Timing chains

How you know it is this

• A rattle for a second or two on a cold start, from the front of the engine
• A timing correlation fault code, often naming camshaft position against crankshaft
• Rough running or a check-engine light that appears with the rattle
• The engine sounding like a diesel when it is not one

Worth knowing before you buy

• A stretched chain does not snap — it jumps a tooth, and then the valves and pistons meet. The rattle is the warning and it is worth acting on.
• Never fit a chain alone. The tensioner and the guide rails wear with it, and a new chain on old plastic guides is back within a year.
• The job usually means the front of the engine comes apart, so the labour is most of the cost. Doing it once, properly, with the full kit is the cheap way.
• Some engines are chain at the rear of the block rather than the front, which changes the labour completely — the gearbox comes out instead.

Rest of the timing

• Timing chain tensioners
• Timing chain guides and rails
• Timing belts and kits
• Camshaft adjusters (phase variators)
• Camshaft adjuster magnets / solenoids
• Timing covers and gaskets