2018 Mercedes-Benz S400L

The 2018 Mercedes-Benz S400L is a luxury sedan known for its opulent interior, smooth ride, and advanced technology features. In the US market, the S400L was specifically offered with a 3.0L Turbocharged V6 engine. This engine produces 362 horsepower and 369 lb-ft of torque. A common praise for this vehicle is the luxurious interior, comfortable ride, and available technology. Complaints often revolve around the cost of maintenance, complex electronics, and occasional issues with the air suspension. Other engine options available in the S-Class lineup included V8 and V12 engines, but these were not specifically available for the S400L model. The S400L is equipped with a 9G-TRONIC 9-speed automatic transmission.

Engine

3.0L Turbocharged V6

• Oil Leaks from Turbocharger Oil Lines
  • Description/Symptoms: Oil leaks are observed near the turbocharger area. Burning oil smell may also be present.
  • Solution: Replace the turbocharger oil supply and return lines, including sealing washers.
  • Estimated Cost to Fix: $500 - $800+
  • Recalls: None Found
• High-Pressure Fuel Pump Failure
  • Description/Symptoms: Engine misfires, rough idling, difficulty starting, or complete failure to start. Diagnostic trouble codes (DTCs) related to fuel pressure may be present.
  • Solution: Replacement of the high-pressure fuel pump. May also require replacement of fuel lines if contaminated.
  • Estimated Cost to Fix: $1200 - $2000+
  • Recalls: None Found

Transmission

9G-TRONIC 9-Speed Automatic Transmission

• Harsh Shifting/Slipping
  • Description/Symptoms: Noticeable harsh or jerky shifts between gears. Transmission may slip or hesitate during acceleration.
  • Solution: In some cases, a software update/reprogramming of the transmission control module (TCM) can resolve the issue. More severe cases may require valve body replacement or complete transmission overhaul.
  • Estimated Cost to Fix: $300 (software update) to $4000+ (transmission overhaul)
  • Recalls: None Found

Suspension

• Airmatic Suspension Leaks/Failure
  • Description/Symptoms: Vehicle sits lower than normal, especially on one side. “Vehicle Level Too Low” warning message displayed. Hissing sound may be heard from the air struts.
  • Solution: Replacement of leaking air struts or air compressor. Diagnostic testing to identify the source of the leak is crucial.
  • Estimated Cost to Fix: $1500 - $3000+ per strut, $800 - $1500+ for compressor.
  • Recalls: None Found

Electrical

• COMAND System Issues
  • Description/Symptoms: Freezing, lagging, or complete failure of the COMAND infotainment system. Navigation malfunctions, Bluetooth connectivity problems, and screen flickering may occur.
  • Solution: Software update, replacement of the COMAND head unit, or repair of wiring harness issues.
  • Estimated Cost to Fix: $300 (software update) to $2000+ (head unit replacement).
  • Recalls: None Found
• Battery Drain
  • Description/Symptoms: The vehicle will not start after being parked for a short period of time
  • Solution: Technicians will need to do a parasitic draw test to determine which module is failing to go to sleep after the vehicle has been turned off.
  • Estimated Cost to Fix: $100-$200 for diagnostic, $100-$2000+ for faulty module replacement
  • Recalls: None Found

Exterior

• Sensor Malfunctions (Parking Sensors, Blind Spot Monitoring)
  • Description/Symptoms: False alarms or complete failure of parking sensors. Blind spot monitoring system may not function correctly.
  • Solution: Replacement of faulty sensors, checking wiring connections, or recalibration of the system.
  • Estimated Cost to Fix: $300 - $800+ per sensor.
  • Recalls: None Found

Interior

• Sunroof Issues
  • Description/Symptoms: Sunroof may not open or close properly. Excessive noise during operation.
  • Solution: Lubrication of tracks, replacement of sunroof motor, or repair of linkage components.
  • Estimated Cost to Fix: $200 - $1000+
  • Recalls: None Found

Summary:

The 2018 Mercedes-Benz S400L offers a luxurious driving experience, but it is not without its potential issues. Common problems revolve around the air suspension, electrical components (especially the COMAND system), and potential engine issues like oil leaks. Transmission issues are also a concern. Repairs can be costly, particularly those involving the air suspension and complex electronics. Owners should be prepared for higher than average maintenance costs associated with this luxury vehicle.