Mercedes-Benz S 320
Three-valve V6 with individual ignition coils. Smooth and strong. Typical weak points: crankcase breather and intake manifold flaps. High mileages achievable.
Solid Base
165 kW — adequately powered for everyday use, without excitement.
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 6
The Airmatic compressor runs continuously when there are leaks in the system and burns out. Without swift intervention, total suspension failure and blocked ride-height control follow.
Air spring bag seals age and become leaky. The vehicle drops on one side or completely. All four struts typically need replacement by around 250,000 km.
Three SAM modules in the engine bay and interior are vulnerable to water ingress through blocked drain channels. Secondary damage can exceed the vehicle's residual value.
The hollow-section sills of the W220 rust from the inside out. Nothing is visible externally for a long time until the rust is already well advanced. Pre-facelift models (1998–2002) are particularly affected.
The W220 rusts at the underbody, wheel arches and weld seams, particularly where underbody protection has not been renewed regularly.
Electric window regulators are not rated for the weight of the W220 double-glazed windows and wear out prematurely. Driver's side particularly affected.
Reports & Tests
289 owner complaints filed with NHTSA (1998–2005). Most reported: Electrical (108), Suspension (68), Lighting (24).