Lot 126013: 1999 Mercedes-Benz SLK230 Kompressor Sport

The 1999 Mercedes-Benz SLK230 Kompressor (R170) is generally a solid modern classic, but like any 25+ year-old German car, it has a few well-documented trouble spots. Here are the most common issues owners report:

🔌 Electrical Issues

K40 Relay Module – Perhaps the most notorious R170 problem. This relay box (located in the fuse box near the battery) controls power to the ECU, fuel pump, and cooling fan. The solder joints crack over time, causing stalling, hard starting, cooling fans stuck on high, or the car going into limp mode. It’s fixable with a soldering iron or replacement.

MAF (Mass Airflow) Sensor – Failures are common and cause rough running, limp mode, or the engine not revving past ~3,000 RPM. A relatively inexpensive part that’s easy to replace.

🌪️ Supercharger (Kompressor)

Clutch Pulley Issues – Early R170 models (like your ‘99) use a magnetic clutch on the Eaton M45 supercharger rather than a fixed pulley. These clutches can fail, meaning the supercharger doesn’t engage when it should—sapping power. You may hear a distinct “click” when the clutch engages; silence under acceleration often indicates a problem.

Intercooler/Boost Leaks – Check hoses and connections around the intercooler for leaks that reduce boost pressure.

🏠 Vario Roof (Power Hardtop)

The SLK’s signature retractable hardtop is a complex hydraulic system. Age, not mileage, is the enemy here:

• Hydraulic Pump Failure – The pump (located in the trunk) can leak or fail; replacement is pricey.
• Cylinder Leaks – The roof’s hydraulic cylinders can seep fluid over time.
• Microswitch Problems – Faulty switches prevent the roof from completing its cycle.
• Seal Degradation – Rubber seals harden and can cause leaks even with a hardtop.

🔒 PSE Pump (Central Locking)

The Pneumatic System Equipment (PSE) pump in the trunk operates the central locking, fuel filler release, and trunk release via vacuum lines. The pump itself can fail, or—more commonly—the rubber air lines crack and leak. Symptoms include non-working door locks or a constantly running pump.

🛠️ Suspension & Chassis

Control Arm Bushings – The front multi-link suspension uses rubber bushings that dry out and crack with age. You’ll feel clunking over bumps or wandering steering.

Ball Joints – Upper control arms and lower ball joints wear and are common replacement items.

🦀 Rust

Despite galvanizing, R170s can rust in predictable spots:

• Wheel arches (especially rear)
• Door sills and rocker panels
• Trunk/boot edges and seal areas
• Undercarriage near jack points

🎯 Context for This Specific Car

Given this example has only 2,881 original miles, several “wear” items (bushings, ball joints, brakes) are likely in excellent shape. However, age-related issues still apply:

• Rubber seals on the Vario Roof need inspection
• Hydraulic fluid in the roof system may need service
• K40 relay could still act up—it’s age, not mileage dependent
• Tires likely need replacement due to age, not wear

The M111 engine is robust—change the oil regularly and the supercharger will likely outlast the car!

Want me to find similar low-mileage SLK230s or help you dig deeper into any of these issues?