Question 1

What is the OM651 Diesel Chain Tensioner Oil Leak issue on the Mercedes-Benz C-Class (W204)?

Accepted Answer

The gasket on the timing chain tensioner can fail, leaking oil and potentially leading to timing chain issues due to inconsistent tension. Symptoms include: Oil leaking onto the right side of the engine block, Rattle on cold start. Estimated repair cost: £200–£450.

Question 2

What is the Rear Subframe Corrosion issue on the Mercedes-Benz C-Class (W204)?

Accepted Answer

The rear subframe rots from the inside out, leading to MOT failure. Mercedes often replaces these under goodwill. Symptoms include: Heavy corrosion noted by MOT, Rust on suspension mounts. Estimated repair cost: £0 (Goodwill) – £1,500.

Question 3

What is the Electronic Steering Lock (ESL) failure issue on the Mercedes-Benz C-Class (W204)?

Accepted Answer

The electronic steering lock module can fail, preventing the car from starting. The key is recognised but the steering remains locked. A common and expensive fault on W204s built before the facelift. Symptoms include: Key recognised but engine won't crank, Steering lock warning on dash, Intermittent no-start conditions. Estimated repair cost: £400–£1,200.

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