A significant quality improvement over the W203 predecessor, the W204 C220 CDI is a comfortable executive saloon with good fuel economy. Two engine variants exist: the earlier OM646 (2007-2009, single turbo) is considered more reliable, while the OM651 (2008-2014, twin turbo) had early piezo injector issues that were recalled. Key concerns: timing chain tensioner wear on OM651 engines (engine-out job if it fails), electronic steering lock (ESL) failures on 2007-2010 models, DPF blockages from short trips, and rear light wiring burn-out. Rear subframe corrosion affects pre-2013 cars. Overall reliable for a premium diesel when maintained, but repairs can be expensive due to complexity.
The OM651 uses a simplex (single-row) chain at the rear of the engine, unlike the older duplex design. A faulty tensioner allows the chain to rattle on cold starts for 1-30 seconds. Typically occurs between 100,000-180,000 km. If ignored, the chain can skip and cause catastrophic valve damage. The repair is labor-intensive (some specialists can do it without engine removal for around €1,500, but many shops quote €2,500-3,500). Mercedes has released updated tensioner parts. The older OM646 engine (pre-2009) is less prone to this issue.
Electronic steering lock (ESL) failure€400 - €800
Steering stays locked, car won't start - caused by worn motor brushes - more- less
The ESL motor uses carbon brushes that wear out after 8-10 years regardless of mileage. When it fails, the steering wheel stays locked and the car won't start. Mercedes dealers charge €800-1,500+ because they replace the entire unit. Specialists offer repair services for €300-500 that replace just the worn motor/brushes, or install an ESL emulator (€250-400) which bypasses the lock entirely but permanently disables the steering lock security feature. Most affected: 2007-2010 model years.
Piezo injector failure (early OM651)€800 - €2,400
Early BlueEfficiency models had faulty Delphi injectors - most now recalled - more- less
The early C220 CDI BlueEfficiency (2008-2010) used piezo injectors that failed due to an unauthorized design change by Delphi. Mercedes recalled these and replaced them free of charge. How to identify: piezo injectors have no fuel return lines, while the later solenoid injectors do have return lines. If buying an early car, verify the recall was completed. If you need to replace injectors now, expect €200-400 per injector plus labor. Each injector must be coded to the ECU after installation.
DPF blockage€400 - €1,800
Diesel particulate filter clogs from short trips, city driving - more- less
The DPF becomes saturated with soot when the engine doesn't reach temperature for regeneration - common in city-only or short-trip driving. Symptoms: reduced power, DPF warning light, increased fuel consumption. Options: forced regeneration at a garage (€100-200), professional DPF cleaning (€300-500), or replacement (€800-1,800). Mercedes recommends a good motorway run every few weeks to allow passive regeneration. Recommended replacement interval is around 120,000 km if properly maintained.
Rear light wiring burn-out€100 - €350
Thin ground wire overheats, causing bulb warnings and potential fire risk - more- less
The brown ground wire in the rear light cluster is too thin for the electrical load. It overheats, causing burnt connectors and intermittent bulb failure warnings. In severe cases, owners have reported smoke and small flames from the connector. A recall was issued for 2008-2011 models. DIY fix: install a bypass earth wire (€20-50 in parts). Professional repair with new bulb board and connector: €100-350 per side. Mercedes has updated the bulb carrier design multiple times.
Turbocharger failure€1,200 - €2,800
Twin-turbo OM651 can have issues with turbo switching and actuator wear - more- less
The OM651 runs sequential twin turbos. Issues can occur when the car doesn't switch to the high-speed turbo properly, resulting in lack of power at higher RPM. Can also be caused by air leaks from intercooler hoses. Symptoms: limp mode, lack of power above 2,500 RPM. A remanufactured turbo costs around €800-1,200, plus €400-600 labor. Full turbo replacement at a dealer can reach €2,500-2,800. The single-turbo OM646 is simpler and less prone to these issues.
EGR valve clogging€400 - €800
Carbon buildup restricts EGR, causing power loss and warning lights - more- less
The EGR valve and passages become clogged with carbon deposits over time, especially with city driving. Symptoms: check engine light, ESP warning, loss of power, increased fuel consumption. The EGR can fail open or closed - both cause problems. Cleaning sometimes works temporarily but replacement is often needed. Parts cost €150-300, labor adds €200-400. When replacing, the EGR passages should be cleaned as well.
Door lock actuator failure€200 - €600
Internal spring breaks, door won't lock/unlock with remote - more- less
The door lock actuators contain a small spring that eventually breaks. When this happens, the door won't respond to the remote or interior switches. Mercedes dealers charge €600+ per door. Independent garages charge around €200-350. DIY repair is possible if you're willing to remove the door panel - the actuator console costs around €150-200 for genuine parts. The actual spring that fails costs only a few euros, but requires disassembling the actuator.
Rear subframe corrosion€800 - €2,500
Subframe rusts from inside out, often missed on inspections - more- less
The rear subframe can corrode from the inside, with large holes forming on the upper surface that are almost invisible from below. This is a known issue on pre-2013 W204s. Some owners have had free replacement under Mercedes anti-corrosion warranty (verify with dealer using VIN). Often missed during inspections - many W204s are now failing roadworthiness tests for this reason. If out of warranty, expect €800-2,500 for subframe replacement including labor.
Alternator failure€400 - €750
Typically fails between 100,000-150,000 km - more- less
Alternator failure is one of the more commonly reported electrical issues. The alternator typically lasts 150,000-200,000 km but can fail earlier. Symptoms: battery warning light, dimming lights, difficulty starting. Mercedes dealers charge €700-900 for replacement. Independent shops charge €400-600 using quality remanufactured units. If only the pulley is stuck, that's a €100 fix. Some owners report success with having the existing unit rebuilt (new bearings and brushes) for €200-300.
Reliable when maintained, but premium repair costs
The W204 C220 CDI marked a significant improvement in Mercedes build quality. The earlier OM646 engine (2007-2009) is considered more reliable than the OM651. Most issues are well-documented and can be diagnosed before purchase with proper inspection. Avoid cars used primarily for short trips (DPF issues) and verify all recalls have been completed.
Pre-Purchase Inspection Checklist
General checks
Service history Complete Mercedes dealer or specialist records essential. Oil changes every 15,000-20,000 km with approved oil.
Tires Check tread depth, age, and uneven wear patterns. Standard size 205/55 R16.
Cold start Must start engine completely cold. Listen for unusual sounds in first 30 seconds.
Body condition Check for rust, accident damage, paint mismatch. Inspect wheel arches and door bottoms.
Test drive Minimum 30 minutes including motorway speeds to allow DPF regeneration cycle.
Specific for this vehicle
Cold start timing chain rattle (OM651) Listen for chain rattle in the first 10-30 seconds after a completely cold start. This is the most critical check for OM651 engines. Any rattle beyond a brief initial tick indicates tensioner wear.
Check injector type on early BlueEfficiency models Piezo injectors (no return lines) = verify recall completed. Solenoid injectors (with return lines) = good. Look at the injectors under the engine cover.
Test electronic steering lock Turn ignition on/off several times. If there's any hesitation in steering unlock or starting, the ESL may be failing. Check for any warning lights.
Inspect rear light connectors Open the boot and check the rear light wiring for any signs of burning, melting, or brown discoloration on connectors. Verify recall completed for 2008-2011 models.
Check rear subframe for corrosion Put the car on a lift and inspect the rear subframe from multiple angles - corrosion often forms on the top surface that's invisible from below. Use a light and mirror if needed.
DPF health check Ask for a diagnostic readout of DPF soot loading and ash levels. High values indicate the car was used primarily for short trips.
Test all door locks Lock and unlock each door individually with the remote and with the interior switches. Any door that doesn't respond indicates actuator wear.
Check for boost leaks Listen for high-pitched whistling under acceleration which indicates split intercooler hoses - a common issue.
Steering force issue (Jun 2009 - Feb 2010 build)Verify completed
Timing chain tensioner seal leak (Feb-Nov 2014 OM651)Verify completed
Fuel filter leak (OM642 V6, Nov 2009 - Jul 2011)N/A for C220 CDI
Contact Mercedes-Benz with the VIN to verify all applicable recalls have been completed. The piezo injector recall and rear light wiring recall are particularly important for early W204 models.
Warranty Status
Factory warranty (2 years)Expired on all W204s
Anti-corrosion warranty30 years from new (conditions apply)
Mercedes extended warrantyAvailable up to 12 years old
All W204s are outside their original factory warranty. However, Mercedes offers a 30-year anti-corrosion warranty - if rear subframe corrosion is found, contact a dealer with the VIN to check eligibility. Requires complete dealer service history. Extended warranties are available through Mercedes dealers for cars up to 12 years old.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.