The 2007 GL550 X164 with the M273 5.5L V8 is a capable luxury SUV plagued by catastrophic engine failure due to balance shaft wear causing scored cylinder walls, plus typical Mercedes air suspension and transmission cooler issues that make it a high-risk used purchase without comprehensive service records.
Symptoms: Cold-start engine rattle for 2-3 seconds that disappears when warm, Metal shavings in oil during changes, Gradually increasing oil consumption (1 qt per 500-1000 mi), Eventually rough idle, misfire codes, catastrophic bearing failure
Fix: Balance shaft sprockets wear and send metal through the engine, scoring cylinder walls and wiping bearings. Only real fix is full engine rebuild or replacement: block honing if caught early (rare), usually needs pistons, rings, bearings, and machine work. 40-60 labor hours for proper rebuild.
Estimated cost: $8,000-15,000
Transmission Oil Cooler Line Failure
Common · high severity
Typical onset: 60,000-120,000 mi
Symptoms: Transmission fluid leaking from front of vehicle near radiator, Transmission overheating warnings, Harsh shifting or slipping after fluid loss, Pink or red fluid pooling under engine bay
Fix: The 722.9 seven-speed transmission cooler lines corrode and fail at crimped connections. Requires cooler line replacement and often full transmission service with filter and fluid. If driven low on fluid, transmission damage adds thousands. 3-5 labor hours.
Estimated cost: $800-1,500
AIRMATIC Air Suspension Compressor & Strut Failure
Common · medium severity
Typical onset: 70,000-130,000 mi
Symptoms: Vehicle sits low on one or more corners, especially after sitting overnight, AIRMATIC warning on dash with vehicle lowered, Compressor runs constantly (can hear it cycling), Rough ride quality, bottoming out over bumps
Fix: Air struts leak at seals, overworking the compressor until it fails. Front struts leak first usually. Each strut runs 2-3 hours labor; compressor is 3-4 hours. Many owners convert to Arnott coil spring kits to eliminate future issues.
Estimated cost: $1,200-2,800 per strut; $1,500-2,200 compressor; $2,500-4,000 coil conversion
Transmission Mount Collapse
Common · medium severity
Typical onset: 60,000-100,000 mi
Symptoms: Clunk or thud when shifting from Park to Drive or Reverse, Vibration at idle in Drive that lessens in Neutral, Excessive driveline movement visible during throttle application, Transmission case contacting crossmember in extreme cases
Fix: Hydraulic transmission mount fails internally, allowing excessive powertrain movement. Easy diagnosis with visual inspection during throttle test. 2-3 labor hours with proper support equipment.
Estimated cost: $600-1,000
Radiator and Coolant Pipe Leaks
Occasional · medium severity
Typical onset: 90,000-140,000 mi
Symptoms: Coolant dripping from front of engine or under vehicle, Sweet smell from engine bay, Coolant level dropping with no visible external leaks initially, Engine overheating warning in advanced cases
Fix: Plastic radiator end tanks crack and coolant crossover pipes at rear of heads corrode. Radiator is 3-4 hours; coolant pipes require intake manifold removal and are 8-10 hours labor. Often done together during major service.
Symptoms: Gear oil seeping from front axle near CV joints, Oil spots on garage floor under front wheels, Clunking from front axle if driven severely low on fluid
Fix: Axle seals and pinion seals leak on 4MATIC front differential. Caught early, it's seal replacement and fluid service at 2-3 hours labor per side. Ignore it and you're rebuilding the differential.
Estimated cost: $600-1,200
Owner tips
Have a pre-purchase inspection specifically check for cold-start rattle and request oil analysis for metal content — the M273 balance shaft issue is a ticking time bomb
Budget $2,000-3,000 annually for suspension and drivetrain wear items beyond normal maintenance on any X164 over 80k miles
Service transmission fluid every 40,000 miles regardless of Mercedes 'lifetime fill' claim — the 722.9 needs fresh fluid
If air suspension hasn't been replaced yet and you're buying high-mileage, factor in imminent $4,000-6,000 for all four corners or coil conversion
Only buy if you find one with documented engine rebuild or verifiable balance shaft fix and can afford $3,000-5,000 in deferred maintenance — otherwise this is a $10,000 gamble on a $15,000 engine rebuild.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: AGM battery located under hood; GL550 requires high-capacity AGM for high electrical demands
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Every control module on the 2007-2012 Mercedes-Benz GL550 X164 — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Memory seat positions stored in module. Coding required for heated/ventilated seat options.
Bi-Xenon Control Unit (XCU)0.6 hr R&Rrelearn only +0.2 hr▸ programming details
📍 Each headlight assembly (2 units)
🔧 Star Diagnosis or scan tool
⚠️ Self-leveling calibration required. High voltage; wait before handling.
Fuel Pump Control Module (FPCM)0.5 hr R&Rno coding
📍 Right rear cargo area, integrated with SAM-R circuit
⚠️ Relay-based control via SAM-R; not a separate programmable module on this platform.
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2007 Mercedes-Benz GL550 X164 5.5L V8 M273 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.