220/250 CDI 2.1 (OM651)
2008–2015 · diesel · 2143cc · 204hp
Engine codes: OM651
Reliability, common problems and owner reviews for the Mercedes Benz GLK 220/250 CDI 2.1 (OM651). Check this before you buy used.
The ML250's twin-turbo 2.1 four-cylinder (OM651) is impressively economical for a car this size and surprisingly capable — but it's a small diesel working hard in a big SUV. Same OM651 watch-list as the saloons: early Delphi injectors that could fail (later Bosch better), the rear-mounted timing chain that can rattle/wear (labour-heavy), and DPF/EGR on short trips. A documented, motorway-driven example is dependable and very frugal; some buyers still prefer the effortless V6.
Same engine, other cars
This is the same physical engine (OM651) sold under different names across brands. Reliability is broadly shared — cross-check these:
Known Issues
Early OM651 Delphi injectors can fail → rough running, smoke; later Bosch improved.
Fix / Workaround: Injector test; replace with revised parts.
Repair cost: €250–€1200
Typically appears after: 120,000 km
Rear-mounted chain/tensioner wear → rattle; labour-heavy.
Fix / Workaround: Strict oil; replace chain kit at rattle.
Repair cost: €600–€1600
Typically appears after: 150,000 km
DPF and EGR on short urban use.
Fix / Workaround: Motorway regens; clean/replace.
Repair cost: €300–€1100
DPF and EGR on short trips.
Fix / Workaround: Motorway regens; clean/replace.
Repair cost: €300–€1100
Mileage Thresholds
After 150,000 km: Injector + chain window.
Pre-Purchase Checklist
- ☐Injector history (Delphi vs Bosch)
- ☐Cold-start chain rattle check
- ☐DPF history (city cars)
- ☐Frugal but works hard — V6 is effortless
Frequently asked questions
Is the Mercedes Benz GLK 220/250 CDI 2.1 (OM651) reliable?
Maint. Sensitive — The ML250's twin-turbo 2.1 four-cylinder (OM651) is impressively economical for a car this size and surprisingly capable — but it's a small diesel working hard in a big SUV. Same OM651 watch-list as the saloons: early Delphi injectors that could fail (later Bosch better), the rear-mounted timing chain that can rattle/wear (labour-heavy), and DPF/EGR on short trips. A documented, motorway-driven example is dependable and very frugal; some buyers still prefer the effortless V6.
What are the common problems and reviews for the Mercedes Benz GLK 220/250 CDI 2.1 (OM651)?
The most commonly reported problems: Injector failure (early Delphi), Timing chain wear (rear), DPF / EGR (short trips), DPF / EGR.
Is a used Mercedes Benz GLK 220/250 CDI 2.1 (OM651) worth buying?
Fine if serviced correctly — but it punishes neglect hard. History and the right consumables matter.