How long do OE motor mounts usually last? - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 08-28-2010, 02:55 PM

On a 603. Just curious. After replacing the front tires on my 87 300D, my neverending highway vibration reduced quite a bit (and the noise is gone!), but I'm definitely still getting a shake in the steering wheel and slight vibration in the floorboard, intermittently between 55-70. It seems to be most noticeable on acceleration, and is (in my nonscientific estimation) more often to occur while going up a very slight incline.
I noticed some very tiny cracks in the motor mounts and I'm wondering if it could be them starting to go? They were replaced 50,000 miles ago (five years). The transmission mount, as far as I know, has never been replaced, so I'm going to do that. Would it be wise to do the motor mounts while I'm at it, or a waste? For whatever it's worth, idle and low speeds are super smooth.

As a side question ... the rear linkage on this car is a disaster, and the diff bushings (in the back, that hold it on the subframe) are shot. I plan to have my indy do that job when I get back from London in the fall (technically I can do it, but physically I don't think I can by myself). Can those problems in the rear manifest in vibrations in the front?

Poor Bodhi, this has not been his year.

Guess it could sure be worse. At least I've gotten some things solved along the way.

vstech · #2 08-28-2010, 02:58 PM

I can't see motor mounts causing a vibration in the wheel that's not felt at idle.
how smooth is your acceleration? it could be the trans mount allowing the motor to tilt down on a hilly climb though. start there and see. if your rear bushings are SHOT then all manner of issues could be felt...

jonbobshinigin · #3 08-28-2010, 03:52 PM

Go for the transmission mount...that is an easy job. The mounts are not likely bad after just 5 years and they collapse when bad. The rear bushings (multi-link arms) are significant in tracking at high speeds. As for subframe mounts, I have not done mine yet but at 185k or so, they SEEM to be okay.

aaa · #4 08-28-2010, 04:27 PM

It's a tire or suspension issue.

Jeremy5848 · #5 08-28-2010, 05:11 PM

Engine mounts on the 60x engines are usually good for about ten years, give or take.

sixto · #6 08-28-2010, 05:29 PM

You can measure a gap to determine if the engine mounts are still good -

Sixto
87 300D

BodhiBenz1987 · #7 08-28-2010, 06:21 PM

Quote:

Originally Posted by sixto

You can measure a gap to determine if the engine mounts are still good -

Sixto
87 300D

Looks easy enough, thanks!

Last time I had the mounts replaced there was actually fluid coming out of one of the old ones, so it wasn't a tough judgment call.
I'll start with the trans mount, I have a new one ready to go. I'd like to do the diff mounts if I can get my hand on the tool, too. There's no question they need to go, one of them is sort of half-collapsed.
aaa ... the tires are brand new, at least on the front. I suppose it could be the ball joints or lower control arm bushings, but all look pretty good. It's kind of reaching a point where I'm just replacing things at random and hoping the problem goes away. The tires did make a big difference cruising on the highway, but not completely.
And it could still be steering. And I'm not convinced the lug nuts didn't get damaged by the tire shop I used to go to.
So basically it just comes down to what order to start replacing things, and I'd like to rule out (or in) whatever I can before doing so. I'll pick up a 13mm bolt and hopefully I can rule out motor mounts.

Fulcrum525 · #8 08-28-2010, 06:44 PM

Mine has been shacking too and I have two new transmission mounts sitting in my garage waiting for installation. How hard of a job is it? Would I have to lower the transmission in any way or form?

BodhiBenz1987 · #9 08-28-2010, 07:00 PM

Quote:

Originally Posted by Fulcrum525

Mine has been shacking too and I have two new transmission mounts sitting in my garage waiting for installation. How hard of a job is it? Would I have to lower the transmission in any way or form?

I think the hardest part is getting to the bolt on top, though it doesn't look impossible. You don't have to lower the transmission, just support it with a scissor or floor jack while you swap out the mounts. Haven't done one yet but it doesn't look too hellish ...

Fulcrum525 · #10 08-28-2010, 07:51 PM

Quote:

Originally Posted by BodhiBenz1987

I think the hardest part is getting to the bolt on top, though it doesn't look impossible. You don't have to lower the transmission, just support it with a scissor or floor jack while you swap out the mounts. Haven't done one yet but it doesn't look too hellish ...

It does when you don't have a lift....

Sev · #11 09-01-2010, 01:47 AM

Quote:

Originally Posted by sixto

You can measure a gap to determine if the engine mounts are still good -

Sixto
87 300D

That's only if you have the type of mount which has the metal 'sheath' that extends down to the top line which the arrow in your picture lines up with. there were other kinds of mounts which only had a metal cap on top, and had rubber all the way around (bell-shaped) with no aluminum sheath. where do you measure for those type of mounts, the bottom of the rubber?

BodhiBenz1987 · #12 09-01-2010, 02:34 PM

Quote:

Originally Posted by Sev

That's only if you have the type of mount which has the metal 'sheath' that extends down to the top line which the arrow in your picture lines up with. there were other kinds of mounts which only had a metal cap on top, and had rubber all the way around (bell-shaped) with no aluminum sheath. where do you measure for those type of mounts, the bottom of the rubber?

If I understand correctly the mounts you are talking about, they are shaped the same way as the OE ones ... so you would measure from the part of the rubber that corresponds with the bottom of the metal ... the bottom of the "bell." I could be wrong though, as I'm not really sure I know what mounts you're talking about. Fortunately mine are OE so I used the graphic sixto provided.

Sev · #13 09-01-2010, 03:02 PM

Quote:

Originally Posted by BodhiBenz1987

If I understand correctly the mounts you are talking about, they are shaped the same way as the OE ones ... so you would measure from the part of the rubber that corresponds with the bottom of the metal ... the bottom of the "bell." I could be wrong though, as I'm not really sure I know what mounts you're talking about. Fortunately mine are OE so I used the graphic sixto provided.

the mounts you have which are OE, are the updated style mounts with the aluminum sheath. there are still rubber non-sheathed OE mounts out there with MB part numbers stamped on them. they are circulating through the parts stores and online, and were made by mercedes

BodhiBenz1987 · #14 09-01-2010, 06:20 PM

Quote:

Originally Posted by Sev

the mounts you have which are OE, are the updated style mounts with the aluminum sheath. there are still rubber non-sheathed OE mounts out there with MB part numbers stamped on them. they are circulating through the parts stores and online, and were made by mercedes

Ah, OK. Don't they have a similar shape to the metal-sheathed ones, though?