Vibrations and Shaking Inside a Mercedes-Benz Cabin.

Problem: Interior Vibrations

Are you feeling vibrations inside the cabin of your Mercedes? Often, MB owners feel seat vibrations that can’t be explained because the car runs great in most cases. Vibrations may be felt on the steering wheel or dash and are most noticeable when stopped at a red light.

First identify when the vibration occurs. A vibration at idle that becomes stronger in Drive or Reverse while the vehicle is stopped can indicate worn engine or transmission mounts, but a rough-running engine must be ruled out first. Vibration through the steering wheel at road speed is more often related to the tires, wheels, or suspension. Vibration during braking or acceleration requires a separate brake or driveline diagnosis.

Troubleshooting

Are these vibrations more noticeable when your car is in Drive or Reverse?

If you answered yes, you most likely need new engine & transmission mounts. Typically, these vibrations are noticed when your car is in Park or Neutral. The vibrations intensify if you move the shifter in Drive or Reverse but keep the vehicle stopped. In the majority of cases, the problem is the motor mounts.

Checking if your motor mounts are defective is easy, but you need a helper and must be extremely careful.

CAUTION: Make sure no one is standing in the front or back of the car when you perform this test.

Cause

Mercedes-Benz motor mounts are fluid-filled instead of rubber mounts used on most cars. Mercedes-Benz engine mounts start to lose fluid around 100,000 miles. Once a crack develops in the motor mount, they lose all the fluid over time, and vibrations worsen.

Mercedes cars have three mounts. One on each side of the engine and one at the end of the transmission near the output shaft. The transmission mount is not fluid-filled but just a regular rubber mount. The transmission mount can also wear out and require replacement.

Replacing all three mounts is recommended. Your Mercedes will feel like it just rolled out of the factory. Seriously! Even if your Mercedes has 200k miles, once you install new motor mounts, you won’t feel a single vibration inside the cabin. 

Replacing Mercedes motor mounts

Motor Mounts

The two engine mounts are oil-filled. Once you replace these, you will think you suddenly got a new car. Night and day difference between the old mounts and the new ones. These mounts are not that easy to replace. If you have the correct model-specific engine mount wrench or socket, this is also an easy job.

Replacing Mercedes-Benz engine mounts can be labor-intensive. It may require a special offset wrench or socket to remove the top bolt on the motor mount. There isn’t much room to access the motor mount. The engine needs to be raised a couple of inches. The job can take a DIYer 2 to 4 hours. We have put together a DIY guide on how to replace the motor mounts to help you eliminate cabin vibrations.

• DIY Guide: On how to replace Mercedes motor mounts

Transmission mount

The transmission mount is very easy to replace. You raise the car and support the transmission with a jack. Remove the transmission mount fasteners, replace the mount, and torque the fasteners to the model-specific specification. If you change your oil, you can do this too. It is easier than changing the oil on an MB. Here is a picture of the transmission mount, shown upside down, so that you can see the location of the bolts. You can get this mount for less than $20 on Amazon; see here.

Where to Buy Mercedes-Benz Engine Mounts?

The two engine mounts range from $80 to $150 per set. You can get quality ones like these ones, on Amazon for a fraction of dealer prices. These are quality oil-filled mounts.

Depending on the model and engine, a mechanic may charge between $400 and $800 to replace the motor mounts on a Mercedes. The exhaust manifold may need to be disconnected to pull out the old motor mount.

Driving with a failed motor mount is not fun. Driving an old Mercedes with new motor mounts will make you think you got a new car.