Mercedes-Benz ML 250 BlueTEC

Over 100,000 vehicles recalled: the chain tensioner seal leaks, allowing engine oil to drip onto the exhaust system and potentially ignite.

Symptoms: Dropping oil level, oil smell from engine bay, oily deposits under the vehicle, possible oil fire

The OM651 uses a simplex timing chain. With short-trip driving and overdue oil change intervals the chain stretches.

Symptoms: Light rattling noise on cold start from the rear of the engine, no fault code stored

Same Delphi piezo injector problems as in the DE18: 220 CDI and 250 CDI variants affected. Mercedes replaced them with solenoid injectors as part of a service action.

Symptoms: Vibrations and rough running especially under acceleration, elevated fuel consumption

The EGR cooler of the OM651 develops hairline cracks at the connection stub and loses coolant. Green staining next to the fuel filter under the engine cover is typical.

Symptoms: Dropping coolant level without visible leak, intermittent coolant warning, green spots under the vehicle, heater output diminishing

The DMF on the OM651 suffers under the high torque output. Documented case: all 8mm rivets sheared at 149,000 km, with consequential damage to the clutch and crankshaft speed sensor.

Symptoms: Rattling and juddering at warm idle, vibrations when pulling away, shuddering at low RPM, noise increases with warm engine

From around 150,000–180,000 km the OM651 turbocharger leaks oil through worn bearings, which drips onto the EKAS intake port deactivation actuator and destroys it. Double damage.

Symptoms: Black smoke under acceleration, oil residue in charge air hose, power loss, fault code P0299 boost pressure underrun

The optional AIRMATIC suffers from porous air bags at higher mileages. The compressor pumps continuously and eventually burns out.

Aluminium steering rack bolts corrode due to road salt. If all three bolts fracture, power steering fails completely. KBA recall 012425.

AIRMATIC compressor frequently fails from 80,000 km onward, vehicle sags or shows persistent fault messages. Repair at a Mercedes workshop is very costly.

On diesel variants, sensors incorrectly report low AdBlue level despite a full tank. Crystallised AdBlue and defective NOx sensors cause costly repairs.