Mercedes-Benz C 180 CDI
Robust two-litre diesel with common rail. Known for leaking injector seals and DPF issues under short-trip use. Otherwise long-lived.
Emergency Four-Cylinder
88 kW in the W204 — too little engine for too much car. The OM640 isn't a bad engine, just misplaced in the C-Class.
Engine Weaknesses 6
The OM640 injectors loosen and develop leaks in service. From approximately 150,000 km, tarry gases enter the engine bay and the cabin. All injectors should be replaced simultaneously.
Symptoms: Knocking 'psch-psch-psch' noise, engine warning light, soot deposits around injectors, misfires, diesel smell in the cabin
The OM640 shows metallic rattling at cold start from approximately 150,000 km due to timing chain stretch. Complex removal as the engine in the W169/W245 is mounted at an angle and must be lowered.
Symptoms: Metallic rattling at cold start, noise fades when warm, knocking on load changes, CEL possible
The EGR valve on the OM640 tends to coke up with soot deposits, particularly during frequent short-trip use. A stuck EGR valve significantly worsens performance and fuel economy.
Symptoms: Poor throttle response, elevated fuel consumption, engine warning light, rough idle, soot clouds under acceleration
The diesel particulate filter on the OM640 does not regenerate adequately during short-trip driving. Insufficient exhaust temperatures leave soot in the filter and block it.
Symptoms: DPF warning light, power loss, elevated fuel consumption, engine enters limp mode
The DMF on the OM640 in the A180/B180 CDI is known for premature wear. Mercedes acknowledged the problem and announced an improved version.
Symptoms: Loud rattling from engine bay when warm, noise disappears when pressing the clutch, vibrations when pulling away and manoeuvring
The oil cooler on the OM640 is prone to leaking gaskets at the oil filter housing. Oil traces on the heat shield under the engine. Gasket replacement resolves the issue.
Symptoms: Oil spots on underbody cladding, oil smell after shutdown, dropping oil level without visible external leak
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.