I was looking at the passenger side motor mount on my 88 300E and noticed that under the mount on the top of the frame crossmember there is a big "splashing spill mark" of some liquid. It is dried out but I was wondering if these motor mounts are liquid filled and the liquid has been leaked out or maybe it is something totally irrelevant to the motor mounts (maybe some WD 40 that the previous owner spilled). The engine does not have any abnormal vibrations or anything except lately when I start the car at the moment it catches on I feel and hear a momentary brief "thump". Everything else seems fine. Any suggestions?

Check to see how close the exhaust pipe is to the cross member. If the motor mount on that side is bad it will be very close to it and thats the thumping noise you hear.

I just replaced the motor mounts in my 300E. They do not appear to be fluid filled. The rubber in the old mounts had compressed. Before I changed them, they seemed loose, the bolts took 4 or more turns easy. New mounts were not very expensive (PartsShop.com) and only took an hour to install. Put the car on ramps and make sure you have a floor jack handy. Very straightforward. 300Es are a dream to work on. Better than therapy.

Good luck.

Gebhard

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http://www.belmontgroup.com/images/300Ewcolor.jpg

'88 300E 265K
'91 300TE 155K

The motor mount used on W124 and W201 has a built-in engine shock absorber which is filled with ethylene glycol. If the bottom of the metal cover and the subframe is less than 13 mm, replace the mount.

The thump noise you heard may be due to the fact that one side of the engine is momentarily jumping up and down against the subframe. When you start pressing the gas pedal, the defective motor mount is not able to hold down the engine against the torque created by the engine.


David