Mercedes-Benz C220d W205

This is one of the most commonly reported issues on the W205 C220d. The NOx sensors, located in the exhaust, are vulnerable to water condensation and corrosion. Early-production sensors were of questionable quality and Mercedes replaced many under goodwill. Symptoms include AdBlue warning messages, check engine light, and eventually a countdown warning that the engine will not restart after a set number of kilometres. A single sensor costs around €400-600 to replace; the car has two. In some cases the AdBlue pump inside the tank also fails, pushing total repair cost to €1,500-2,000 including the tank assembly. Mercedes has issued a technical fix involving drilling a drainage hole in the exhaust to prevent condensation buildup. Cars from 2015-2017 are most commonly affected. Independent specialists report seeing this issue regularly.

The OM651 timing chain is located at the rear of the engine, which makes replacement more labour-intensive. Chain stretch develops gradually, typically becoming noticeable between 120,000 and 200,000 km. The first symptom is a brief rattle on cold start lasting 1-5 seconds as the tensioner takes up slack. Mercedes provides a measurement-based guideline: if chain elongation exceeds 82 mm below 250,000 km, replacement is needed. Regular oil changes with quality oil significantly slow chain wear. Replacement involves the chain, guides, tensioner, and sprockets. At an independent shop, expect €1,200-1,800; at a Mercedes dealer, €2,000-2,500. The OM654 facelift engine has a front-mounted chain that is cheaper and easier to service.

The EGR valve on the OM651 accumulates carbon deposits over time, particularly in cars used predominantly for short trips or city driving. Symptoms include rough idling, reduced power, increased fuel consumption, and sometimes a check engine light. Cleaning the EGR valve costs around €200-400 at an independent shop. If the valve is beyond cleaning and needs replacement, parts cost approximately €300-500 plus labour, bringing the total to €600-1,200 at a dealer. Modern Mercedes diesels have the EGR programmed into the engine management in a way that makes deletion or blanking impractical without fault codes and limp mode.

Known in Mercedes diesel circles as 'black death', this occurs when the copper sealing washers under the fuel injectors degrade. High combustion pressures gradually compromise the seal, allowing hot gases to escape. This creates hard black carbon buildup around the injector wells. Caught early, the fix is straightforward: new copper washers, stretch bolts, and cleaning of the injector seats — around €300-500 at a specialist. If left unaddressed, the carbon deposits harden to the point where injectors cannot be removed without special extraction tools, and the repair can reach €1,000-1,500. A diesel smell in the engine bay is an early warning sign. Regular inspection at service intervals prevents escalation.

The DPF needs periodic regeneration, which requires sustained driving at speeds above 60 km/h for 15-20 minutes. Cars used primarily for short urban trips fail to complete regeneration cycles, leading to progressive soot accumulation. When soot loading reaches critical levels, the car enters limp mode and displays a warning. A forced regeneration at a garage costs around €100-200 and is often successful. If the filter is beyond regeneration (soot level above 400%), replacement is needed: aftermarket DPF units cost €600-1,000, while OEM replacement can reach €2,000-2,500 including fitting. The DPF is designed to last 150,000-200,000 km with normal mixed driving.

The OM651 uses electrically controlled swirl flaps in the intake manifold to optimize airflow at different engine speeds. The actuator motor can fail, triggering a P200A fault code and reduced engine performance. Mercedes does not sell the actuator separately — the official fix is a complete intake manifold replacement at approximately €1,000-1,500 at a dealer. However, specialist repair shops can often source and fit just the actuator motor for €400-600. This issue is more common on higher-mileage cars, typically appearing after 100,000 km.

The W205 uses an electric power steering system where the motor is integrated into the steering rack. The main bearing can wear over time, producing a grinding or whining noise when turning the steering wheel. In more serious cases, the power steering assistance becomes intermittent, triggering a 'Power Steering Malfunction' warning. Mercedes treats the rack, motor, and control module as a single unit, quoting €2,000-2,500 for replacement at a dealer. Independent specialists and remanufactured units can reduce this to €1,200-1,800. This is not a widespread issue but affects a notable number of higher-mileage W205s.