2009 Mercedes-Benz GL450

The 2009 Mercedes-Benz GL450 is a full-size luxury SUV known for its spacious interior, comfortable ride, and capable performance. In addition to the GL450, the 2009 GL-Class was available as the GL320 CDI with a 3.0L diesel engine, the GL550 with a 5.5L V8 and the AMG GL63 with a 6.2L V8. The GL450 comes equipped with a 4.7L V8 engine producing 335 horsepower and 339 lb-ft of torque and is paired with a 7G-TRONIC seven-speed automatic transmission. Owners generally appreciate the GL450’s luxurious features and smooth ride, but some common complaints include high maintenance costs and electrical issues.

Engine

4.7L V8

• Camshaft Adjuster Failure
  • Description/Symptoms: Check engine light illumination, rough idling, engine noise, and potential damage to other engine components.
  • Solution: Replacement of the camshaft adjusters (phasers).
  • Estimated Cost to Fix: $2,000 - $4,000+
• Valve Cover Gasket Leaks
  • Description/Symptoms: Oil leaks visible around the valve covers, burning oil smell, and low oil levels.
  • Solution: Replacement of the valve cover gaskets.
  • Estimated Cost to Fix: $500 - $1,000
• Coolant Leaks (Radiator and Hoses)
  • Description/Symptoms: Overheating, low coolant levels, visible coolant leaks.
  • Solution: Replacement of the leaking radiator and/or hoses.
  • Estimated Cost to Fix: $400 - $1,200+

Transmission

7G-TRONIC Seven-Speed Automatic

• Torque Converter Failure
  • Description/Symptoms: Shuddering during acceleration, erratic shifting, transmission slipping.
  • Solution: Replacement of the torque converter.
  • Estimated Cost to Fix: $1,500 - $3,000+
• Valve Body Issues
  • Description/Symptoms: Harsh or delayed shifting, transmission slipping, and difficulty engaging gears.
  • Solution: Replacement or rebuild of the valve body.
  • Estimated Cost to Fix: $800 - $2,000+

Suspension

• Airmatic Suspension Failure
  • Description/Symptoms: Vehicle sagging on one or more corners, compressor failure, “Vehicle Too Low” warning light.
  • Solution: Replacement of the air struts, compressor, or valve block.
  • Estimated Cost to Fix: $800 - $2,000+ per strut, $500 - $1,500+ for the compressor
• Air Compressor Failure
  • Description/Symptoms: Loud noise coming from the compressor, suspension not lifting properly, error messages related to the air suspension.
  • Solution: Air compressor replacement.
  • Estimated Cost to Fix: $500 - $1,500+
• Airmatic Line Leaks
  • Description/Symptoms: Hisssing sounds, vehicle sagging on one or more corners
  • Solution: Replacement of the air lines
  • Estimated Cost to Fix: $200 - $1,000+

Electrical

• Electronic Stability Program (ESP) Malfunction
  • Description/Symptoms: ESP warning light illuminated, loss of stability control, reduced engine power.
  • Solution: Diagnosis and repair of faulty wheel speed sensors, steering angle sensor, or ESP control unit.
  • Estimated Cost to Fix: $200 - $1,000+
• Battery Drain
  • Description/Symptoms: Dead battery, difficulty starting the vehicle.
  • Solution: Diagnosis and repair of parasitic drain. Culprits can include aftermarket electronics, faulty door modules, seat control module, or a malfunctioning gateway control unit.
  • Estimated Cost to Fix: $100 - $500+ (diagnosis) + cost of part replacement
• Glow Plug Module Failure (Diesel Engines)
  • Description/Symptoms: Hard starting, excessive smoke, check engine light (diesel engine only).
  • Solution: Replacement of the glow plug module and potentially the glow plugs themselves.
  • Estimated Cost to Fix: $400 - $800+
• Power Window/Door Lock Issues
  • Description/Symptoms: Intermittent or complete failure of power windows or door locks.
  • Solution: Replacement of faulty window regulators, door lock actuators, or related wiring.
  • Estimated Cost to Fix: $200 - $500 per window/door.
• COMAND System Problems
  • Description/Symptoms: Screen flickering, system freezing, navigation malfunction, Bluetooth connectivity issues.
  • Solution: Software update, replacement of the COMAND unit.
  • Estimated Cost to Fix: $100 - $1000+
• Headlight Failure (Especially HID/Xenon)
  • Description/Symptoms: One or both headlights not working.
  • Solution: Replacement of the headlight bulb or ballast.
  • Estimated Cost to Fix: $200 - $600+

Exterior

• Rust (Especially around Wheel Arches and Tailgate)
  • Description/Symptoms: Visible rust on the body panels.
  • Solution: Body repair and repainting.
  • Estimated Cost to Fix: $500 - $3,000+ depending on severity
• Tail Light/Marker Light Failure
  • Description/Symptoms: Bulb failure
  • Solution: Replacement of the bulb
  • Estimated Cost to Fix: $10-$100+

Interior

• Sunroof Issues
  • Description/Symptoms: Sunroof not opening or closing properly, or getting stuck.
  • Solution: Repair or replacement of sunroof motor, tracks, or cables.
  • Estimated Cost to Fix: $300 - $1,000+
• Third Row Seat Issues
  • Description/Symptoms: Seat not folding or unfolding, seat stuck, or making noise when moving.
  • Solution: Repair or replacement of seat motor or track system.
  • Estimated Cost to Fix: $200-$800+

Recalls:

• 2017010002 - Rear SAM Control Unit Software Update
• 2018050008 - Driver’s Side Airbag Inflator Rupture
• 2020040014 - Starter Current Limiter Overload
• 2021020004 - Rearview Camera Image Not Displayed

In summary, the 2009 Mercedes-Benz GL450, while luxurious and capable, can present owners with a range of issues, from engine and transmission problems to suspension and electrical faults. The airmatic suspension and electrical systems are particularly prone to problems and can be costly to repair. Preventative maintenance is key to mitigating these risks. The severity and cost of these repairs range from minor fixes under $500 to major overhauls exceeding $3,000, making it crucial for prospective buyers to carefully inspect the vehicle’s history and condition.