1998 MERCEDES-BENZ C230 KOMPRESSOR W202

Typical onset: 80,000-150,000 mi

Symptoms: excessive blue smoke at startup or acceleration, loss of compression in one or more cylinders, sudden drop in oil level between changes, metallic rattling from engine block, misfire codes with low compression test results

Fix: The M111 Kompressor suffers from weak piston ring lands that crack under supercharger boost, leading to blow-by and cylinder wall scoring. Repair requires full engine teardown, bore inspection, oversized pistons if walls can be saved, or sleeving/shortblock replacement if scored badly. Machine work adds 2-3 weeks. Expect 25-35 labor hours total including R&R, plus machine shop time.

Estimated cost: $4,500-8,500

Typical onset: 100,000-140,000 mi

Symptoms: grinding or whining noise from front of engine under load, loss of boost pressure, wobbling supercharger pulley, shredded rubber coupler material in accessory belt area

Fix: The Eaton M45 supercharger's front snout bearing wears, and the rubber coupler deteriorates. Supercharger must come off, bearing replaced or entire snout assembly swapped, coupler renewed. 6-8 hours labor. Rebuild kits available but quality varies—OEM parts preferred.

Estimated cost: $1,200-2,000

Typical onset: 90,000-130,000 mi

Symptoms: transmission fluid leaking near radiator, pinkish fluid puddles under front of car, low transmission fluid warnings, erratic shifting when fluid level drops

Fix: Steel cooler lines running to radiator corrode at fittings and mid-span, especially in salt-belt cars. Replace both lines preventively—they're cheap and labor overlaps. Drain trans, replace lines, refill. 2-3 hours labor. Do not ignore; running low on ATF kills the 722.6 five-speed.

Estimated cost: $350-600

Typical onset: 70,000-110,000 mi

Symptoms: clunking when shifting from Park to Drive, excessive vibration at idle, engine rocks visibly under throttle, transmission tunnel vibration during acceleration

Fix: Hydraulic engine and transmission mounts degrade, especially front-right engine mount and rear transmission mount. Replace all four mounts as a set if one fails—they're aging together. 3-4 hours labor for all mounts. OEM Lemforder or Corteco recommended; cheap aftermarket lasts 18 months.

Estimated cost: $600-1,000

Typical onset: 120,000-160,000 mi

Symptoms: oil weeping at cylinder head to block mating surface, slight coolant smell from engine bay, minor coolant loss over months, no overheating or mixing of fluids

Fix: M111 head gaskets can weep externally at high mileage but rarely blow catastrophically unless overheated. If caught early and no piston damage present, head removal, resurface, new gasket, ARP studs recommended. 12-14 hours labor. Many skip this unless oil loss is significant—monitor closely.

Estimated cost: $1,800-2,800

Symptoms: random no-start conditions when hot, engine stalls at operating temperature then restarts when cool, tachometer drops to zero while driving, crank but no start until engine cools 20-30 minutes

Fix: Heat-sensitive crank sensor fails intermittently, leaving you stranded. Located at bell housing, accessible from underneath. 1 hour labor, cheap part. Keep a spare in the glovebox—common roadside fix for W202 owners.

Estimated cost: $150-250

Typical onset: 80,000-120,000 mi

Symptoms: window drops into door, slow or jerky window operation, clicking or grinding noise when operating windows, window stuck in down position

Fix: Plastic window regulator guides break; typical Mercedes tax item. Replace regulator assembly per door, not just clips. 1.5-2 hours per door. Do all four if budget allows—they fail serially. Aftermarket regulators work fine here.

Estimated cost: $300-500 per door