RepairPal has identified the most common problems for 165 Mercedes-Benz models based on complaints from actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.
The engine in the R350 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
-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.
The Mercedes Benz C350 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 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.
Leaks may develop from the differential cover and/or seals on high mileage or older vehicles. Our technicians recommend a complete reseal of the differential unit if these leaks are addressed.
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.
An exhaust leak may develop due to cracked welds on the front catalytic converter. Replacement of the catalyst is recommended; re-welding of the catalyst is discouraged because it is an emissions device.
Rear air springs (bellows) may develop leaks, which causes the air pump to run more often to maintain ride height. Our technicians recommend that leaking air springs be replaced.
The active body control system can leak fluid from numerous areas, including the tandem pump, hydraulic lines, struts, and/or seals. If it is not repaired, the vehicle ride height could drop too low and cause damage to the undercarriage.
Ball joints can wear out prematurely, causing wear in the tires.
A refrigerant leak may develop from one or more of the following AC components: AC compressor, hose manifold for the compressor, or the evaporator core. The loss of refrigerant can cause poor AC performance. Our technicians tell us that proper leak diagnoses should be performed in order to determine the cause of any refrigerant loss.
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 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.