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  #1  
Old 08-25-2003, 02:02 PM
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Join Date: Aug 2003
Location: West Chester, PA
Posts: 18
300E motor mount replacement

I opened the hood on my mint 1988 300E last night and found a brown powdery material all over the passenger-side motor mount and crossmember -- it looks like I'll have to replace both mounts this weekend. Any tips or tricks? I've seen other posts that refer to tons of information on replacing the motor mounts, but I haven't been able to find anything.

I'm planning to order the new mounts from FastLane, and replace them in my driveway. Any suggestions or tips would be appreciated!

Thanks for your help.
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1988 Mercedes-Benz 300E
2008 Honda Pilot
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  #2  
Old 08-25-2003, 09:31 PM
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Location: Joliet Illinois
Posts: 309
Replacing Motor Mount

I recently replaced the passenger side motor mount on my '92 300E. It was a piece of cake - first I positioned a floor jack under the edge of the oil pan and raised the engine up just enough to take some of the load off the mount. Then I removed the top and bottom nuts from the motor mount and jacked the engine up some more until the motor mount cleared the mounting holes and could be removed. There was also a heat shield attached with a small bolt but I cant remember if that had to be removed before or after the mount was out of the car.

My motor mount looked okay but the car had an annoying vibration at idle. Replacing the mount made a world of difference and it feels like a new car now.

John
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  #3  
Old 08-25-2003, 10:21 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
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Driver's side is a pain to reach -- you will probably have to jack the engine up some just to get the top bolt loose. Passenger side is easy.

Be carefull putting the bottom bolt back in, there is a hole in the crossmember where it can fall in if you fumble it. Took forever to fish it back out with a magnet.

Get new clips and screws for the encaspulation panel, they are cheap and the old ones are probably shot.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #4  
Old 08-25-2003, 10:31 PM
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Location: Jax, FL
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If you jack up the engine...

use a piece of wood across the oil pan and loosen the fan cowl before you break anything at front.
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  #5  
Old 08-26-2003, 01:49 AM
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Location: West Chester, PA
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Smile

Thanks for all of your help! I may be able to get away with only replacing the passenger-side mount for now, but I'll probably end up doing them both while I'm down there. I'll definitely use some wood to brace the oil pan, and I'll check to make sure everything is clear before I brace the motor with my floor jack.

I'm looking forward to seeing how the car behaves with the new engine mounts -- I've been hearing a lurching noise for some time now, and I think this may fix it. I had thought it was from the struts, but they were replaced a few months ago and the noise persists... I'm hearing it more often now that one of the mounts gave out.

Again, thanks for all of the advice. I'll post again once I'm finished to let you know how it worked out.
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  #6  
Old 09-19-2003, 12:26 PM
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Location: Knoxville, TN
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I have a 93 300E and I'm interested in replacing my motor mounts as well. Do you think it is the same as the 92 300E in this tread? I haven't even looked yet but how many motor mounts are there? and what parts would I need to purchase?

Any more tips or tricks you can think of?

Thanks,
Chris
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  #7  
Old 09-19-2003, 12:39 PM
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Location: Dallas/Fort-Worth
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There are only two motor mount to deal with, and the driver's side is a bit more difficult to do simply because of its tight confines. The crossmember has an access hole to get at the lower driver's side lower bolt (or nut, I can't remember). Because of this, if you drop anything during install or deinstall, you run the risk of parts rolling into the crossmember hull...then it's bolt fishing time!

I usually duct tape around the area so as not to offer another path for parts to escape!

In either case, you must raise the engine slightly (the wood plank across the oil pan is a good tip as it relieves the stress and weight of the engine from being concentrated on the jack point). Makes the mount swap easier too.
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  #8  
Old 09-20-2003, 12:22 PM
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Replacing motor mounts

Be very careful while lifting the engine with a wooden block under
the oil pan. The pan is aluminum, can crack very easily.
If you have access to engine hoist, that is the best and safest.
Good Luck
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  #9  
Old 09-20-2003, 11:06 PM
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I'll tell you what! If you had a Mercedes mechanic that works for $49.00 per hour would you let him do your motor mounts for you or would you tackle it yourself? So far this guy has been fair and honest. Thanks guys.........Chris
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  #10  
Old 09-21-2003, 12:41 AM
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Motor Mounts

I personally would liek to do it myself because I enjoy it but more importantly I know it is done right. Also, in the process I learn a lot. Sometines, it is not the hourly rate but also if the mechanic has proper tools to do the job or else you will have another expensive repair down the road.
I torque doiwn all the nuts and bolts as per spec which generally most of the mechanics do not bother.
Many mechanics would not bother to lift the engine with the hoist but would lift it by the pan which is quite dangerous cracking the pan even with the wooden block because of the weight of the engine. Sometimes the crack is not immediate but has fatigued the aluminum where it develops gradually with time.
Anyhow, there are many good and honest mechanics.
Above all, one has to have the time and patience. I have 5 cars, so I can afford to take my time.
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  #11  
Old 09-21-2003, 08:56 PM
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Join Date: Jan 2003
Location: MA
Posts: 114
Re: Replacing Motor Mount

Quote:
Originally posted by John Plut
I recently replaced the passenger side motor mount on my '92 300E. It was a piece of cake - first I positioned a floor jack under the edge of the oil pan and raised the engine up just enough to take some of the load off the mount. Then I removed the top and bottom nuts from the motor mount and jacked the engine up some more until the motor mount cleared the mounting holes and could be removed. There was also a heat shield attached with a small bolt but I cant remember if that had to be removed before or after the mount was out of the car.

My motor mount looked okay but the car had an annoying vibration at idle. Replacing the mount made a world of difference and it feels like a new car now.

I have a vibration at idle on my 92 300E. Is a bad motor mount common? I have 166k on it.

John
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  #12  
Old 09-21-2003, 08:58 PM
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Location: MA
Posts: 114
I'm not using the quote feature correctly. Sorry.

I have a vibration at idle on my 92 300E. Are the motor mounts common? I have 166k on it.
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  #13  
Old 09-21-2003, 09:09 PM
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Location: Evansville, Indiana
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Take a look, it's easy to tell -- the largest diameter "rim" at the base of the steel portion of the mount should be nearly an inch above the frame and dry.

If you cannot see (or feel) the trapezoidal portion at the base of the mount, it's shot.

They aren't exepensive and other than the difficulty in accessing the upper bolt on the driver's side, easy to replace.

A floor jack with a boark on top will work fine -- the bottom of the oil pan is flat and you aren't lifting that much weight. If it still bothers you, make a jig to lift on the AC compressor or the crank balancer instead.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #14  
Old 09-26-2003, 11:35 PM
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Join Date: Jan 2003
Location: MA
Posts: 114
My motor mounts look OK. I've never seen a good one to compare it to, but it has 1" and looks dry.

Do 300E engines vibrate and the mount absorbs it or should I be looking for other problems. I notice it vibrates more when the AC is on. You can feel it on the radiator support. I've heard of cases where the AUX fan bearings can cause vibration.

Any ideas are helpful.
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  #15  
Old 09-27-2003, 12:33 AM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
300E should be VERY smooth and quiet -- shakes can be vac leaks, bad injectors (my next project on teh 300TE), or bad engine mounts (or any combination).

The mounts seem to go every 100,000 miles or so it seems. Having bad ones (that is, empty ones) causes severe vibration because there is a spring in there -- combined mount and vibration damper. Lovely design, does a fantastic job until the glycol leaks out....

Best driveway test is to jack the engine up and check for holes -- the rubber splits next to the steel trapezoid on the bottom and drives up into the body of the mount. In really bad cases (like the TE) the rubber rim at the centerline of the mount will be sitting just above the frame! The 1 - 1.5" clearance is from the bottom of the rubber to the frame, not from the steel to the frame....

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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