The VR6's timing chains are its signature failure — and unlike a belt, they sit at the back of the engine against the bulkhead, so the job is a major one. The narrow-angle VR6 (12-valve AAA/AES in the Mk3, 24-valve BDF/BMJ in the Mk4) runs multiple chains with plastic guides and tensioners that wear.
Symptoms:
- A rattle from the back of the engine, worst on cold start-up.
- Rough running or a cam-correlation / timing fault if a chain has stretched and jumped.
- Worst case, the chain skips and the interference engine bends valves.
The fix:
- Replace the full chain kit — chains, guides, tensioners — as a set; new parts against worn ones won't last. Because the chains are bulkhead-side, most shops pull the engine (or move the front end to a service position).
- On the 24v, the upper, lower and oil-pump chains are all in scope.
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