Mercedes-Benz SL 350

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 ABC hydraulic pump can develop cracks and lose pressure from 120 bar down to 60 bar. Suspension can no longer maintain ride height, soft and vague handling characteristics.

The hydraulic fluid absorbs moisture, rubber components decompose and contaminate the system. Valve block and lines develop leaks. Annual oil change prevents major damage.

The SBC unit is designed for approximately 400,000 brake cycles and fails at this point. When it fails, braking effectiveness is severely reduced — a safety risk. Mercedes extended the warranty to 25 years.

The electric motor of the roof pump burns out. Windings and circuit board affected. Pump runs audibly for longer or not at all. Specialist repair from 595 EUR, Mercedes dealer significantly more expensive.

Defective control unit causes functional failures of the vario roof. Roof stops in various positions, headrests raise but do not return.

The electric folding roof develops problems with limit switches and hydraulic components. When the sequence is disrupted, the roof no longer opens or closes.

The R230 develops clicking and creaking noises in the steering rack, often at every third steering input or under load. Track rod ends are a frequent cause. The steering rack can also lose hydraulic oil.

Typical rust spots develop at the tips of the rear quarter panels at the transition to the door and sill. Moisture and dirt collect there. Rust can grow from the inside out and is often only visible at a late stage.

The Vario roof contains 11 hydraulic cylinders. The seals become porous with age; escaping oil damages trim panels and the boot. Seal sets for all cylinders are available for around 99 EUR.

Despite the hardtop, water enters the boot. Porous seals at the interlocking points of the Vario roof as well as blocked drainage channels at the rear screen.