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Common Mercedes-Benz Problems
Check Engine Light on? ABS light on? Engine running rough? Here you will find some answers to the most frequently diagnosed Mercedes problems brought into our two repair shops. We do not recommend you assume that the answer here directly relates to your car. Accurate diagnosis of a problem typically saves you money. And, you should know that often third parties will misdiagnose a car for what appears to be similar problems or related diagnostic codes.
Gear Shifter Won’t Come Out of Park
This is a common problem on many E and S class Mercedes-Benz models. The car will start and run, but the shifter even without the engine running will not come out of the park position. This is caused by a failure in the selector module. The signs of wear normally occur a short time prior to the failure – if you experience trouble getting the car out of park anytime, have it inspected asap. Clearly moving the car once this problem has occurred is frustrating.
Cranks But Does Not Start
Many Mercedes-Benz vehicles suffer with this common problem. The engine will crank and crank but refuses to start. The common cause of this problem is the crank shaft position sensor. The engine management looks for the indication of TDC from the crank position sensor. When it does not receive the signal, it does not fire the engine. Commonly, you will experience longer crank times prior to the failure of the sensor.
Rattle At Startup
Some Mercedes-Benz engines will experience a rattle during the initial 15 seconds of running the engine – especially in colder climates. The rattle is often caused by a belt tensioner that has become worn. However, if the rattle continues, the cause can often be a water pump pulley. Left unchecked, either of these situations can cause you be stranded without a belt or over-heating.
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Runs Rough – Check Engine Light is On
There are many reasons why a check engine light would be turned on. Rough running is usually a sign of misfires and therefore there is a need to determine if the misfires are occurring to all cylinders or individual ones. Many times on Mercedes-Benz vehicles, the source of missfires throughout the engine is a failure in the mass air flow meter. The engine management on many vehicles is good enough to have the engine run quite smoothly, despite bad information coming from the MAF. A common sign of a failing MAF is a change in fuel consumption.
Rattle From Rear Suspension
Of course, a rattle at the rear of the car could be any number of things. However, one of the most common on Mercedes-Benz vehicles is a brake in the lower portion of the rear spring. The spring breaks and leaves the lower coil in the rear spring pocket. As you drive the broken pieces rattles. The ride height of the vehicle is affected, but it is not always obvious that this has changed. broken springs should be replaced in pairs and addressed as soon as possible.
Fluid Leak Under Center of Car
It’s common on older Mercedes-Benz vehicles to find a transmission leak near the center of the car – usually red fluid. This can have a number of sources, not least of which is the seal for the transmission pan itself. However, one of the most common sources of this leak is the electrical transmission plug attached to the side of the transmission. the seals in the plug begin to leak and fluid escapes. The leak is normally slow at first and only a few drops will be evident. However, it can speed up and the result of the lower levels of fluid in the trans can be catastrophic.
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V12 Runnability Issues
Some Mercedes-Benz V12 engines develop strange runnability issues. This can show up as failing O2 Sensors, misfires of odd cylinders etc etc. Most of the time this will cause a check engine light and on many occasions will go away when the key is cycled. One of the most common causes of this type of failure is the oil pressure switch. Oil will begin to migrate out of the switch and through the engine wiring harness. Replacing the oil pressure switch solves the root cause of the oil, but removing the oil itself can be extremely difficult without replacing the wiring harness.
Ignition Key Will Not Turn
This is very frustrating – especially on a cold snowy evening. The key will go into the ignition barrel but will not turn. From here you are stuck and hopefully you will have the number for a trusty tow company to hand. The common cause of this issue is a failure in the EIS module. Commonly, this will show signs of wear through difficulty in turn the key a few times before the failure occurs. If this happens, have it inspected before you get stuck.
Front of the Car is Low – S Class
It is quite common for the S-Class Mercedes-Benz fitted with air-ride suspension to have one or 2 corners of the car fail. This results in a lowering of the car, sometimes to a level that makes the car impossible to drive. There are a number of common reasons for the suspension failure from pump to diverter valve block, however, if the problem occurs only with the front of the car and everything else checks to be working, the source of the problem is normally leaking struts. There is a repair kit available to resolve the leaks and it is considerably less expensive than replacing the shocks.