Mercedes-Benz B 180 CDI
Smaller displacement variant of the OM651. Same technology as the 2.1L but less torque. Known for injector seal issues and timing chain stretch.
B-Class CDI Base
80 kW OM651 in the van: more refined than the competition, but too weak for real comfort with a load.
Engine Weaknesses 5
Quality issues with Delphi piezo injectors in the 220 CDI and 250 CDI: injectors fail prematurely. A service action replaced piezo injectors with solenoid injectors free of charge.
Symptoms: Strong vibrations under acceleration, rough running, elevated fuel consumption, exhaust smoke
The OM651 chain tensioner can fail and allow engine oil to escape. Mainly affects vehicles built February–November 2014 (recall). Simplex roller chain increases wear risk.
Symptoms: Light rattling on cold start from the rear of the engine, oil loss, engine warning light
The DPF on the OM651DE18 does not regenerate completely during pure short-trip driving and blocks. A motorway run at least every 2 weeks is required.
Symptoms: DPF warning light, power reduction, engine oil diluted by unburnt fuel
The O-rings on the oil filter housing and oil cooler of the OM651 shrink and develop leaks. Oil seeps out on the side of the engine. Requires removal of the poly-V belt and AC compressor.
Symptoms: Oil spots under the engine, dropping oil level without visible leak, oil smell after driving
The OM651 EGR valve tends to heavy carbonisation on short trips, causing power loss and increased emissions.
Symptoms: Power loss, limp mode, black smoke, EGR fault code, rough idle
Vehicle Weaknesses 5
Collision warning system incorrectly detects obstacles in urban traffic and initiates autonomous emergency braking. Software update resolves the problem. Rear light failures also known.
Corroded connectors on the ECU cause failure of ESP, ABS and PRE-Safe. Safety systems are deactivated, vehicle goes into limp mode.
Door lower edges of the W246 rust, though less severely than the predecessor. Axle springs and components corrode and can break through oxidation. Rust susceptibility inappropriate for the price level.
A/C condensers can develop leaks and lose refrigerant. A/C cooling diminishes after several years. Problem less frequent than on the predecessor W245 but still present.
Brake discs and brake hoses wear above average on the W246. MOT reports flag this regularly. Brake lines on older examples are prone to corrosion.