2006 Mercedes-Benz C350 4MATIC Problems

RepairPal has identified the most common problems with the 2006 Mercedes-Benz C350 4MATIC 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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24
Known Problems

The 2006-2012 Mercedes Benz C350 4matic 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 engine in the C350 4Matic is known by Mercedes Benz to have issues due to a poorly manufactured gear on the balance shaft (also known as the counter-rotating assembly). Since the balance shaft gear is driven by the timing chain, which keeps the engine rotating synchronously, when it fails, the timing of the engine will change causing:

-Illumination of the Check Engine Light

-Rough Running Conditions

-Stalling

-Loud Rattle or Slapping Noise

-OBD Trouble Code P1200 and P1208

Correction for this issue is replacement of the balance shaft, or balance shaft gear. Replacement of the timing chain and tensioner should be done as well. The Mercedes Benz dealer may cover some or all of the repair cost on select vehicles as a result of a class action settlement.

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 2005-2010 Mercedes Benz C350 4Matic. 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.

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 crankshaft position sensor may fail. Symptoms of this are: The engine will crank—but not start—especially when the engine is warm. The car may start again if it is left to cool off, but it may run roughly or have poor performance. Communicating these specific symptoms to your technician can save diagnostic time.

Failed spark plug wires and/or ignition coils can cause intermittent misfires (rough running); the Check Engine Light may also illuminate. Diagnoses of the ignition system will be necessary to determine which components are at fault.

Catalytic converter failure is common and may cause a Check Engine Light to illuminate.

The mass air flow sensor tends to fail causing poor fuel economy and Check Engine light illumination. 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.

The sway bar end link joints may wear and cause a knocking noise over bumps. Loose or warn links should be replaced to correct this type of noise.

A knocking noise from the upper front strut area can be caused by the hold down nut for the strut coming loose and can be repaired without removing the strut assembly.

A dead battery can be caused by a faulty seat control module that does not properly shut down.  Spilling liquids on the front seats can cause these modules to fail.

The SRS (airbag) light can come on if liquids are spilled into the seat belt buckles, or if the liquid pools underneath the seat and gets into the electrical connector for the seat belt pretensioner. Damaged components will require replacement to restore proper airbag operation.

The heating, ventilation and AC (HVAC) heater box is susceptible to mildew buildup. This can result in a musty odor from the HVAC system, most noticeable when the system is first turned on.

High mileage or older vehicles commonly develop leaks from the differential seals and/or cover. Our technicians recommend a complete reseal of the differential unit whenever these leaks are repaired.

It is not uncommon to encounter premature failure of the anti-lock brake system (ABS) modulator assembly due to dirty brake fluid. Our technicians recommend flushing the brake fluid every two years in order to help prevent this problem.