The R170 SLK230 Kompressor is a stylish convertible hampered by the M111 supercharged four-cylinder's catastrophic internal wear issues and transmission cooling weaknesses. When these engines fail, they fail spectacularly—often requiring complete rebuilds.
Symptoms: Excessive oil consumption (quart per 500-1000 miles), Blue smoke on startup and acceleration, Metallic knocking or rattling from bottom end, Loss of compression and power, Metal shavings in oil/filter
Fix: The M111 supercharged variant suffers premature piston ring and bearing wear due to inadequate oil supply to cylinders under boost and poor ring design. Typical fix requires complete engine rebuild with upgraded pistons/rings or short block replacement. Budget 25-35 hours labor for in-car rebuild, 18-24 hours for short block swap.
Estimated cost: $4,500-8,500
Transmission Oil Cooler Failure and Contamination
Common · high severity
Typical onset: 70,000-110,000 mi
Symptoms: Pink milkshake appearance in coolant reservoir (trans fluid mixing with coolant), Transmission slipping or delayed engagement, Overheating transmission, Coolant loss without visible external leaks
Fix: The internal transmission cooler in the radiator fails, allowing coolant and ATF to cross-contaminate. Requires radiator replacement, complete transmission flush (sometimes multiple flushes), new fluid/filter, and coolant system flush. If caught late, transmission rebuild needed. 6-10 hours labor for cooler/flush only.
Estimated cost: $1,200-2,800
Transmission Mount Collapse
Common · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Clunking when shifting from Park to Drive/Reverse, Excessive vibration at idle, Visible sagging of transmission tail, Shifter vibration during acceleration
Fix: The rubber transmission mount deteriorates and separates, allowing excessive drivetrain movement. Common wear item on these cars. Straightforward replacement but requires trans support. 2-3 hours labor.
Estimated cost: $350-550
Supercharger Clutch Bearing Failure
Occasional · medium severity
Typical onset: 90,000-140,000 mi
Symptoms: Squealing or grinding noise from front of engine under load, Loss of boost pressure and power, Intermittent supercharger engagement, Belt dust accumulation near supercharger
Fix: The electromagnetic clutch bearing in the Eaton M45 supercharger wears out. Can sometimes replace just the clutch assembly, but often requires supercharger rebuild or replacement unit. 8-12 hours labor for removal/replacement.
Estimated cost: $1,800-3,200
Hydraulic Top Mechanism Leaks and Failure
Occasional · medium severity
Symptoms: Convertible top operates slowly or incompletely, Hydraulic fluid leaking in trunk area, Top stuck in partially open position, Pump runs but top doesn't move
Fix: Hydraulic cylinders and lines for the retractable hardtop develop leaks over time, especially if car sits unused. Pump can also fail. Cylinder replacement requires top removal and system bleeding. 6-10 hours labor depending on which components fail.
Estimated cost: $1,500-3,500
Crankshaft Position Sensor Failure
Occasional · high severity
Typical onset: 70,000-120,000 mi
Symptoms: No-start condition, cranks but won't fire, Stalling while driving with no restart, Intermittent cutting out at highway speed, No RPM reading on tachometer
Fix: The crank position sensor fails due to heat exposure and leaves you stranded. Sensor itself is cheap, but access requires removing exhaust components and working in tight space. 2-3 hours labor.
Estimated cost: $300-500
Owner tips
Change oil every 3,000-4,000 miles with quality synthetic to minimize M111 internal wear—this engine is extremely oil-sensitive
Inspect transmission cooler and coolant regularly for any signs of pink contamination; catch it early to save the transmission
Check engine oil consumption religiously; if burning more than a quart every 2,000 miles, start budgeting for major engine work
Service transmission fluid every 40,000 miles regardless of 'lifetime fill' claims
Exercise the convertible top monthly even in winter to keep hydraulic seals lubricated
Only buy if you find one with documented recent engine rebuild or verified low oil consumption—unrebuilt high-mileage examples are ticking time bombs.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Unlock any single procedure for $3 — or become the founding sponsor and we generate every common job on this SLK230 Kompressor R170, with your name on each one.
Fitment notes: Battery located in trunk on right side; requires special vent tube
As an Amazon Associate, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.
Every control module on the 1998-2000 Mercedes-Benz SLK230 Kompressor R170 — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
📍 Integrated in ignition switch assembly, steering column
🔧 Star Diagnosis DAS
⚠️ Key programming required; all keys must be present for coding
Seat Control Module (SCM)0.6 hr R&Rrelearn only +0.1 hr▸ programming details
📍 Under driver seat, front rail
🔧 None (self-adapt)
⚠️ Only on power seat equipped models; memory positions lost on replacement
Bi-Xenon Control Unit (XCU)0.5 hr R&Rno coding
📍 Behind headlight assembly (each side)
⚠️ Only on Xenon-equipped models; headlight aim required after replacement
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 1999 Mercedes-Benz SLK230 Kompressor R170 2.3L I4 Supercharged M111 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.