Mercedes-Benz M-Klasse 166 ML 250 BlueTEC, 204 PS, 7-speed automatic, all-wheel drive (2011–2015)

Research for this car

• Generation guide Mercedes M-Class W166 (2011-2015): known problems and buying guide

  Average reliability. On the V6 diesel check the AdBlue system, intake flaps and oil cooler seals, and give Airmatic cars a pressure test.

• Engine guide Mercedes OM651 2.1 diesel (C 220 CDI, E 250 CDI, Sprinter): problems, costs and what to check

  Durable when maintained, but check the cold start chain rattle, early injectors and the 2014 tensioner seal before you buy.

• Gearbox guide Mercedes 7G-Tronic (722.9) 7-speed automatic: problems, costs and what to check

  Buy only with fluid records and a clean full-system scan, and avoid any car that has run in limp mode or judders at a steady speed.

Known issues for this car

Before you buy this car

From the generation guide

1. Run the Airmatic pressure test with a scanner: a 30-minute pressure hold. A drop under 0.3 bar is fine. Bad result: a bigger drop, a sag after parking, or a compressor that runs for more than 30 seconds per cycle. Needs a scanner.
2. Ask a Mercedes dealer to check the VIN for open campaigns. Bad result: an open campaign, for example the steering gear bolts or the water ingress at the fuel pump control unit.

From the engine guide

1. Timing chain (scanner needed). Start the engine cold and listen for a metallic rattle for 1-3 seconds. Ask a Mercedes dealer or a diesel specialist to read the cam phase offset (the timing gap between camshaft and crankshaft) with XENTRY, the Mercedes diagnostic tool. Check for codes P0016 and P0017. A plain OBD2 scanner may miss the offset. Bad: a rattle, a stored P0016 or P0017, or a large offset. A jumped chain can destroy the engine.
2. Coolant (no scanner). Check the coolant level when the engine is cold, and check it again after a few weeks. Ask a dealer whether service action 1204P59A93 was done on the cylinder head coolant connection. Bad: a falling level or no record of the work.
3. Tensioner seal recall (VIN check). For cars built February to November 2014, ask a Mercedes dealer to check the VIN for the seal ring fix. Bad: no record of the fix.
4. Emissions software update (VIN check). Ask a Mercedes dealer to check the VIN for the emissions software update. Bad: no record of the update.
5. Oil and service history (no scanner). Ask for oil change records. Long gaps between oil changes, short trips and poor oil all speed up chain wear. Bad: long gaps or no records.

From the gearbox guide

1. Read the shift pressure data with XENTRY or an equal Mercedes scanner. Bad result: pressure deviations above 0.5 bar, or adaptation values above 30 percent. Those point to valve body wear.
2. Read the full gearbox fault memory with a full-system scanner. An engine-only OBD2 reader does not show it. Bad result: speed sensor codes P0717, P0718, P0722 or P0793, or any stored limp mode.
3. Test drive cold and warm, and pull away from a stop. Bad result: stuck in 2nd, slipping between 1st and 2nd, or limp mode at about 48 km/h (30 mph).
4. Hold a steady light throttle at about 60 km/h. Bad result: a shudder or hum. A scanner shows converter slip; 5 to 25 rpm is normal, and above about 80 rpm points to clutch wear.
5. Ask for the fluid invoices and check the fluid. Bad result: no change after about 80,000 km, dark brown or black fluid, a burnt smell, or a fluid other than the one for the build. A wrong fluid can cause code P0741. Red-amber is the correct colour.
6. Ask a dealer whether bulletin LI27.20-P-055758 applies to the car's VIN, and whether it was done. Bad result: lock-up codes FC 2783 or FC 0741 still stored.

Running costs

ADAC figures for 15,000 km a year over 60 months

ADAC versions