According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 1999 Mercedes-Benz SLK/SLC has 3 documented known issues, with 1 rated critical. The most serious is R170 Tail Lamp Socket Thermal Deformation (NHTSA Recall 05V505) ($0-$450 repair). Across all issues with published estimates, repair costs range from $80 to $450. DIY maintenance guides at au7o.io.
On the 1998-2004 Mercedes-Benz SLK/SLC, on first-generation R170 SLKs, heat generated by the brake bulbs causes the base of the tail-lamp bulb sockets to deform over time, loosening the socket-to-bulb electrical contact and potentially causing the brake and tail bulbs to stop illuminating - a rear-end collision risk. Mercedes-Benz USA issued NHTSA safety recall 05V505 covering approximately 32,618 model-year 1998-2004 SLK-Class vehicles.
Common Symptoms
Brake or tail lamp bulb fails to illuminate
Melted or deformed bulb socket / housing
Bulb difficult to seat in socket
Bulb-out warning on dash
Intermittent flicker of rear lamps
How to Fix
Under recall 05V505 the dealer installs redesigned tail-lamp assemblies made from more heat-resistant material with enhanced lamp-holder mountings at no cost (about 1 hour labor). Vehicles outside the recall need the tail-lamp housing/assembly replaced, since the melted socket cannot be reliably repaired. Verify the recall was performed via VIN before purchase.
On the 1998-2004 Mercedes-Benz SLK/SLC, the pneumatic system equipment (PSE) vacuum pump that operates the central locking is repeatedly described by R170 owners as the single most failure-prone part on the car. It is mounted in the trunk and also controls the alarm, rear demister and interior light. Water ingress into the boot corrodes the pump's internal circuit board, and a torn vacuum diaphragm in a door-lock or fuel-flap actuator creates a leak that makes the pump run continuously and burn out. The result is doors that won't lock/unlock from the fob or interior switches, and sometimes a randomly triggering alarm.
Common Symptoms
Key fob won't lock/unlock any door
Interior lock switch does nothing
Vacuum pump clicks or runs continuously
Alarm triggering randomly
Corroded PSE circuit board from water ingress
How to Fix
Repair or replace the PSE pump: clean the corroded circuit board and connectors, dry out any water in the casing, replace the failed diaphragm/actuator that is leaking vacuum, and confirm the three vacuum lines are reconnected in the correct order. A full replacement PSE unit is the durable fix if the board is too far gone. Fixing the underlying boot water leak prevents recurrence.
On the 1998-2011 Mercedes-Benz SLK/SLC, sLKs (R170 and R171) frequently suffer water intrusion into the trunk and spare-wheel well. The usual culprits are clogged roof/rear-window drain tubes (which fill with leaf mulch and moss), a blocked drain under the spare well, and perished or misaligned boot seals - especially where the seal turns the rear corners. Water collects in the spare well and soaks the boot carpet, producing damp, mildew smells and, if it reaches control modules (notably the trunk-mounted PSE pump on R170), electrical faults.
Clear the boot/roof drain tubes and the spare-well drain, and re-seat or replace the boot seal. Owners diagnose the entry point by drying the boot and pouring water over the rear of the car to find the ingress point. Catching it early keeps repairs cheap; ignoring it risks a corroded PSE pump and a rusted spare well.
What are the most common Mercedes-Benz SLK/SLC problems?
According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 1999 Mercedes-Benz SLK/SLC has 3 documented issues. The most frequently reported are: R170 Tail Lamp Socket Thermal Deformation (NHTSA Recall 05V505), Central Locking PSE Vacuum Pump Failure (R170), Water Leaks into Trunk and Spare-Wheel Well from Blocked Drains / Boot Seals. Of these, 1 is rated critical and should be addressed promptly.
Is the Mercedes-Benz SLK/SLC reliable?
The 1999 Mercedes-Benz SLK/SLC has 3 known issues compiled from NHTSA recalls, manufacturer TSBs, and owner forum reports. 1 issue is rated critical: R170 Tail Lamp Socket Thermal Deformation (NHTSA Recall 05V505). Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
How much does it cost to fix common Mercedes-Benz SLK/SLC problems?
Repair costs for known Mercedes-Benz SLK/SLC issues range from $0 to $450, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, R170 Tail Lamp Socket Thermal Deformation (NHTSA Recall 05V505), typically costs $0-$450 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
What is the 1998-2004 Mercedes-Benz SLK/SLC R170 Tail Lamp Socket Thermal Deformation (NHTSA Recall 05V505)?
On first-generation R170 SLKs, heat generated by the brake bulbs causes the base of the tail-lamp bulb sockets to deform over time, loosening the socket-to-bulb electrical contact and potentially causing the brake and tail bulbs to stop illuminating - a rear-end collision risk. M… Repairs typically run $0-$450. Severity: high.
What is the 1998-2004 Mercedes-Benz SLK/SLC Central Locking PSE Vacuum Pump Failure (R170)?
The pneumatic system equipment (PSE) vacuum pump that operates the central locking is repeatedly described by R170 owners as the single most failure-prone part on the car. It is mounted in the trunk and also controls the alarm, rear demister and interior light. Water ingress into… Repairs typically run $80-$400. Severity: medium.
What is the 1998-2011 Mercedes-Benz SLK/SLC Water Leaks into Trunk and Spare-Wheel Well from Blocked Drains / Boot Seals?
SLKs (R170 and R171) frequently suffer water intrusion into the trunk and spare-wheel well. The usual culprits are clogged roof/rear-window drain tubes (which fill with leaf mulch and moss), a blocked drain under the spare well, and perished or misaligned boot seals - especially… Repairs typically run $0-$350. Severity: medium.
Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.
