2019 — 2026
3.0L I6 Turbo Diesel (OM656) - GLS400d
Diesel
Cycle through every air suspension setting while driving at low speeds to listen for any groaning or uneven leveling, as the Airmatic system is complex.
Engage the MBUX infotainment screen and spend five minutes using the touch controls and voice commands; checking for system stutters is common practice in tech-heavy luxury SUVs.
Perform a cold start and listen carefully at the front of the engine for any timing chain rattle, which is useful to rule out potential wear in the OM656 unit.
Shift between Park, Reverse, and Drive multiple times while on a slight incline to ensure the 9G-TRONIC transmission engages smoothly without any noticeable shunting.
Usually marks the first major transmission fluid service and potential inspection of suspension bushings.
Often the time to evaluate the condition of the diesel particulate filter (DPF) and the secondary turbocharger components.
Typically the stage where preventative cooling system components, such as the water pump, are worth reviewing.
Check that the service history shows regular oil changes using Mercedes-Benz approved synthetic lubricants, as the OM656 engine is quite sensitive to oil quality.
Confirm the panoramic sunroof drain channels have been kept clear to prevent any potential moisture issues in the cabin electronics.
Verify that the AdBlue system has been maintained, as the sensor and injector can occasionally flag warnings if neglected.
Ensure the brake rotors and pads are inspected, as the heavy weight of the GLS400d means they work harder than in smaller vehicles.
Keep an eye on the software update status via the MBUX interface, as these vehicles benefit significantly from regular firmware optimizations.
Estimated repair costs if issues arise
Future Budget Planning: Over time, the rubber seals on air struts can perish. It is worth setting aside a fund for eventual replacement to maintain that signature smooth ride.
Future Budget Planning: The 9G-TRONIC transmission requires specific fluid and filter changes to keep shifting crisp. Depending on your driving style, you might eventually need to budget for a comprehensive flush.
Future Budget Planning: Modern diesel systems are intricate. If the vehicle is used primarily for short city trips, these sensors can occasionally require cleaning or replacement later in the car's life.
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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