A timing chain and a timing belt do the same job: they turn the camshafts in step with the crankshaft so the valves open at the right time. A chain is metal, runs in oil inside the engine and is designed to last a very long time, while a belt is reinforced rubber outside the engine and must be replaced at the interval in the owner’s manual. Worn chains rattle on startup and can set cam and crank correlation codes such as P0016.
Timing chain vs timing belt
| Timing chain | Timing belt | |
|---|---|---|
| Material | Metal chain | Reinforced rubber belt |
| Location | Inside the engine, lubricated by oil | Outside the engine under a cover |
| Service life | Designed for a very long life, but guides and tensioners wear | Replaced on a set interval |
| Warning signs | Rattle, timing codes, metal in the oil | Often fails with little warning |
| If it fails | Engine stops; can damage valves | Engine stops; on interference engines, valves hit pistons |
Most V8 truck engines, including the GM LS and Vortec engines, the 5.7 Hemi, the Ford 5.4 Triton and the Cummins, use chains or gears rather than belts.
Timing chain symptoms
- Rattle on cold start that fades as oil pressure builds, from a stretched chain or worn tensioner.
- Check engine light with cam and crank correlation codes such as P0016, because a stretched chain shifts the cam timing.
- Misfires or rough running; see engine misfire.
- Metal particles in the oil from worn guides.
Cam phasers and variable valve timing
Many engines use cam phasers that rotate the camshaft relative to the chain to vary valve timing. Worn phasers knock or tick at idle and can set timing codes. The 3-valve Ford 5.4 Triton is especially well known for cam phaser and timing chain problems; see 5.4 Triton problems.
What keeps a timing chain healthy
- Change the oil on schedule with the specified viscosity; chains and hydraulic tensioners depend on clean oil.
- Investigate a startup rattle early, before guides break and the chain jumps a tooth.
- Fix low oil pressure promptly; see low oil pressure.
Repair or replace the engine?
A timing chain job replaces the chain, guides, tensioners and often the phasers. If the chain has jumped or broken and bent valves, the repair grows quickly, and a replacement long block can be the simpler route; see short block vs long block and our engines by engine code.
More guides: VVT solenoid · camshaft position sensor · timing belt · what does a camshaft do? · bad cam phaser symptoms.
Trouble codes: P0016 Crank/Cam Correlation Bank 1 A · P0017 Crank/Cam Correlation Bank 1 B · P0018 Crank/Cam Correlation Bank 2 A · P0019 Crank/Cam Correlation Bank 2 B · P0011 Intake Cam Timing Over-Advanced · P0014 Exhaust Cam Timing Over-Advanced · P0008 Engine Position System Bank 1 · P0015 Exhaust Cam Over-Retarded Bank 1 · P0024 Exhaust Cam Over-Advanced Bank 2 · P0025 Exhaust Cam Over-Retarded Bank 2 · all OBD2 codes.
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