Mercedes-Benz B220 CDI W246

The Getrag 7G-DCT (724.0) dual-clutch gearbox is the most common complaint on W246 diesel models. The B220 CDI's 350 Nm of torque puts substantially more stress on the dry clutch packs than both the petrol variants and the B200 CDI (300 Nm). Symptoms include jerking at low speeds, vibrations between 20-40 km/h, hesitation when pulling away, and clutch slippage when hot. Problems typically appear between 60,000-100,000 km on the B220 CDI — earlier than the B200 CDI due to the higher torque load, especially on cars used predominantly in city traffic. Over 70% of faulty gearboxes reportedly never had an oil change in the first 100,000 km. Mercedes considers the gearbox oil a lifetime fill, but specialists strongly recommend changing it every 60,000 km with MB 236.21 specification fluid. A clutch pack replacement costs approximately 900-1,400 with aftermarket parts, 1,500-2,000 with OEM. Mechatronics repair or replacement runs 1,200-3,000. A TCU software adaptation reset (100-200) can improve shift quality in early-stage symptoms.

The DPF on the OM651 requires the engine to reach full operating temperature and sustain approximately 2,000 rpm at 60+ km/h for regeneration. Cars used primarily for short urban trips accumulate soot beyond the point where passive regeneration is possible. Symptoms include the DPF warning light, reduced power, limp mode, and increased fuel consumption. A forced regeneration at a workshop costs 100-200. Professional off-car cleaning costs 300-500. Complete DPF replacement costs 1,200-2,000 including the catalytic converter section. The differential pressure sensor can also fail, preventing regeneration even on highway-driven cars (sensor replacement: 150-250). Check the engine oil level before buying: if it is significantly above the maximum mark, diesel has been contaminating the oil from failed regenerations. Regular motorway driving of at least 30 minutes per week significantly reduces the risk.

The OM651 uses a single-row (simplex) timing chain rather than a more durable duplex chain — this was acknowledged by Mercedes when the successor OM654 switched to a duplex design. The chain is located at the rear of the engine, making replacement labor-intensive. Symptoms begin as a distinctive metallic rattle for 1-5 seconds on cold start as the tensioner loses hydraulic pressure overnight. This typically starts between 120,000-180,000 km with proper oil changes, but can occur earlier with neglected maintenance. The B220 CDI's higher power output puts slightly more stress on the chain than the B200 CDI. Mercedes has revised the tensioner multiple times. Parts for the full chain kit cost 200-400, but labor is substantial as the engine may need to be partially lifted. Total replacement cost is 1,000-2,000 at an independent specialist. Ignoring the rattle risks chain skip and catastrophic valve damage. Regular oil changes at 10,000-15,000 km intervals (rather than the factory 25,000 km) significantly extend chain life.

The exhaust gas recirculation system on the OM651 accumulates carbon deposits over time, particularly on cars driven gently or on short trips. Symptoms include rough idle, hesitation during acceleration, black smoke, and reduced power. Cleaning the valve costs 150-250. If the valve motor has failed, replacement costs 350-500. The EGR cooler can also develop internal leaks, allowing coolant into the intake tract, which causes white smoke on cold starts and gradual coolant loss. EGR cooler replacement costs 400-900 including labor. Mercedes released an updated cooler design to address the internal leak issue. Regular motorway driving of at least 30 minutes per week and quality diesel fuel help reduce carbon buildup.

The OM651 fuel filter housing has coolant passages running through it and bolts to both the cylinder head and inlet manifold. Under boost pressure, the inlet manifold flexes, stressing the housing seals. This causes a slow coolant leak that can be difficult to pinpoint as it often drips internally rather than pooling visibly. Symptoms include gradually dropping coolant level with no obvious external leak, and sometimes a sweet smell from the engine bay. Mercedes released an updated housing design (part A6512003900). The replacement part costs 80-150, but the repair requires removing the EGR cooler and replacing its gasket as well, bringing total repair to 250-500 at an independent shop. This is one of the most common OM651 faults across the entire Mercedes range.

Euro 6 variants of the B220 CDI/B220d (primarily from 2015 onwards) use an AdBlue (SCR) system with NOx sensors. The upstream NOx sensor is prone to failure from water ingress and corrosion caused by condensation in the exhaust. Symptoms include AdBlue warning messages, engine management light, and eventually a countdown to a no-start condition. An OEM sensor costs 300-500, with labor of 100-200 for replacement. Mercedes addressed this with a revised sensor design that includes a drain hole. Some dealers replaced under goodwill on cars less than 5 years old, but most W246 models are now outside this window. Pre-2015 Euro 5 models do not have AdBlue and are unaffected.

Early OM651 engines (2012-2013 production) used Delphi piezo injectors that were sensitive to fuel quality and prone to erratic fuel delivery. Mercedes issued a service campaign to replace these with updated solenoid-type injectors. The changeover happened in production from mid-2012. Most B220 CDI models from 2013 onwards should already have solenoid injectors, but verify this before purchase. A single remanufactured injector costs 200-350, with programming required via Star diagnostic. Replacing all four injectors costs 800-2,000 depending on whether remanufactured or new units are used.

Several W246 owners report the electronic parking brake becoming stuck or displaying a malfunction warning on the dashboard. The issue can be caused by a faulty actuator motor, corroded cables, or a software glitch in the control module. In some cases, holding the parking brake switch for 10+ seconds and restarting the engine resolves the problem. When the actuator itself needs replacement, costs run 300-700 including parts and labor. The issue is more common on cars that have had little use or have been stored for extended periods.