Plastic guide rails hold the timing chain in place. On these engines the plasticiser in the plastic leaches out over time, the rail turns brittle and then breaks into pieces. The pieces land around the chain and further down, in the oil sump and on the strainer of the oil pump, and the leached plasticiser also deposits on that strainer. Two kinds of damage come from this: without its guide the chain starts to flap, and less oil reaches the engine through the narrowing strainer. The first sign is a rattling noise on a cold start that goes quiet after a few seconds or once the engine has warmed up. It is heard best on a fully cold start in the morning, because the chain tensioner needs time to tension the chain. The problem is reported above 60,000 km. Replacing the chain costs between 700 and 2,900 euro, and is typically four figures, because the chain can only be reached by removing several engine components.
What to check
- Start the engine fully cold in the morning and listen for the rattling noise
- Ask whether the chain and the guide rail have been replaced, and ask for the invoice
- Ask when the oil was last changed and how often the car was serviced
