OM651 engine: faults and reliability

• OM651 1.8 CDI 109-136 hp (180/200 CDI)

  2011–2018 · 109–136 hp

  With caution

  It shares the general risks of the OM651 family (timing chain, EGR and particulate filter), but no injector failure pattern specific to this lower-output variant is documented. Before buying, verify the engine code stamped on the block, because the same commercial name can correspond to a different, Renault-built engine.^[2][8]

• OM651 2.2 CDI 120-190 hp (200/220 CDI, 114-119 CDI)

  2008–2019 · 120–190 hp · OM651.911, OM651.924, OM651.930, OM651.940

  With caution

  It is the best-documented variant and, overall, reasonably reliable, but units built before 2011 (220 CDI) may still have piezo injectors, and those built before 2014 do not have the revised chain tensioner. Check whether the manufacturer's campaigns have been carried out, and the condition of the chain, before buying.^[2][3][9]

• OM651 2.2 CDI twin-turbo 204 hp (250 CDI / 250d / 250 BlueTEC)

  2009–2019 · 204 hp

  With caution

  It is the version with the highest risk of injector failure, because it kept the Delphi piezo injectors throughout its production according to the available source. There is, however, no single reliable way to confirm this other than a return-flow test or the injector replacement history, so it stops short of being advised against in general.^[2]

Buy: No known serious faults, or they have already been corrected, in this version. With caution: Worth buying if something specific is verified: history, a replaced part or a completed campaign. Avoid: High risk of a serious fault that is hard to check for or prevent.

1. 1Critical severityVery frequentFrequency: Very frequentTimingTiming chain stretch and tensioner failureYes: the OM651 timing chain can stretch prematurely, above all on units built up to 2013, and in 2014-2015 Mercedes-Benz recalled around 114,000 vehicles in Germany over a defective sealing ring in the tensioner. A metallic rattle on a cold start is the first sign.Repair (garage): €2,000–€3,500Appears at around 120,000 km
2. 2High severityVery frequentFrequency: Very frequentInjectionDelphi piezo injector failure (220/250 CDI)Yes: 220 and 250 CDI models built between 2008 and 2011 had Delphi piezo injectors that were prone to failing and seizing in the cylinder head. Mercedes-Benz replaced them under warranty in 2009 and switched the 220 CDI to solenoid injectors from 2010-2011, but the 250 CDI kept them.Repair (garage): €3,600–€5,900
3. 3High severityVery frequentFrequency: Very frequentEmissions controlEGR and particulate filter clogging, and emissions software updatesThe particulate filter and EGR clog up with short journeys, as on any diesel with these systems. In addition, Germany's KBA required software updates on several models with this engine between 2018 and 2021 because of a function that reduced EGR outside a temperature range.Repair (garage): €800–€2,500
4. 4High severityCommonFrequency: CommonTurboVariable-geometry turbo failure and its pneumatic actuatorThe OM651's variable-geometry turbo tends to fail at the pneumatic actuator (cracks, loss of calibration) before the turbo itself. Symptoms range from a gradual loss of power to permanent limp mode, with whistling or smoke if the problem progresses.Repair (garage): €500–€3,000
5. 5Medium severityCommonFrequency: CommonCoolingCoolant leak from the thermostat connector and heat exchangerYes: the thermostat connector or housing on the cylinder head, and the oil-water heat exchanger, are common coolant leak points on the OM651. Mercedes-Benz even had a specific service action for the cylinder head connector.
6. 6Medium severityCommonFrequency: CommonInjectionInjector seal leak and carbon build-up around the seat ("black death")The copper washer that seals each injector can start letting combustion gases past and form a crust of carbon around the injector, known as "black death". Caught in time, it is fixed with a new washer; if left, the injector can end up seized in the cylinder head.

Severity colours: low, medium, high, critical. How we rate them

Manufacturer

Mercedes-Benz (Daimler)

Family

OM651

Fuel

Diesel

Displacement

2,143 cm³

Cylinders

4

Fuel system

Turbo

Injection

Common rail

Timing

Chain

Power

95–204 hp

Peak torque

500 Nm

Production

2008–2019

Makes

Mercedes-Benz and Infiniti

Technical data^{[1][3][5][6][7]}

1. 2008–2019

   OM651 2.2 CDI 120-190 hp (200/220 CDI, 114-119 CDI)

   The 2.2-litre block (2,143 cc) with a single variable-geometry turbo, used in most "200 CDI" and "220 CDI" cars and in the 114, 116 and 119 CDI van trims. The 200 CDI had Delphi solenoid injectors from the start; the 220 CDI used piezo injectors until Mercedes-Benz replaced them with solenoid ones between mid-2010 and spring 2011. From 2014 the timing chain tensioner was revised following a recall campaign.^[2][7][9]

2. 2009–2019

   OM651 2.2 CDI twin-turbo 204 hp (250 CDI / 250d / 250 BlueTEC)

   The most powerful version of the 2.2-litre block, with a second turbo stage (sequential twin-turbo) to reach 204 hp and 500 Nm. According to the source consulted, Mercedes-Benz never replaced the Delphi piezo injectors on the 250 CDI with the solenoid ones that did reach the 220 CDI, so the risk of injector failure persists on units of any year.^[2][3]

3. 2011–2018

   OM651 1.8 CDI 109-136 hp (180/200 CDI)

   The smaller-capacity variant (1,796 cc) developed by Mercedes-Benz for the front-wheel-drive A-Class and B-Class, with 109 and 136 hp. Be careful when buying: on the A-Class, the "180 CDI" badge can mean this Mercedes engine (in the automatic, until January 2014) or a Renault-sourced 1.5 dCi (OM607) that has powered every 180 CDI since that date; check the engine code and do not rely on the commercial name alone.^[8][14]