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2009 Mercedes-Benz ML320

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By Research the Car 5 min read

The 2009 Mercedes-Benz ML320 is a mid-size luxury SUV that offers a blend of comfort, capability, and style. The ML320 designation in 2009 specifically refers to the diesel engine option. Other engine options for this model year included a 3.5L V6 gasoline engine (ML350) and a 5.5L V8 gasoline engine (ML550). The ML320 features a 3.0L turbodiesel V6 engine producing 215 horsepower and 398 lb-ft of torque. Owners generally praise the ML320 for its fuel economy compared to the gasoline options, its smooth ride, and its luxurious interior. Common complaints revolve around higher maintenance costs compared to non-luxury SUVs, and potential reliability issues with certain components, particularly related to the diesel emissions systems and electrical systems. All engines are paired with a 7-speed automatic transmission.

Engine

3.0L Turbodiesel V6 (ML320 CDI)

  • Oil Cooler Seal Leaks
    • Description/Symptoms: Oil leaks are common around the oil cooler seals. The leak can be slow initially but can worsen over time, leading to oil loss and potential engine damage if not addressed. Oil spots may be visible under the vehicle.
    • Solution: Replace the oil cooler seals.
    • Estimated Cost to Fix: $300 - $600
    • Recalls: None Found
  • Glow Plug Failure
    • Description/Symptoms: Diesel engines use glow plugs to preheat the cylinders for easier starting, especially in cold weather. If one or more glow plugs fail, the engine may be difficult to start, particularly in cold conditions. A check engine light may illuminate.
    • Solution: Replace the faulty glow plug(s) and control module if necessary.
    • Estimated Cost to Fix: $150 - $400+ (depending on how many plugs and if the module is needed)
    • Recalls: None Found
  • Diesel Particulate Filter (DPF) Issues
    • Description/Symptoms: The DPF can become clogged, leading to reduced engine performance, increased fuel consumption, and a check engine light. This is often caused by short trips where the DPF doesn’t get hot enough to regenerate.
    • Solution: Attempt a forced regeneration of the DPF (performed by a mechanic with the appropriate diagnostic tool). If regeneration is not successful, the DPF may need to be cleaned or replaced.
    • Estimated Cost to Fix: $200 (forced regeneration) to $1500+ (DPF replacement)
    • Recalls: None Found
  • EGR Valve Failure
    • Description/Symptoms: The EGR valve can become clogged with carbon deposits, causing rough idling, poor acceleration, and a check engine light.
    • Solution: Clean or replace the EGR valve.
    • Estimated Cost to Fix: $200 - $500
    • Recalls: None Found

3.5L Gasoline V6 (ML350)

  • No Issues Found

5.5L Gasoline V8 (ML550)

  • No Issues Found

Transmission

7-Speed Automatic (7G-Tronic) - All Engine Options

  • Valve Body Issues
    • Description/Symptoms: The 7G-Tronic transmission can experience issues with the valve body, leading to harsh or erratic shifting, slipping between gears, or a complete loss of gear engagement.
    • Solution: Replace or rebuild the valve body. In some cases, flushing the transmission fluid and replacing the filter can temporarily alleviate the issue, but it is not a permanent fix.
    • Estimated Cost to Fix: $800 - $2000+ (depending on whether it is rebuilt or replaced)
    • Recalls: None Found
  • Torque Converter Failure
    • Description/Symptoms: The torque converter can fail, leading to shuddering, vibration, or a complete loss of power transfer.
    • Solution: Replace the torque converter.
    • Estimated Cost to Fix: $1000 - $2500+
    • Recalls: None Found

Suspension

  • Airmatic Air Suspension Problems (If Equipped)
    • Description/Symptoms: The Airmatic air suspension (optional) is prone to leaks in the air springs, leading to the vehicle sagging or leaning to one side. The air compressor can also fail, preventing the system from maintaining the correct ride height. Warning lights will typically illuminate on the dashboard.
    • Solution: Replace the leaking air spring(s) and/or the air compressor. It is generally recommended to replace air springs in pairs.
    • Estimated Cost to Fix: $500 - $1500+ per air spring; $600 - $1200+ for the compressor
    • Recalls: None Found
  • Suspension Bushing Wear
    • Description/Symptoms: Worn control arm bushings and sway bar bushings can cause clunking noises, especially when going over bumps. The vehicle may also feel loose or unstable in corners.
    • Solution: Replace the worn bushings. In some cases, it may be necessary to replace the entire control arm.
    • Estimated Cost to Fix: $200 - $800+ (depending on the bushing and whether the control arm needs to be replaced)
    • Recalls: None Found

Electrical

  • EIS (Electronic Ignition Switch) Failure
    • Description/Symptoms: The EIS can fail, preventing the vehicle from starting or unlocking the steering wheel.
    • Solution: Replace the EIS module. This often requires programming by a qualified technician.
    • Estimated Cost to Fix: $800 - $1500+
    • Recalls: None Found
  • SAM (Signal Acquisition Module) Issues
    • Description/Symptoms: The SAM controls various electrical functions, and failures can cause a wide range of problems, including lighting issues, windshield wiper malfunction, and problems with the door locks.
    • Solution: Diagnose the specific SAM module that is failing (front, rear, etc.) and replace it. Programming may be required.
    • Estimated Cost to Fix: $500 - $1200+
    • Recalls: None Found
  • Battery Drain
    • Description/Symptoms: Excessive battery drain can cause the vehicle to not start after sitting for a short period. This can be due to a faulty module or a parasitic draw.
    • Solution: Diagnose and repair the source of the battery drain.
    • Estimated Cost to Fix: $100 - $500+ (depending on the cause)
    • Recalls: None Found

Exterior

  • Tail Light Bulb Failure
    • Description/Symptoms: Rear tail light bulbs frequently burn out, often triggering a warning message on the dashboard.
    • Solution: Replace the burnt-out bulb.
    • Estimated Cost to Fix: $10 - $50+ (depending on the bulb and labor)
    • Recalls: None Found

Interior

  • Sunroof Issues
    • Description/Symptoms: The sunroof mechanism can fail, causing the sunroof to get stuck, leak, or make excessive noise.
    • Solution: Repair or replace the sunroof mechanism.
    • Estimated Cost to Fix: $300 - $1000+
    • Recalls: None Found

Summary

The 2009 Mercedes-Benz ML320, while offering luxury and capability, can be prone to certain issues. The most significant potential problems relate to the diesel engine (ML320 CDI), the Airmatic air suspension (if equipped), the 7G-Tronic transmission, and various electrical components. Repairs can be costly, especially for the air suspension, transmission, and electrical system components. The diesel-specific issues like DPF clogging and EGR valve failures also contribute to higher maintenance costs for the ML320. Although the gasoline-powered models do not have significant engine issues, they may still be subject to suspension, transmission, and electrical issues. Overall, it’s important to have a qualified mechanic inspect the vehicle before purchase, especially if it is an ML320, and to budget for potential repairs.

Mercedes-Benz, ML320
Mercedes-Benz ML320 2009
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