Diesel · 2007–2014
Enter your VIN and mileage and get a plan built for your exact engine and gearbox.
All about the Mercedes-Benz C-Class (W204)All about the 1.8 / 2.1 CDI (Mercedes OM651) engine
The 2.1 CDI (Mercedes OM651) engine was fitted to the Mercedes-Benz C-Class (W204) (2007–2014). In the EU that is 33.2 % of all new cars of this generation.
Versions: 2.1, 2.1 170 hp, 2.1 136 hp, 2.1 120 hp, 2.1 204 hp.
The most expensive known risk is timing chain stretch or tensioner wear (single-row chain at the rear): it usually appears at 120,000–250,000 km and costs €300–2,500 to fix.
✓ The faults of this engine were checked against sources (10/2026). Each item has at least two independent sources or an official recall or parts-maker technical note.
Signs: Engine light, limp mode, rough running and jerking, hard starting, smoke
Fix: Have a dealer check by VIN whether the conversion to solenoid injectors (new ECU software, return line) was done; otherwise test and replace the faulty piezo injectors
Signs: Harder starting, rough idle, knocking, smoke, diesel smell or soot around an injector
Fix: Return-flow test and check of the quantity correction values to find the weak injector; replace that injector or its seal rather than the whole set
Signs: Rattle for a few seconds after a cold start, later constant; P0016 / P0017, power loss
Fix: Read the cam-crank phase offset and measure chain stretch; fit the revised tensioner if the chain is in tolerance, otherwise replace chain, sprocket, tensioner and guides
Signs: Usually none before failure; oil seepage at the tensioner, in extreme cases the tensioner loosens and the chain can jump
Fix: Have a dealer check by VIN that the free seal ring replacement was done (about 1.5-2.5 h); also applies to older cars that got a tensioner from that period
Signs: Falling coolant level, traces near the intake manifold or fuel filter, temperature warning
Fix: Pressure-test the system; replace the coolant flange with the reinforced version (EGR cooler must come off) or the water pump; ask the dealer about service action 1204P59A93
Signs: Oil on the front of the engine and under the car, oil smell; rarely oil and coolant mixing
Fix: Find the exact leak (oil cooler check valve O-ring, transfer pipe seals or the cooler itself) and replace the seals or the oil cooler
Signs: Slight to clear power loss, P0401 (low EGR flow), rough idle, black smoke; a cracked cooler loses coolant into the intake
Fix: Compare EGR target and actual position in live data; clean the valve thoroughly or replace it, and the cooler if it is blocked or leaks
Signs: DPF warning, frequent or interrupted regenerations, limp mode
Fix: Check the pressure sensor and soot load first and fix any EGR or injector fault; forced regeneration, cleaning or replacement; use MB 229.51 / 229.52 low-ash oil
Signs: Engine light with boost pressure or flap codes (e.g. P200A), power loss, rough idle
Fix: Smoke-test the intake for cracks and check the flap motor; replace the manifold with a new flap motor (coolant must be drained)
Signs: No symptoms; an open recall can lead to registration problems, some owners report slightly higher fuel use after it
Fix: Have a dealer check by VIN that the free software update was done
Signs: Key turns but the ignition does not come on and the wheel stays locked; at first only now and then, often in cold weather.
Fix: Diagnose ELV vs ignition switch (EZS); a specialist replaces the ELV actuator motor, or a new ELV is fitted and activated online by Mercedes-level diagnostics.
Signs: Heavy scaling or holes on the rear subframe, often missed because it rots from inside; failed inspection, in the worst case a cracked mount.
Fix: Inspect the rear axle carrier on a lift before buying; replace it (ask Mercedes about goodwill) and protect the new one with cavity wax.
Signs: Knocking or rumbling from the front over bumps, vague steering, worn axle mountings flagged at inspection.
Fix: Check dampers, top mounts, control arms and drop links; replace worn parts in pairs and set the alignment.
Signs: Corroded brake pipes under the car, parking brake holds poorly or not at all on the test.
Fix: Replace corroded brake lines; free up or renew the parking brake shoes and cables and use the parking brake regularly.
Signs: Airbag warning light possible; airbags may not deploy in a crash or may deploy without one.
Fix: Check the VIN; the dealer replaces the SRS control unit free of charge.
Signs: Slipping, high bite point
Fix: Replace clutch kit
Signs: Rattle at idle, vibration pulling away
Fix: Replace with clutch
Signs: Holds a gear too long then shifts hard, sticks in gear or limp mode, converter lock-up stops working; codes 0717 / 0718 / 0722 / 2201
Fix: Confirm with Mercedes-level diagnostics; replace or rebuild the conductor plate (with the valve body on early VGS1 units), change the fluid with the correct MB spec and code / adapt the unit
Signs: Harsh shifts when warm, drops from D to N at stops, starts in 3rd, reverse will not engage, 'F' on the dash; codes P073E00, P07B700
Fix: Read the codes and fluid condition; repair / rebuild the mechatronic (pressure sensors) or replace it, then change the fluid and run the adaptations
Signs: Oil around the gearbox plug, oil found inside the wiring harness or control-unit plug, intermittent gearbox faults
Fix: Replace the connector adapter and its O-rings, clean the oil out of the harness and plugs; disconnect only with gearbox oil below 50 C
Typical routine maintenance cost for 100,000 km: €2,400–5,750. Sum of the services and wear parts in the plan above (about 15,000 km a year, independent workshop), without faults.
Intervals and typical prices for the Mercedes-Benz C-Class (W204) with the 2.1 CDI (Mercedes OM651) engine. The app gives the exact plan for your mileage.
| Item | Interval | Typical price |
|---|---|---|
| DPF health check (soot / ash load)Emissions | every 20,000 km | €0–60 |
| Engine oil + oil filterEngine | every 15,000 km or every 12 months | €70–150 |
| Cabin (pollen) filterClimate | every 15,000 km or every 12 months | €15–40 |
| Brake fluidBrakes | every 24 months | €50–95 |
| A/C service (regas + desiccant)Climate | every 24 months | €70–150 |
| Air filterEngine | every 30,000 km or every 24 months | €15–45 |
| Fuel filterFuel | every 30,000 km or every 24 months | €40–110 |
| Glow plugsEngine | every 100,000 km | €120–300 |
| Auxiliary (serpentine) beltEngine | every 120,000 km | €70–180 |
| Coolant replacementCooling | every 150,000 km or every 96 months | €70–150 |
| Timing chain inspection (listen on cold start)Engine | every 150,000 km | €0–120 |
| Manual gearbox oilTransmission | every 150,000 km | €60–130 |
| Front brake padsBrakes | usually at 30,000–60,000 km | €60–150 |
| Front brake discs + padsBrakes | usually at 60,000–120,000 km | €150–320 |
| Rear brake padsBrakes | usually at 50,000–90,000 km | €50–130 |
| Tyres (set of 4)Wheels | usually at 40,000–60,000 km | €320–700 |
| Wiper bladesBody | checked at service | €20–50 |
| 12V batteryElectrical | checked at service | €100–220 |
| Version | Share | Years | CO₂ | Fuel use |
|---|---|---|---|---|
| 2.1 Diesel2,143 cm³ | 37.7 % | 2010–2013 | — | — |
| 2.1 Diesel2,143 cm³ · 125 kW (170 hp) | 10.6 % | 2011–2013 | — | — |
| 2.1 Diesel2,143 cm³ · 100 kW (136 hp) | 7.6 % | 2011–2013 | — | — |
| 2.1 Diesel2,143 cm³ · 88 kW (120 hp) | 4.5 % | 2011–2013 | — | — |
| 2.1 Diesel2,143 cm³ · 150 kW (204 hp) | 2.6 % | 2011–2013 | — | — |
Source: European Environment Agency (EEA), monitoring of CO₂ emissions from new passenger cars, CC BY 4.0. CO₂ and fuel use are official type-approval values (WLTP from 2021), not real-world consumption.
Recalls the manufacturer published in the United Kingdom for this model (53). The same recalls usually apply across Europe. Ask an authorised dealer to check by VIN whether your car is affected and whether the work has been done.
The faults with the highest risk: timing chain stretch or tensioner wear (single-row chain at the rear) (120,000–250,000 km, €300–2,500); rear axle carrier rusts from the inside (80,000–300,000 km, €700–2,000); electronic steering lock (ELV) fails, car will not start (80,000–300,000 km, €250–1,200); DPF clogging (mostly short trips) (80,000–200,000 km, €150–1,800).
Chain.
5W-30 · MB 229.51 / 229.52 · ~6.5 L · every 15,000 km.
1.6 / 1.8 Kompressor / CGI (Mercedes M271)2.2 CDI (Mercedes OM646)3.0 CDI V6 (Mercedes OM642)2.5 / 3.0 / 3.5 V6 & V8 (Mercedes M272 / M273)
Mercedes-Benz C-Class (W205) 2014–2021Mercedes-Benz E-Class (W212) 2009–2016Mercedes-Benz A-Class (W176) 2012–2018Mercedes-Benz GLC (X253) 2015–2022Mercedes-Benz CLA (C117) 2013–2019Mercedes-Benz GLA (X156) 2013–2020Mercedes-Benz B-Class (W246) 2011–2018Mercedes-Benz Vito (W447) 2014–Mercedes-Benz ML / GLE (W166) 2011–2019Mercedes-Benz GLK (X204) 2008–2015Mercedes-Benz SLK / SLC (R172) 2011–2020Mercedes-Benz CLS (C218) 2011–2018
Main sources for the faults of this engine:
Faults, intervals and prices are indicative and collected from public sources and owner experience; always rely on the service book and a qualified workshop. Test statistics: DVSA – Anonymised MOT tests and results, Open Government Licence v3.0. Dutch tests: RDW Open Data (CC0). Engine versions: EEA, monitoring of CO₂ emissions from new passenger cars (CC BY 4.0, DG CLIMA). Owner complaints: NHTSA ODI (public domain). Recalls: DVSA Vehicle Safety Branch Recalls Database, OGL v3.0. Brand and model names are trademarks of their owners and are used only to describe the vehicles. How we check the data →
Updated 29/10/2026