Mercedes-Benz C-Class W203 — Reliability

W203 2001–2005 1 engine

Reliability Summary

Engine M112 — 84/100 BUY
Known Issues 7

Engine in this model

BUY 84

M112

2.4-3.7L V6 NA

Three-valve V6 from the last simple Mercedes era. Nothing expensive inside; the harmonic balancer ru...

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Known Issues Across All Engines

Issue Engine Severity Onset
Harmonic balancer (crank pulley) rubber delaminates M112 high —
Oil leaks — valve-cover gaskets, front crank seal (V6), rear main seal (V8) M112 moderate —
Air suspension / Airmatic failure (S/ML models) M112 moderate 100,000 km – 180,000 km
Oil sludge from conventional oil on long FSS intervals (MY1998-2001) M112 minor —
Crankshaft position sensor fails when hot — stall or hot no-start M112 minor —
Coolant system: water pump, thermostat, expansion tank M112 minor 100,000 km – 180,000 km
Spark plugs + ignition coils (V6/V8) M112 minor 80,000 km – 150,000 km