1.8 / 2.1 CDI (OM651)
2011–2018 · diesel · 2143cc · 136hp
Engine codes: OM607, OM651
Reliability, common problems and owner reviews for the Mercedes Benz B-Class 1.8 / 2.1 CDI (OM651). Check this before you buy used.
The OM651 (B180/B200/B220 CDI) is Mercedes' workhorse four-cylinder diesel — strong, economical and high-mileage capable, the same engine used across C/E-Class. Two well-known watch items: early cars used Delphi injectors that could fail (later Bosch were better), and the timing chain (mounted at the back of the engine) can rattle/wear, which is a labour-heavy job. Plus the usual DPF/EGR on short trips. A documented, motorway-driven example with good injectors is a dependable long-hauler.
Same engine, other cars
This is the same physical engine (OM607) sold under different names across brands. Reliability is broadly shared — cross-check these:
Known Issues
Early OM651 Delphi injectors can fail → rough running, smoke, hard start; later Bosch improved.
Fix / Workaround: Injector test; replace failed (ideally with revised parts).
Repair cost: €250–€1200
Typically appears after: 120,000 km
Chain/tensioner wear causes rattle; rear-of-engine location makes it labour-heavy.
Fix / Workaround: Strict oil; replace chain kit at rattle.
Repair cost: €600–€1600
Typically appears after: 150,000 km
DPF clogs and EGR soots on urban use.
Fix / Workaround: Motorway regens; clean/replace.
Repair cost: €300–€1100
Early OM651 Delphi injectors can fail; rear-mounted chain can rattle (labour-heavy).
Fix / Workaround: Injector test; chain rattle check; revised parts.
Repair cost: €250–€1600
Typically appears after: 130,000 km
Renault-sourced OM607 has the usual injector/EGR/DPF cautions on short trips.
Fix / Workaround: Motorway regens; injector/EGR service.
Repair cost: €200–€1000
Typically appears after: 130,000 km
Mileage Thresholds
After 150,000 km: Injector + chain window.
Pre-Purchase Checklist
- ☐Injector history (early Delphi vs later)
- ☐Cold-start chain rattle check
- ☐DPF history (city cars)
- ☐OM651: injector + chain history
- ☐OM607 is the smaller Renault-derived 1.5
Frequently asked questions
Is the Mercedes Benz B-Class 1.8 / 2.1 CDI (OM651) reliable?
Maint. Sensitive — The OM651 (B180/B200/B220 CDI) is Mercedes' workhorse four-cylinder diesel — strong, economical and high-mileage capable, the same engine used across C/E-Class. Two well-known watch items: early cars used Delphi injectors that could fail (later Bosch were better), and the timing chain (mounted at the back of the engine) can rattle/wear, which is a labour-heavy job. Plus the usual DPF/EGR on short trips. A documented, motorway-driven example with good injectors is a dependable long-hauler.
What are the common problems and reviews for the Mercedes Benz B-Class 1.8 / 2.1 CDI (OM651)?
The most commonly reported problems: Injector failure (early Delphi), Timing chain wear (rear-mounted), DPF / EGR (short trips), OM651 injector (early Delphi) / chain, DPF / EGR / injectors (OM607).
Is a used Mercedes Benz B-Class 1.8 / 2.1 CDI (OM651) worth buying?
Fine if serviced correctly — but it punishes neglect hard. History and the right consumables matter.