2019 — 2026
2.9L I6 Turbo (OM656) - GLS 400d Diesel
Diesel
Cycle through the Airmatic suspension settings while stationary and again at speed. Listen for any persistent compressor noise or delayed leveling, as air struts are a common wear item on these luxury SUVs.
Navigating the MBUX infotainment system thoroughly. Ensure the dual 12.3-inch screens are responsive and that the voice control system acknowledges commands, as software glitches can be frustrating to rectify.
Listen for any subtle creaks or rattles from the panoramic sunroof frame. On larger luxury SUVs like the GLS, the extensive glass housing can occasionally develop minor noises over time.
Look for any signs of weeping around the OM656 diesel engine’s auxiliary components. Given the complexity of this twin-turbo straight-six, it is worth checking the engine bay for any oil residue that might suggest future seal attention.
Time to inspect the transmission fluid and filter service, as Mercedes recommends proactive care for the 9G-TRONIC gearbox.
Consider a major service interval including differential oil changes and a detailed inspection of the cooling system components.
Monitor the AdBlue system and DPF (Diesel Particulate Filter) performance, as higher mileage examples often require a professional cleaning or sensor calibration.
Ensure the digital service history is complete and verify that all A and B service intervals have been met.
Confirm the air suspension compressor and airbags have been inspected for leaks, particularly if the vehicle has spent time in coastal environments.
Check the tire condition specifically for uneven inner-edge wear, which can indicate a need for a wheel alignment on a vehicle of this weight.
Test all electrical door handles and soft-close mechanisms if equipped, as these convenience features rely on consistent battery health.
Verify that the MBUX software has been updated to the latest version by a certified service agent for optimal system stability.
Estimated repair costs if issues arise
While the Airmatic system provides a peerless ride, individual struts or the compressor can eventually require replacement. As a proactive measure, it is sensible to set aside a contingency fund should a leak develop over time.
Regular fluid changes are the secret to the longevity of the 9-speed transmission. Depending on the car's current mileage, you might eventually need to budget for a comprehensive flush and filter kit to keep shifting smooth.
The GLS 400d is a substantial vehicle, and as such, it works its brakes quite hard. When the time comes for new pads and rotors, opting for high-quality replacements is recommended for safety and performance.
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Disclaimer: This report is generated with the assistance of AI analysis based on verified automotive data. While we strive for 100% accuracy, enthusiasts should always conduct physical inspections and consult service records. View Full Disclaimer