2002 MERCEDES-BENZ SLK32 AMG R170

Typical onset: 60,000-100,000 mi

Symptoms: Rod knock or main bearing rumble, especially cold start, Metal shavings in oil or filter during changes, Low oil pressure warnings at idle after warm-up, Catastrophic failure: loss of power, violent knocking, seized engine

Fix: The M112K suffers from inadequate oiling to rod and main bearings under high load and heat from the supercharger. Sludge buildup accelerates wear. Once bearings go, it's a full short block replacement or engine rebuild with crank polishing, new bearings, pistons, rings. Expect 30-40 labor hours for full rebuild or 20-25 for short block swap.

Estimated cost: $8,000-15,000

Typical onset: 70,000-110,000 mi

Symptoms: Transmission slipping between gears, especially 2-3 or 3-4 shift, Harsh or delayed engagement when cold or hot, Burnt ATF smell or dark, gritty fluid on dipstick, Limp mode activation under spirited driving or towing

Fix: The factory trans cooler is marginal for the supercharged AMG power. Overheating cooks clutch packs and valve body seals. Cooler replacement is 2-3 hours; if internal damage has occurred, expect transmission rebuild (15-20 hours) or reman swap (8-10 hours install). Always upgrade cooler and do full flush after any repair.

Estimated cost: $500-900 for cooler alone, $3,500-5,500 for rebuild with upgraded cooler

Typical onset: 80,000-130,000 mi

Symptoms: Audible whining or grinding from front of engine bay, Reduced power under boost, heat-soak feeling on consecutive pulls, Coolant weeping from pump or reservoir area, Check engine light with intake air temp codes

Fix: The intercooler circuit has its own electric coolant pump that circulates through the liquid-to-air heat exchanger. Bearings fail, impellers crack. Replacement is straightforward: 2-3 hours, drain intercooler coolant, swap pump, refill and bleed. OEM or quality aftermarket pumps required.

Estimated cost: $600-1,000

Typical onset: 60,000-100,000 mi

Symptoms: Clunk or thud when shifting from park to drive or reverse, Vibration through floor and shifter at idle in gear, Excessive driveline movement visible during throttle blip, Steering wheel shake during hard acceleration

Fix: Hydraulic transmission mounts collapse internally, especially under the torque of the supercharged V6. Rear diff mounts also contribute. Transmission mount replacement is 1.5-2 hours; diff mount another 1-1.5 hours. Replace as a set for best results. Upgraded poly mounts available but transmit more NVH.

Estimated cost: $400-700

Typical onset: varies, often age-related (15+ years)

Symptoms: Top operates slowly or hesitates mid-cycle, Hydraulic fluid pooling in trunk or under rear tonneau, Top fails to latch or un-latch fully, requiring manual assist, Pump runs excessively or strains audibly

Fix: The hydraulic rams for the folding hardtop develop seal leaks over time. Individual cylinder rebuild or replacement: 3-5 hours depending on which cylinder. Pump replacement if motor is failing: 2-3 hours. Fluid flush and system bleed essential after any work. Aftermarket seals available but OEM cylinders more reliable long-term.

Estimated cost: $800-1,500 per cylinder, $600-900 for pump

Typical onset: 100,000+ mi or after overheating event

Symptoms: External coolant seepage between head and block, White exhaust smoke, sweet smell, coolant loss with no visible leaks, Overheating episodes, especially under boost, Combustion gases in coolant reservoir, bubbling when revved

Fix: M112 head bolts are torque-to-yield and can stretch, especially if engine has been overheated or sees high boost. Requires cylinder head removal, resurfacing if warped, new gaskets, new head bolts. Both banks: 18-22 labor hours. Single bank: 10-12 hours. Critical to diagnose root cause (cooling system, intercooler pump) to prevent repeat failure.

Estimated cost: $3,000-5,000 for both banks