2004 MERCEDES-BENZ SLK230 KOMPRESSOR R170

Typical onset: 80,000-140,000 mi

Symptoms: Excessive oil consumption (1 quart per 500-1000 miles), Blue smoke on startup or acceleration, Loss of compression, Rod knock or bottom-end noise, Check engine light with misfire codes

Fix: The M111 supercharged engine suffers from piston ring land failure and piston skirt cracking, leading to oil burning and eventually bearing failure. Full engine rebuild or used engine replacement is typical. Rebuild involves removing engine, disassembly, machining block/head, new pistons, rings, bearings, gaskets, seals. Expect 25-35 labor hours for rebuild, 12-18 hours for used engine swap.

Estimated cost: $4,500-8,500

Typical onset: 70,000-120,000 mi

Symptoms: Transmission fluid leaking near radiator area, Pink fluid drips under front of car, Transmission overheating, Harsh shifts when hot

Fix: The metal transmission cooler lines corrode and crack where they connect to the radiator-mounted cooler. Lines must be replaced as an assembly. Access requires removing front undertray and sometimes bumper components. 2-3 labor hours plus fluid refill and system flush.

Estimated cost: $400-700

Typical onset: 60,000-100,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive vibration at idle, Visible engine/trans movement when revving in Park, Harsh engagement into gear

Fix: The rubber transmission mount deteriorates and allows excessive drivetrain movement. The 722.6 five-speed auto sits at an angle and stresses this mount heavily. Replacement requires supporting the transmission, removing mount bolts, and installing new mount. 1.5-2.5 labor hours.

Estimated cost: $250-450

Typical onset: 90,000-150,000 mi

Symptoms: Loss of power under acceleration, High-pitched squealing from engine bay, No boost pressure, Supercharger not engaging (stays free-spinning)

Fix: The electromagnetic clutch on the Eaton M45 supercharger wears out or the coil fails. Supercharger must be removed from engine, clutch assembly replaced or rebuilt. Some techs replace entire supercharger unit with remanufactured assembly. 6-8 labor hours for clutch repair, less if swapping entire unit.

Estimated cost: $800-1,800

Typical onset: 100,000-150,000 mi

Symptoms: Coolant loss with no external leaks, White smoke from exhaust, Overheating, Oil in coolant or coolant in oil, Rough idle or misfire

Fix: The M111 can blow head gaskets, especially if overheated or if the engine has been running with worn rings (increased combustion pressure). Requires cylinder head removal, resurfacing, new gasket set, timing chain verification. Often done alongside the internal engine work if rings are also worn. 12-16 labor hours as standalone job.

Estimated cost: $2,200-3,500

Typical onset: 80,000-120,000 mi

Symptoms: Hard starting especially when hot, Hesitation or stumble under load, Stalling at idle, Fuel pump whining noise

Fix: The in-tank fuel filter clogs over time, and the fuel pump can fail. The filter is not a routine service item per Mercedes but should be replaced if fuel delivery issues arise. Requires dropping fuel tank. Often combined with fuel pump replacement. 3-4 labor hours for filter and pump together.

Estimated cost: $600-1,000

Typical onset: 70,000-130,000 mi

Symptoms: Top operates slowly or stops mid-cycle, Hydraulic fluid leaking in trunk area, Top will not latch or unlatch, Pump runs continuously or makes labored noise

Fix: The hydraulic cylinders, lines, and pump seals age and leak. Fluid leaks into the trunk. Diagnosis requires pressure testing the system. Common culprits are cylinders (replace as pair) or pump seal kit. Labor varies widely: 4-8 hours depending on component and access.

Estimated cost: $800-2,000