2009 Mercedes-Benz ML350 Problems

RepairPal has identified the most common problems with the 2009 Mercedes-Benz ML350 as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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Known Problems

The 2006-2012 Mercedes Benz ML350 may have engine oil seeping or leaking from the back of the cylinder heads. This is commonly misdiagnosed as leaking valve covers.

On the back of the cylinder heads there are three, in total, plastic expansion plugs that plug access ports to the camshafts. These plugs are well known for seeping oil, and leaking if left unattended. The oil will run down the back of the engine and eventually make it to the ground. 

Replacement of these three plastic plugs is extremely simple, and should be done as regular maintenance. The recommended interval for replacement is every 60,000 miles.

The brake light warning message for a burned out bulb may be displayed. Our technicians tell us the tail lamp housing may melt and distort causing a poor connection at the bulb. The lamp housing should be replaced to correct this condition.

The engine may develop a stalling and/or no start condition due to a failed crankshaft position sensor.

Vehicles equipped with a 7-speed automatic transmission may develop a rough shifting condition, most commonly going up from first to second gear and going down from third to second or second to first gear. Our technicians tell us this is due to an internal component failure. Mercedes has released updated parts; the transmission will need to be removed and disassembled to complete the necessary repairs.

The power steering reservoir designed for the 2006-2014 Mercedes Benz ML350 commonly leaks power steering fluid causing a screeching sound when turning the steering wheel, especially when the vehicle is stopped. The power steering light may illuminate on the dash for more severe leaks.

This is caused by cracking in the plastic reservoir, or a hardened, brittle seal between the power steering reservoir and power steering pump.

Remediation involves replacing the power steering fluid reservoir, power steering fluid, bleeding the system of air, and replacement of the seal between the reservoir and power steering pump.

When starting the engine after sitting for several hours, a knocking sound may be heard for several seconds. This is a common issue with the 2006-2010 Mercedes Benz ML350. There are three common problems that can cause this sound to occur:

-Oil pressure building too slowly, allowing for movement between the crankshaft and crankshaft bearings

-Stretch or wear of timing chain and components

-Balance shaft (counter rotating shaft) gear wear

The remediation for these problems can be crankshaft bearing replacement with correct size, replacement of timing components, or balance shaft replacement.

Electrical switches in the door latches can fail, causing the door locks to rapidly actuate up and down multiple times when the locks are activated by either the keyless remote or door lock switch. The affected door latch should be replaced to correct this concern.

It is not uncommon for the power steering rack to develop a fluid leak requiring replacement of the rack assembly. Loss of power steering fluid may also cause an abnormal noise and damage to the power steering pump.

The tailgate latch may stick causing a drain on the battery while the vehicle is parked.

On vehicles with airmatic suspension, the airmatic pump relay can stick, causing a dead battery, because the pump continues to operate when it should be shut off. Eventually, the pump will fail; the pump, fuse, and relay will need replacement. After parking and exiting the vehicle, the airmatic pump should only run for a few seconds before turning off. It should not come back on until the driver's door is opened.

A problem with the ball joints can cause a creaking noise. There is an updated part to remedy this problem.

A no start condition may develop due to an anti-theft system fault. If the drive authorization module fails to recognize the keys, the engine will not start. In many cases, a new module and keys will be needed to correct this problem.

The camshaft adjuster solenoid (which is related to the variable valve timing system) may fail or timing chain/balance shaft components may wear, resulting in illumination of the Check Engine Light and various drivability issues. Mercedes-Benz has released a service bulletin outlining specific repair instructions depending on fault codes stored.

The mass air flow (MAF) sensor tends to fail. The engine air filter should be replaced when the mass air flow sensor is replaced; a dirty filter can allow debris to damage the new sensor.