2012 — 2016
4.7L V8 Bi-Turbo (M278) - GL 500/GL 550
Petrol
While driving, gently coast at low speeds and listen for any rhythmic clicking or vibrations from the air suspension struts, as the Airmatic system can develop leaks or compressor fatigue in higher-mileage examples.
Check the engine bay after a warm-up; observe the valley of the engine for any signs of oil pooling, as the M278 engine's oil separator gaskets are known to occasionally weep over time.
Operate the COMAND infotainment system and verify the heated/cooled seat functions; these electronic comfort features are complex and it is common for the seat ventilation fans or control modules to require maintenance in older luxury SUVs.
Put the vehicle in reverse and drive forward in a quiet area; listen for any clunks from the transmission or differential mounts, which may show signs of wear given the significant torque the V8 Bi-Turbo produces.
Time to inspect timing chain tensioners and check the health of the auxiliary battery which supports the start-stop system.
Consider a full service of the 7G-Tronic transmission fluid and filter, and keep an eye on the air suspension compressor relay.
Monitor the condition of cooling system components like the water pump and thermostat, which are common service items for engines of this age and complexity.
Prioritize oil changes every 10,000km using high-quality synthetic oil to protect those intricate Bi-Turbo components.
Regularly inspect the drain holes under the windscreen cowl; keeping these clear prevents water ingress into the cabin electronics.
Ensure the transmission fluid and filter have been refreshed according to the recommended intervals to maintain smooth shifting.
Check the condition of the brake pads and rotors during every service, as the GL is a heavy vehicle that puts significant demand on the braking system.
Keep the sunroof tracks clean and lubricated to ensure the mechanism operates smoothly and maintains a proper seal.
Estimated repair costs if issues arise
If the vehicle begins to sag overnight or the compressor struggles to level the ride, you might eventually need to budget for strut or compressor replacement to maintain that signature smooth ride.
Depending on the car's maintenance history, it's worth keeping an eye on the cold-start timing chain rattle. It is common to consider replacing these as preventative maintenance to avoid further engine wear.
In cars of this age, small leaks can develop in the turbo cooling system. If this component needs attention in the future, the job involves addressing seals or lines to prevent minor fluid loss.
Noticed something inaccurate or missing?Suggest an edit→
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