Mercedes-Benz C 250d
Widely used Mercedes diesel with aluminium block and steel liner. High mileages possible but known for injector seal issues, timing chain stretch and EGR problems.
Strong CDI in the W205
150 kW CDI turns the W205 into a comfortable touring machine. Not exciting, but effective and not annoying.
Engine Weaknesses 6
Over 100,000 vehicles recalled: the chain tensioner seal leaks, allowing engine oil to drip onto the exhaust system and potentially ignite.
Symptoms: Dropping oil level, oil smell from engine bay, oily deposits under the vehicle, possible oil fire
The OM651 uses a simplex timing chain. With short-trip driving and overdue oil change intervals the chain stretches.
Symptoms: Light rattling noise on cold start from the rear of the engine, no fault code stored
Same Delphi piezo injector problems as in the DE18: 220 CDI and 250 CDI variants affected. Mercedes replaced them with solenoid injectors as part of a service action.
Symptoms: Vibrations and rough running especially under acceleration, elevated fuel consumption
The EGR cooler of the OM651 develops hairline cracks at the connection stub and loses coolant. Green staining next to the fuel filter under the engine cover is typical.
Symptoms: Dropping coolant level without visible leak, intermittent coolant warning, green spots under the vehicle, heater output diminishing
The DMF on the OM651 suffers under the high torque output. Documented case: all 8mm rivets sheared at 149,000 km, with consequential damage to the clutch and crankshaft speed sensor.
Symptoms: Rattling and juddering at warm idle, vibrations when pulling away, shuddering at low RPM, noise increases with warm engine
From around 150,000–180,000 km the OM651 turbocharger leaks oil through worn bearings, which drips onto the EKAS intake port deactivation actuator and destroys it. Double damage.
Symptoms: Black smoke under acceleration, oil residue in charge air hose, power loss, fault code P0299 boost pressure underrun
Vehicle Weaknesses 7
Longitudinal members, jack-point attachment holes and rear axle subframe rust through. MB offers goodwill replacement.
Polycarbonate blind cover of the panoramic roof incorrectly bonded. When opening, the blind can come loose. Recalled by MB.
Ball joints on the wheel-side wishbone and rubber-metal bushes wear. New suspension geometry makes repairs more involved.
Some W205 models discharge the battery unusually quickly during extended parking. Cause: elevated quiescent current draw from control units.
The W205 shows above-average front axle issues from the second MOT onwards according to TÃœV statistics. Worn control arms and drop links are the main causes.
W205 A/C fails with 'Air conditioning off' without a fault code in the onboard computer. Often the compressor or A/C control unit is defective.
Panoramic roof on the W205 creaks when opening and closing. Guide linkage can bend and jam the roof. Repair often requires complete removal.