Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

LinkBack Thread Tools Display Modes
Old 06-06-2012, 09:18 PM
Registered User
Join Date: Jan 2009
Location: NJ
Posts: 68
'84 300sd Replaced Engine Mounts, still shaky

Hi all,

I had a pretty bad shake at idle. I replaced my engine mounts, one of which was literally in two pieces. When I first started the car with the new mounts, it seemed really smooth. However, I notice now that the car is shaking at idle again- in P, N, D, R, whatever. I tried to change the idle with the rack screw (I have a new one), but I couldn't seem to find a smoother spot with it. Should I change my trans mount? Is there something else I should try first?

1984 300SD. 115k miles.
Reply With Quote
Old 06-06-2012, 09:25 PM
Registered User
Join Date: Mar 2007
Location: Bethel VT
Posts: 119
Sure sounds like rack damper bolt, it'll cause a pretty severe shake at idle (and kill mounts quickly) Did you inspect it or attempt to adjust it?

Otherwise, it may be missing at idle due to some air in fuel or dirty injectors?
Reply With Quote
Old 06-06-2012, 10:07 PM
Registered User
Join Date: Jan 2009
Location: NJ
Posts: 68
I replaced the rack bolt with a new one from peachparts a few months ago. With the engine at idle, I am turning the rack bolt in and out to try to find a spot where it runs smoother. It seems smoothest almost tightened all the way, and when I loosen it more than a few turns, the shaking gets absolutely wild, and the RPMs drop. Now it idles 600-700RPM.
1984 300SD. 115k miles.
Reply With Quote
Old 06-06-2012, 10:22 PM
junqueyardjim's Avatar
Registered User
Join Date: Apr 2005
Location: Cicero, Hamilton County, Indiana about 30 miles north of downtown Indianapolis
Posts: 2,609
I certainly would replace the rear mount if it looks as bad as most of them do.Don't you get some relief from that shake in neutral? You should.
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis

1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!
Reply With Quote
Old 06-07-2012, 01:14 AM
Diesel911's Avatar
Registered User
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 24,828
What I had to do to get rid of the my when Engine hot vibration/shaking:

Raise the Idle speed within the normal range (this helped some; it was around 700rpm). I raised it to about 750 rpms.

I bought a new Rack Damper Bolt but it did not help much. I have a turbocharged 300D Tubo and it has a Rack Damper Bolt.

Rebuilt my Injectors with new Nozzles (This took away most of the shaking)

Doing a Valve Adjustment (took away some more shaking). If you can adjust the Valves yourself do that first except for the new Valve Cover gasket is free.

Changed Motor and Transmission mounts (took away some more vibration)

Found that I had a small air leak that showed up when the Engine was hot due to hard fuel inlet lines that did not seal even with the clamps tight.

Finally was able to use the Rack Damper Bolt to tune out a little more shake. (that bolt was made to reduce the shake on a new engine; not to compensate for a bunch of worn and out of spec parts.
Somewhat the same for the Motor and Transmission Mount.

Do the cheap stuff first.

Long Fuel Pressure Relief Valve/Overflow Valve Thread
Fuel pressure relief valve adjustment
84 300D, 82 Volvo 244Gl Diesel
Reply With Quote
Old 06-07-2012, 01:29 AM
ROLLGUY's Avatar
Join Date: Oct 2007
Posts: 5,908
I would try backing off on the idle speed adjustment screw (back side of the IP) before adjusting the rack damper bolt.
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 06:31 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page