Timing chain replacement

A timing chain does the same job as a cambelt, keeping the top and bottom of the engine in step, but it runs inside the engine in oil.

What timing chain means

Chains were once considered lifetime parts; on some modern engines they stretch and the guides wear, and the chain, guides and tensioner are replaced as a set.

What the job covers

Timing chain, guides and tensioner replacement
Chain stretch diagnosis from live data
Variable valve timing faults
Cold-start rattle investigation
Oil-feed and pressure checks

When you might need it

A rattle for a second or two on a cold start, which is the classic sign.
An engine management light with a timing correlation fault recorded.
The engine feeling rougher or less responsive than it was.

What it costs, and what changes the price

Typically £600 to £1,800.

Access. On some engines the chain is at the gearbox end and the engine has to come out.
The kit is chain, guides and tensioner together, since replacing one alone rarely lasts.
Oil and filter are changed afterwards as a matter of course.

How long it takes

A day on accessible engines, two or more on the rest.

Common questions

Is a chain better than a belt?

Neither is better in general. A chain usually lasts longer but costs more to replace; a belt is cheaper but has a fixed schedule.

What does that cold start rattle mean?

Usually the tensioner has lost pressure overnight and takes a moment to take up the slack. It is worth investigating early, because a chain that jumps can damage the engine.

Does oil affect chain life?

Very much. Chains are lubricated by engine oil, and long or neglected oil intervals are the most common reason they wear early.