Why does my GL450 need the compressor and the springs at the same time?

Because the springs usually leaked for months before the warning, and the compressor ran itself to death covering for them. On a GL the load is high enough that a compressor past its delivery spec cannot lift the truck once new springs are fitted. We measure its output before quoting; if it still meets spec, you only pay for the springs.

Is the GL350 BlueTEC cheaper to maintain than the GL450?

Fuel economy is better and the OM642 avoids the gasoline V8 timing problems, but the diesel has its own expensive list: oil cooler seals buried under the intake, swirl flap motors and the AdBlue heater and pump. Over a long ownership the costs land close together. Airmatic and the 722.9 are the same on both and are the larger recurring items.

My 2015 GL550 leaks oil onto the exhaust. Where does it come from?

On the M278 the usual sources are the valve cover gaskets and the turbocharger oil feed and return seals, both of which drip onto the manifolds and burn off, which is why you smell it before you see a puddle. We dye the oil and pressure test the crankcase to pin the source, since a rear main seal looks identical from below once the oil has run back.

My GLS with E-Active shows a suspension warning and a battery warning together. Which is the real fault?

Usually the battery. E-Active Body Control runs on the 48-volt network, so a weak 48-volt battery or a starter-generator fault disables the suspension as a protective measure and the suspension warning follows. We read both fault memories and the 48-volt state of health before touching a strut; fixing the supply often clears the suspension message.

Can you do a Service B on a GLS with the third row and the rear climate unit?

Yes. Service B on the GL and GLS includes the cabin combination filter, brake fluid exchange, engine air filter check and the inspection, and we allow extra time for the rear HVAC and the three-row interior. It runs $349–$649 here, with the service counter reset in XENTRY so the display shows the correct next interval.

X164 GL · X166 GL / GLS · X167 GLS

Mercedes-Benz GLS and GL Repair in Dallas

The full-size GL and GLS carry three rows, nearly three tons and air suspension on every example, which is why the repair conversation for an X164, X166 or X167 almost always starts at the Airmatic system and moves to the engine second.

Get an estimate All models

Repairs covered by a 2-year/24,000-mile warranty, independent shop

Generations

Which GLS and GL generations are these?

X164 GL
2007–2012
Airmatic standard, M273 5.5 V8 in the GL450 and GL550, OM642 diesel in the GL320/GL350 BlueTEC, 722.9 throughout.
X166 GL / GLS
2013–2019
M276 biturbo V6 in the GL450/GLS450, M278 V8 in the 550, OM642 diesel; 9G-Tronic from the 2017 GLS; renamed GLS in 2017.
X167 GLS
2020–
M256 inline-six with 48 volts in the GLS450, M176 V8 in the GLS580 and Maybach; Airmatic or E-Active Body Control; 9G-Tronic.

Known failures

What goes wrong on the GLS and GL, by generation?

Problem
X164, 2007–2012: Compressor runs every time the truck is unlocked, rear sags on a full load, "Airmatic Malfunction" on long drives
Likely cause
Rear air springs and the front strut bellows leak; the compressor wears out trying to keep three tons level and the relay fails with it
The fix
Leak-down test by corner, replace failed springs or struts, replace the compressor and relay when delivery is below spec, calibrate ride height in XENTRY
Airmatic Air Suspension Repair
Problem
X164 GL450 and GL550 with M273, 2007–2008: P0016 and P0018 correlation codes on both banks, rough idle after warm-up
Likely cause
Early M273 idler gear teeth wear and let both camshafts drift, the V8 version of the M272 balance shaft issue
The fix
Serial-number check and cam deviation reading, then replace the idler gear with the chains, guides and tensioners
M272/M273 Balance Shaft and Timing Chain Repair
Problem
X164 and X166, 2007–2016: Delayed engagement from park, harsh downshifts, limp mode on the highway after a long hot run
Likely cause
The 722.9 conductor plate speed sensors fail with heat cycling; a heavy GL working its transmission in July accelerates it
The fix
Conductor plate with coding, or the complete valve body where the solenoids have also drifted, with fresh fluid and filter and adaptation
722.9 7G-Tronic Transmission Service and Repair
Problem
X166, 2013–2019: Burning oil smell at stop lights, oil film on the lower engine, low oil warning between services
Likely cause
M276 and M278 oil cooler seals, valve cover gaskets and the turbo oil feed and return seals on the M278 leak under heat
The fix
Dye and pressure trace, reseal the confirmed source, replace the cooler seals with the intake off when they are weeping
M272/M273 Oil Leak Repair
Problem
X166, 2013–2019: Ride goes harsh or floaty, "ADS Malfunction" alongside an Airmatic warning
Likely cause
The adaptive damping valves on the struts fail or their connectors corrode, and the front struts leak at the top seal
The fix
Guided ADS test to isolate the valve from the wiring, replace the strut as an assembly, calibrate
Airmatic Air Suspension Repair
Problem
X167, 2020–: Suspension warning plus a battery warning, truck drops to its bump stops at one corner after parking
Likely cause
E-Active Body Control depends on the 48-volt supply; a weak 48-volt battery or starter-generator fault disables it, and the strut air lines leak at the fittings
The fix
Read the 48-volt state of health and the E-Active fault memory together, repair the leak, restore the supply, then run the level and camera calibration
Airmatic Air Suspension Repair
Problem
X167 GLS450 with M256, 2020–: Engine stalls while coasting to a stop, battery warning, slow restart
Likely cause
Integrated starter-generator or the 48-volt coolant pump, with software states that need the latest release
The fix
XENTRY quick test, replace the failed 48-volt component with VIN coding, apply the open software measures
XENTRY Diagnostics

What are the service intervals for the GLS and GL?

Service A: 10,000 miles or 1 year; MB 229.5 on the gasoline engines, MB 229.51 or 229.52 low-ash oil on the BlueTEC diesel
Service B: 20,000 miles or 2 years with brake fluid exchange and cabin filter; the three-row filter housing takes longer than on a GLE
Transmission fluid: 722.9 fluid and filter at the booklet mileage, pulled earlier on trucks that tow; 9G-Tronic checked for level and color at every B
Airmatic and ADS: Corner leak-down and compressor run time at every service; ADS damper response checked with the guided test when the ride complaint exists
Brakes: Pad and rotor thickness measured every A service; a GL at full weight wears front pads faster than its mileage suggests
Diesel exhaust fluid: BlueTEC GL320 and GL350: AdBlue level and heater function verified every service to avoid the countdown no-start

Why does Airmatic matter more on a GL than on any other Mercedes SUV?

Every GL and GLS left the factory on air suspension, and the truck weighs close to 5,500 pounds before passengers and luggage. The air springs on an X164 or X166 cycle under far more load than the same design does on a GLE, and the compressor works harder for longer. That is why the GL is the model where a compressor and two rear springs arrive together, rather than one component at a time.

The X164 shows it first. By the time a 2008 or 2010 GL450 reaches us the rear springs have usually been replaced once, and the question is whether the compressor was replaced with them. If it was not, it is near the end of its life and the relay is often already stuck. We measure the pump-up time and the pressure the compressor reaches before we quote anything.

On the X166 the struts carry adaptive damping valves, so an Airmatic warning can be a damper fault rather than a leak. The guided test in XENTRY separates the two. Replacing a damper means the whole strut, and the ride-height calibration afterwards is not optional; a GL calibrated by eye wears its tires and loads its steering geometry wrong.

Which X164 GL engines have the idler gear and conductor plate problems?

The GL450 and GL550 from 2007 and 2008 use early M273 V8s, and a subset of those have the soft idler gear that is the V8 counterpart of the M272 balance shaft issue. The symptom is a correlation code on both banks at once, because the single idler drives the chains for both sides. We verify the engine serial number before anyone talks about opening the timing cover; many 2009-on GLs show a single-bank code from an adjuster solenoid instead.

The GL320 and GL350 BlueTEC use the OM642 diesel, which escapes the timing problem but has its own list: oil cooler seals deep in the valley, swirl flap motor faults and the AdBlue system. The oil cooler job on an X164 is a long one because the intake and turbo plumbing come off to reach the cooler.

All X164s use the 722.9, and the conductor plate failure hits the GL hard because the transmission runs hot under its weight. A GL that goes to limp mode after a long run on I-635 and drives normally after cooling is the typical presentation. The repair is the conductor plate with coding and fresh fluid; where solenoid values have also drifted we quote the complete valve body instead.

What should an X166 GL or GLS owner expect after 80,000 miles?

Oil leaks come first. The M276 and M278 both run hot and the seals that fail are predictable: valve cover gaskets, the oil cooler seals under the intake, and on the M278 the oil feed and return lines to the turbochargers. We trace with dye and a pressure test, because the oil runs down the back of the engine and pools where it did not start.

The transmission depends on the year. Through 2016 the X166 uses the 722.9 with the same conductor plate and valve body wear the X164 had. The 2017-on GLS has the 9G-Tronic, which is reliable but needs correct fluid level and an adaptation reset after a battery or module change, and a GLS that tows has fluid that ages well ahead of the booklet mileage.

Airmatic and ADS faults, cooling fan and thermostat failures, and front brake wear round out the list. A 5,500-pound truck with a tall center of gravity chews through front pads and rotors, so we measure them at every A service rather than waiting for the sensor.

How is the X167 GLS different to diagnose?

The 2020-on X167 added a 48-volt network on the GLS450 and E-Active Body Control as an option on every engine. E-Active uses the 48-volt supply to drive hydraulic pumps at each strut, which means a tired 48-volt battery or a starter-generator fault can disable the suspension and put two warnings on the cluster at the same time. Diagnosis has to start with the electrical side; replacing a strut for a supply problem fixes nothing.

The GLS580 and the Maybach GLS use the M176 or M177 V8 with the same 48-volt starter-generator, and the GLS450 uses the M256 inline-six. The coolant pump for the 48-volt components and the DC/DC converter are the two parts that fail most often beyond the generator itself. All three carry VIN coding and a software release check after replacement.

Calibration on the X167 includes the forward camera that scans the road for the suspension, so a windshield replacement or a front-end repair also means a suspension recalibration. We perform it with XENTRY as part of the job.

What does a GL or GLS cost to keep on the road in Dallas?

Plan on the Airmatic system as a recurring line item: a compressor every six to eight years, air springs or struts by the corner as they age. Transmission service, oil leaks and brakes are the other recurring costs, and all of them are listed as ranges below so there is no surprise when the written estimate arrives.

Owners who tow a boat trailer to Lake Ray Hubbard or run the family out I-30 every weekend should expect the shorter end of every interval. Heat and load are the two things that age a GL, and Dallas supplies both. Repairs are covered for 2 years parts and 2 years labor, up to 24,000 miles, nationwide; email service@mercedesbenzrepair.net with the year and trim to get a written range.

Costs

What do GLS and GL repairs cost in Dallas?

What do GLS and GL repairs cost in Dallas?
Service	Price range	Typical time
Airmatic compressor with relay	$700–$1,300	2–3 hours
Airmatic strut or air spring (per corner)	$1,100–$2,200	2–3 hours
Airmatic valve block	$450–$850	2–3 hours
M273 idler gear (2007–2008 GL450/GL550)	$3,200–$5,000	2–4 days
722.9 valve body with conductor plate	$1,900–$3,200	4–8 hours
Oil cooler seals	$650–$1,100	4–8 hours
XENTRY diagnostics	$149–$229	1–1.5 hours

Typical independent-shop ranges in Dallas for the X164, X166 and X167. Diesel versus gasoline, ADS or E-Active fitment and how many corners of the suspension have failed set the final figure, which the written estimate states before any part is ordered.

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