2016 — 2019
3.0L V6 Turbo Diesel (OM642) - 190kW GLS350d 4MATIC
Diesel
Cycle through the Airmatic suspension settings while parked and during driving; listen for any persistent hissing sounds or significant delays in ride height adjustment that might suggest a worn compressor or leaky struts.
Request a cold start and observe the engine idle; note any uneven vibrations or excessive smoke, as the OM642 engine can sometimes show its age through injector seals or glow plug module issues.
Perform a transmission check by accelerating gently through the gears; ensure there is no hesitation or 'shuddering' when shifting between lower gears, as the 9G-TRONIC transmission requires clean fluid to perform at its best.
Test the infotainment and electronic systems thoroughly; interact with the COMAND interface and seat adjustments to ensure all motorized components are responding promptly, as electrical glitches can be complex to diagnose.
Usually marks a time to ensure the transmission fluid and filter have been changed, as this is vital for the 9G-TRONIC longevity.
Consider having a professional inspect the timing chain tensioners and the intake manifold 'swirl flap' actuators for signs of wear.
Often the stage where suspension air bags or supporting control arm bushings may start to show their age and require a refresh for that premium ride quality.
Prioritize a pre-purchase inspection from an independent specialist familiar with modern Mercedes-Benz diesel engines.
Confirm the service history shows regular oil changes using the specific low-ash synthetic oil required for the DPF-equipped OM642 engine.
Check the condition of the brake rotors and pads, as the heavy weight of the GLS can lead to accelerated wear on consumables.
Verify the coolant has been replaced according to the manufacturer's schedule to prevent internal corrosion.
Ensure the DPF (Diesel Particulate Filter) is in good health by asking if the car has been used for a mix of motorway and city driving.
Estimated repair costs if issues arise
In cars of this age, it's common to consider that air springs and compressors have a finite lifespan. You might eventually need to budget for a repair if the vehicle starts sagging after sitting for a day.
The OM642 engine is well-regarded, but the seals on the oil cooler can occasionally weep over time. If this happens, it is a labor-intensive job that is worth addressing to keep the engine bay clean.
Maintaining your transmission with a scheduled flush and filter change is a great way to protect your investment. If this hasn't been done recently, it’s a proactive step to plan for.
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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