Mercedes-Benz C 250
Compact four-cylinder with mechanical supercharger. Known for timing chain stretch from approx. 100,000 km. Supercharger magnetic clutch can fail. Manual gearbox rare.
High Power, High Risk
150 kW M271 sounds good, but: timing chain. The risk grows with age and mileage. Anyone buying must prioritise chain condition.
Engine Weaknesses 6
The simplex timing chain on the M271 is the most well-known wear issue: it can stretch before 100,000 km. In advanced stages it skips teeth and causes engine damage.
Symptoms: Rattling on cold start (diesel-like noise), camshaft fault codes, check engine light, in extreme cases engine damage
The camshaft adjuster solenoids develop leaks. The wiring harness absorbs oil by capillary action, which migrates as far as the engine ECU and damages it.
Symptoms: CEL with P0010/P0015, oil traces at camshaft connectors, in worst case ECU failure
The camshaft adjuster seals on the M271 become porous and allow oil into the electrical connectors. The result is fault codes and check engine light.
Symptoms: Check engine light, camshaft adjuster fault codes, rough running, oil in adjuster connector
The electronically controlled thermostat on the M271 opens prematurely and prevents full warm-up. Engine stays below 90°C, increased consumption and worse emissions.
Symptoms: Engine doesn't reach operating temperature even after 20+ km, heater stays cold, increased fuel consumption, coolant temperature at 70–80°C instead of 90°C
The ignition coils on the M271 are susceptible to moisture and wear. If one coil fails, the engine runs on three cylinders. Connector contacts often corroded.
Symptoms: Heavy stumbling and power loss, rough running, CEL flashing with misfires, fault codes P0351–P0354
Nearly all M271 engines develop cracks in the part-load ventilation hoses. The result is false air ingestion, increased consumption and elevated oil consumption.
Symptoms: Minor part-throttle malfunctions, hesitation, elevated consumption, occasional check engine light
Vehicle Weaknesses 7
Rear subframe rusts from the inside out. Problem not immediately visible externally. In severe cases the rear differential can shift.
Brake lines corrode relatively quickly and are flagged at MOT. Affected two to several times more frequently than the vehicle average.
W204 rear subframes systematically rust through from the inside. Powder coat cracks and moisture penetrates. Mercedes replaces under goodwill (15 years from first registration). In extreme cases the axle breaks.
Brake lines above the rear axle rust through after approximately 8–10 years. Brake fluid loss and brake failure possible. Mercedes goodwill arrangement known up to 8 years.
Pre-facelift models (up to 2011) show clunking front axles from defective shock absorbers, strut top mounts and wishbones. Improved after facelift.
Xenon headlight levelling actuators fail frequently. Error message and dazzling of oncoming traffic.
Shock absorbers and strut mounts of the front axle wear prematurely on the W204. Rumbling and wallowing typical from 100,000 km.