Mercedes-Benz ML 350
Three-valve V6 with individual ignition coils. Smooth and strong. Typical weak points: crankcase breather and intake manifold flaps. High mileages achievable.
Adequately Powered
173 kW in the SUV is adequate for everyday use. Not exciting, but not underpowered either.
Engine Weaknesses 7
The camshaft adjuster solenoid on the M112 develops a leak and draws oil by capillary action into the wiring harness. Oil can migrate as far as the engine ECU and destroy it.
Symptoms: Cold-start rattling that disappears after 1–2 seconds, camshaft adjuster fault code, oil traces at wiring connector, later ECU faults
The vacuum hose for the variable intake manifold on the M112 becomes brittle and breaks. The swirl flaps stick. The hose is not available individually — the entire intake manifold is needed.
Symptoms: Power drop, slight hesitation at part throttle, engine runs but without full power
On the M112 V6 the valve cover gaskets become porous over time. Especially the rubber seals on the front cover between the timing cover and engine block fail on virtually all high-mileage M112 engines.
Symptoms: Oil spots on the floor, oil smell after driving, oily engine bay, dropping oil level
The plastic linkage of the variable intake manifold in the M112 typically breaks around 150,000 km. The actuator and tumble flaps freeze in one position — according to forum reports, all M112 engines are eventually affected.
Symptoms: Engine enters limp mode, power drop at higher revs, intake flap fault code, stumbling on acceleration
The M112 V6 has two spark plugs per cylinder sharing a dual-output ignition coil. Neglected plugs prematurely destroy the coils.
Symptoms: Rough idle, individual cylinder misfires, CEL, power loss at cold start
The crankcase ventilation membrane in the M112 wears and causes elevated oil consumption and engine sweating. Engine power can also drop due to false air ingestion.
Symptoms: Oil consumption above 1 L/5,000 km, light oil mist in engine bay, smoke from exhaust
The thermostat on the M112 V6 can stick in the open position. Engine only reaches 70–80°C instead of the target 87°C. Result: increased fuel consumption, poor heater output.
Symptoms: Engine doesn't warm up properly, heater stays cold, increased fuel consumption, temperature gauge permanently low
Vehicle Weaknesses 7
The US-built W163 received insufficient corrosion protection from the factory. Boot lid, sills, wheel arches and bonnet are particularly susceptible.
The wiring harness at the ABS hydraulic block chafes against the wheel arch liner and causes ABS and ETS failures. A known design fault.
Brake lines are known to corrode through. Complete replacement requires removal of the rear axle, driveshaft and fuel tank. A safety-critical problem.
The automatic transmission suffers premature torque converter wear, particularly on the ML 400 CDI and with frequent trailer use.
The transfer case chain stretches from around 100,000 km and can jump. Noises on pull-away are an early warning. In the worst case, total drivetrain failure.
Ladder frame rusts heavily, particularly at the rear and at longitudinal member sections. Suspension mounting points can be so weakened by corrosion that the vehicle's roadworthiness is at risk.
Cables in the tailgate transition break through constant opening and closing. Rear screen wiper, third brake light and number plate lighting are affected.