wicked vibration after motor mount
 

I replaced my motor and trans mounts last night, and when I got in my car to go to work this morning my excitement was replaced with carpal tunnel. I am getting a very noticeable vibration in the body of my car that matches RPM. It feels like the engine is hard mounted to the frame. The old mounts were flat and obviously very old. The old trans mount was just destroyed. I did my valves and timing about a month ago, and there is only a slight oscillation at idle (not matched to the vibration), no visible vibration either (except the fuel/vacuum lines, etc).

The vibration travels through the whole body of the car and makes it horrendously loud, and my whole body is numb after a 10 mi drive.

Do these things need some kind of break in period to soften up? Did I do something wrong? I didn't replace the engine shocks, could that be it?

When I replaced the engine mounts I noticed highway vibration at speed, but it happened at a certain RPM. Below that it would be fine. I did not replace the dampers, but will do eventually. Don't know if that's what's causing it...?

its not the dampeners

Something's obviously wrong. It sounds like you have drivetrain to frame contact somewhere. Not sure how that could happen though. The new mounts serve to put rubber between the drivetrain and frame, so the engine may shake more, but vibrations should lessen, not increase.

Take a good look around the engine. Perhaps the new mounts lifted the engine to the point that something is now hitting where it shouldn't. Another possibility is that one of the bolts that attach the mount to the support arm isn't screwed in all the way, and is hitting the frame. They're easy to cross-thread, and that could cause the problem.

Sometimes when all the mounts are replaced the engine/tranny can get bolted down in a odd position because you've lifted the engine and set it back down. Try loosening the bottom bolts of the engine mounts, and the bolts that hold the transmission to the bracket. Just loosen them a little so there is a little play. Then start the engine and let it idle for a short time and then rev the engine a couple times. Then shut down the car and retighten all the bolts. See if that helps.

X2 ^^^



Also, make sure you didn't cross thread the bolts into the engine arms, it could cause the bolts not seating properly.

You need to look at the instruction in the FSM for adjusting the engine mounts...
MB made it way more complicated ( surprise, surprise ) than just bolting them in..
there is even a special tool they tell you how to make for measuring purposes..

Had mounts replaced on my first W123 by a MB mech long ago when I was too busy to do it myself.

He set the engine back down on top of the windsheild washer bottle when he did the left mount.......vib was amazing. Somethings pinched somewhere. Look around.

I spent most of the morning messing with it, and a little has changed. I think there is rubbing from the top of the trans to the body. That is the only place I can find. I completely removed all of the mounts, and re-attached. The new motor mounts make the engine sit way higher, but not on the hood (get vibe with it up or down). The trans mount also sits higher, I checked and can't even get a finger to the top of the trans in a few spots. I lowered the trans mount what I could, then re-attached. I am still getting the vibe, so I am going out right now to get some washers to lower the trans mount more. I'll report back later. Thanks for the help so far!

Figures with the FSM. I don't have one though. I have been procrastinating getting one for a long time, probably should.

Sounds like alignment.

It was a little strange, the passenger side old mount was much more smashed down than the drivers side. I wonder if that had anything to do with it.

try to recreate it by shaking the engine manualy when its off. Thats how I found my engine noise problem

I was doing that, and getting plenty of play. It was also moving the car. I am starting to get the idea that I just bought crappy mounts and it might get better, it might not. I think I am going to jump in the dumpster in a little bit and get the old ones out. If it doesn't get better in the next few days, I will try to return them.

If you are going to go through the process of removing them again, I wouldn't put the old ones back in. I'd get some OEM ones and put those in instead.

Just curious, where did you get them?