Mercedes-Benz W204 M271 engine timing chain stretch
W204 M271: does the timing chain stretch and when should it be replaced?
Timing chain stretch is a known weakness of the M271 engine, and the chain can jump without warning. Replacement is recommended in good time, usually before 100,000 km. How long the chain lasts varies: some drive well beyond that, while others have the fault much earlier.
How can I tell if the M271 engine in a W204 has a stretched timing chain?
Signs include a rattle or rasping noise from the timing end, a fault code relating to the knock sensor or camshaft position (e.g. P0014), and the engine shaking when starting or switching off. The rattle is not always audible even if the chain has stretched. Before replacing a sensor, check the condition of the timing end; if in doubt, take the car to a workshop immediately.
What is usually replaced during an M271 timing chain job?
Besides the chain and tensioner, the sprockets are often replaced, and on the M271 evo engine also the camshaft adjusters. If the upper sprockets are in good condition, the chain and tensioner may be enough. The wear only becomes clear under the valve cover. If the chain jumps several teeth, the valves can bend.