Mercedes-Benz CLK 320
Three-valve V6 with individual ignition coils. Smooth and strong. Typical weak points: crankcase breather and intake manifold flaps. High mileages achievable.
V6 Elegance in the New CLK
160 kW V6 M112 in the CLK C209 — the engine harmonises perfectly with the coupé character. Refined, powerful, no-drama engine.
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 5
Valeo transmission oil heat exchanger on pre-facelift models up to 09/2003 develops leaks. Coolant enters the transmission and destroys the clutch packs. Symptom: humming and juddering at low revs.
Xenon headlight control modules and burners fail regularly after 1–2 years of operation. Third brake light breaks and fails frequently. Number plate lighting contacts corrode.
Brake caliper brackets corrode and cause rattling and squealing. Rear brake lines become brittle with age. Handbrake seizes when not used regularly.
COMMAND navigation system freezes or fails to start. Parktronic ultrasonic sensors fail regularly. CD changer jams. Seat belt retractor sticks.
The frameless side window drops when the door opens and rises when it closes. In frost the mechanism freezes; the door control module keeps trying to lower it — clicking in the module, flickering interior lighting.