dry belt, some use a chain, and some modern engines use a belt that runs in engine oil, often called a wet belt.

Timing belts

Conventional timing belts usually have a replacement interval based on age, mileage or both. The exact interval depends on the engine, so it should be checked against the manufacturer information for that vehicle. Replacing the belt before it reaches the end of its service life is far cheaper than dealing with the damage that can follow a failure.

A timing-belt job may also involve tensioners, idlers and, on some engines, the water pump. Reusing worn associated parts can undermine the value of fitting a new belt.

Wet timing belts

Wet belts operate inside the engine and are exposed to oil. They rely heavily on the correct oil specification and maintenance history. If the belt material deteriorates, debris can circulate through the lubrication system and may restrict oil pick-up or contaminate other components.

Wet-belt replacement should therefore be approached as more than simply removing one belt and fitting another. The condition of the lubrication system and related components may also need attention.

Timing chains

Timing chains are often described as lasting the life of the engine, but that does not mean they cannot wear. Chains can stretch, guides can break and tensioners can lose control. Oil quality and oil-change history can have a major effect on chain systems.

Common warning signs

• Rattling on cold start
• Timing correlation fault codes
• Difficult starting
• Rough running
• Loss of power
• Metallic noise from the timing area
• Visible belt deterioration where inspection is possible

What happens if the timing fails?

On an interference engine, the pistons and valves occupy the same physical space at different times. If the camshaft and crankshaft lose synchronisation, valves can contact the pistons. Damage can include bent valves, broken rockers, damaged cam components and cylinder-head damage.

After a failure, simply fitting a new belt or chain may not be enough. The engine often needs further assessment before the repair can be planned properly.

Timing work in Ruislip

At Capital Garage we carry out timing-belt, wet-belt and timing-chain work for a range of cars and vans. We use the correct locking and timing procedures and consider associated components before reassembly.

For more information, visit our timing belt and timing chain service page or book an appointment.