Motor mount R&R 1990 300D 2.5 Turbo-138k - PeachParts Mercedes-Benz Forum

2.5Turbo · #1 01-26-2011, 10:18 PM

I finally got around to replacing my motor mounts today. Last fall I noticed a oily fluid that smelled like tire rubber dripping under the car. It took a while for me to probe around with a screwdriver and find the big crack that had formed in the side of the driver's side motor mount. I had been feeling more and more of the engine especially at shutdown, so two and two added to needing new mounts.

I finally got around to it today after getting higher priority items like the leaking DV seals, bad lifters, glow plugs, and a new style vacuum pump done first. I'm sure the leaking diesel contributed to it, but the driver's side mount was totally trashed (new one on the right for comparison)...

The passenger side mount hadn't leaked yet, but it was noticeably shorter than the new one. The top bolts were a little bit of a pain...a number of extensions and a U-joint were needed to get enough clearance for the breaker bar. Even needed to use a cheater pipe on the 18" bar to break 'em loose. They made quite a crack when they broke loose...for half a second I thought I broke the head off the first one. The bottom allen head bolts weren't nearly as bad, came off pretty easy with the 1/2" ratchet.

Now it's running as smoothly as it should...no more vibrating rear view mirror

winmutt · #2 01-27-2011, 09:05 AM

They all compress like that. I think when they are still good they are supposed to pop back. It sure does make a difference. I was told there is a 13mm clearance check. Get something that is round and 13mm and run it between the cross member from one mount to the other. If it gets stuck, you need new mounts. Never tried it though.

vstech · #3 01-27-2011, 10:12 AM

on the top bolt, I recommend a GOOD impact wrench. my old IR 550 would not do it. I had to get a new 900FP from harbor freight. popped em right out. I can't imagine trying to do it with breaker bars!!!

babymog · #4 01-27-2011, 06:21 PM

I did mine with a box-end, ... on two cars. Just takes a little adrenalin and some good gloves to protect the knuckles.

lee polowczuk · #5 01-27-2011, 06:31 PM

Quote:

Originally Posted by babymog

I did mine with a box-end, ... on two cars. Just takes a little adrenalin and some good gloves to protect the knuckles.

you did the drivers side with a box end....??? congrats.... my younger son was able to do it as well...

i had to spend money to get the drivers side done.

Oldwolf · #6 02-11-2011, 10:25 AM

How do I measure the height of the mounts to determine if they need replacement? I get a lot of vibration when I shut down the engine. Thanks.

winmutt · #7 02-11-2011, 10:28 AM

The FSM specifies sticking a 13mm diameter round object between the lower edge of the top part of the mount and the cross member. Never done it but it looks simple enough.

Oldwolf · #8 02-11-2011, 10:34 AM

Sounds simple, I agree. Do you have the FSM # so that I can look it up. I've looked around the FSM but haven't yet been able to located anything about this.

chazola · #9 02-11-2011, 11:12 AM

a finger makes a good gauge- if you can get your fore/index finger in the gap then they're ok (unless you've got really fat fingers of course...) Make sure you check the side nearest the engine. Recently changed one of mine that was knackered after failing the finger test (I had loads of vibration at idle)