Air Suspension That Needs Calibration, Not Just Parts

Every GLS rides on AIRMATIC air suspension, and the top trims add 48-volt active control on each wheel. A worn air strut or a faulty ride-height sensor drops a corner and lights an AIRMATIC fault on the dash. The system holds high pressure, so it has to be depressurized with a diagnostic computer before any part comes off. Fitting the new strut is only half the job, because the ride heights have to be calibrated with Mercedes Xentry afterward. Skip that calibration and the GLS sits crooked or rides wrong, even with a brand-new part installed. We depressurize the system safely, replace the failed component, and calibrate all four corners before the car leaves.

Driveshaft Flex Discs And The Center Bearing

Power reaches the GLS rear axle through a long, multi-piece driveshaft joined by rubber flex discs. Those flex discs crack around their bolt holes with age and load, and a center support bearing holds the shaft steady in the middle. A worn flex disc clunks when you shift from Park into Drive or Reverse, as the slack in the driveline takes up. Worn center bearings add a vibration that builds between 45 and 70 miles per hour. Replacing the cracked discs and the center bearing together, then setting the driveshaft, leaves no new vibration behind.

The Biturbo V8 That Runs Hot In The Middle

On the GLS V8, both turbochargers sit in the valley between the cylinder banks, where heat collects under the cover. Oil lines and seals near those turbos cook in that heat and start to weep oil onto hot metal over the years. Dirty oil or long intervals starve the turbo bearings, which spin at enormous speed on a thin film of oil. A whine or grind from the engine is a turbo bearing signaling that its oil supply fell short. We inspect the turbo oil feeds and the hot-side seals, then hold the GLS to short oil intervals on the right synthetic.

Brakes That Stop A 5,300-Pound SUV

Loaded, a GLS weighs over 5,300 pounds, and stopping that mass wears brake pads and rotors faster than on a sedan. Heavy braking on long descents heats the rotors; worn pads or thin rotors then fade when you need them most. The rear brakes use an electronic parking brake that clamps the caliper through a small motor, not a cable. That motor must be retracted with a diagnostic computer before a rear brake job, or forcing the piston damages the actuator. We retract the parking brake electronically before the rear job, then fit rotors and pads rated for the weight this SUV carries.

Front Suspension Wear Under The Weight

The same mass that wears the brakes also loads the front control arms and their bushings hard. Worn bushings and ball joints let the front end clunk over bumps and let the steering wander a little. Air suspension hides this wear for a while by holding the body level even as the joints loosen. By the time a driver feels it, the looseness shows in uneven tire wear across the front. We check every front joint and bushing by hand under load, because the air system can mask a tired one.

Schedule Your GLS Service

A GLS carries more weight and more systems than any other Mercedes SUV; waiting costs more here than on a smaller car. Take your GLS to Fremont Foreign Auto for any repair on this page, whether the trouble shows as a clunk or a warning light. Call Fremont Foreign Auto at (510) 793-6067 to get your GLS scheduled for service.