Timing Chains
A timing chain synchronises the crankshaft with the camshafts so the valves open and close in the correct relationship to piston position. It runs in engine oil and is tensioned hydraulically.
What it does
The chain links the crankshaft sprocket to the camshaft sprockets. A hydraulic tensioner takes up slack and guides control the chain path. Correct timing keeps valves clear of pistons and combustion efficient.
Signs a timing chain is failing
- A rattle from the timing cover on cold start that quietens as oil pressure builds
- Camshaft and crankshaft correlation fault codes
- Rough running or a loss of power
- A rattle that returns under sudden throttle changes
When to replace them
Once treated as lifetime components, but chain stretch and guide wear are common at higher mileage on many modern engines. Investigate any cold-start rattle immediately.
What to confirm before ordering
Have these ready and the counter can usually confirm the part in under a minute.
- Engine code from the block
- Whether the kit includes tensioner, guides and sprockets
- Whether the engine is an interference design
- Whether the front crankshaft seal and cover gasket are needed
Timing Chains questions
What happens if a timing chain fails?
On an interference engine, valves and pistons collide and the engine is destroyed. That is why a cold-start rattle should be investigated straight away rather than monitored.
Should the tensioner and guides be replaced with the chain?
Yes. They wear as a set and the labour to reach them is already spent. A worn tensioner will let a new chain slap and stretch early.