Is the rattle on my Audi S4 V8 the timing chain?

Short answer: On the B6/B7 S4's 4.2L V8, the timing chains are at the back of the engine, next to the transmission. A very short rattle (about two seconds) on a cold start is considered normal. Longer rattles, misfires or cam-timing codes point to worn guides, tensioners or cam adjusters (parts that change cam timing). Fixing them usually means taking the engine out, which is why the bill is so high.

Symptom: A brief rattle when you start a cold engine, a rattle that is getting longer, a misfire, or a check engine light for camshaft timing.

What to check first

1. Time the cold-start rattle. Owners treat about two seconds as normal. Longer or getting worse is not.
2. Read the codes. Cam timing or misfire codes are a warning sign.
3. Have a shop check cam timing with a scan tool that can read the Audi values.
4. Check oil level and quality. The tensioners run on oil pressure.

Likely causes

1. Worn or broken chain guides. Owners say the guides, tensioners and adjusters fail, not the chains themselves.
2. Tensioners leaking down. Members mention oil check valves in the valley pan that can leak down and cause cold-start rattle.
3. Worn cam adjuster. One owner's worn adjuster caused a misfire and over-advanced timing codes.

What it usually costs

Owners in these threads cite estimates of about $4,000–8,000 for the timing job, and one said a dealer paid over $12,000 for a new engine on an '05. Prices are from owner posts and vary by shop.

Is it safe to keep driving?

A short cold-start rattle alone isn't an emergency, but if the rattle is long or the car is misfiring, get it checked before driving hard or far. A guide failure can cause major engine damage. Verify with a mechanic.

DIY or shop?

Shop job. The chains are at the back of the engine, so the engine usually comes out. Find an Audi specialist who has done it before.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists no recall for the engine timing chain on the Audi S4 for these model years (checked 2026-10-23). Other recalls may exist for your car, so check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• NHTSA complaints: 12 keyword-matched complaints for Audi S4 2004–2008 (of 106 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-23; keywords: timing, chain, guide, tensioner, rattle, camshaft, adjuster) (NHTSA returned no complaint data for 1 model-year queries). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Timing chain rattle on Audizine, members said a rattle of about two seconds on a cold start is normal on this engine. They mentioned oil check valves in the valley pan that can leak down and said broken guides mean an engine-out repair.
• In Odds of having timing chain issues in B6 S4 on Audizine, owners said it's the guides, tensioners and adjusters that fail, not the chains. They cited $4,000–8,000 estimates, and one said a dealer paid over $12,000 for a new engine on an '05. Another said a worn cam adjuster gave him a misfire and over-advanced timing codes, and that 2007–2008 cars got updated guides.

Quick tip

If you're shopping for a B6 or B7 S4, ask for proof the timing job was done or budget for it. A pre-purchase scan of cam timing values is worth paying for.

Vehicle focus: 2004–2008 Audi S4 (B6 and B7) with the 4.2L V8. The RS4 uses a different version of the engine.

Safety / mechanic note

A failing timing chain guide can lead to serious engine damage. Verify with a mechanic.