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.
CLK V6: Class and Character
160 kW V6 M112 in the CLK C208 — this is the right engine choice. Silky V6 sound, refined power, elegant coupé/cabriolet. A genuine Mercedes moment.
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
Design flaw: vibrating trim strips grind away the paint and allow rust to form. Front and rear wheel arches, lower door edges, boot lock area and bumper transitions particularly affected.
Valeo transmission oil cooler develops a leak, coolant enters the automatic transmission and destroys the multi-plate clutches. Affects vehicles up to model year 2003. Transmission replacement usually required.
Control arm bushings, tie rod ends and camber struts wear out as mileage increases. Steering becomes imprecise and susceptible to road ruts. Replacements regularly flagged at MOT.
Airbag control units fail and trigger warning lights. Xenon headlight control units fail at a cost of over 1,000 euros per headlight. Wiring harness hardens with age.
The electronic ignition lock increasingly fails to recognise the key reliably with age, the steering lock does not release or the engine does not start. Vehicles from around 150,000 km particularly affected.