Replacing Rack dampener pin - Page 3 - PeachParts Mercedes-Benz Forum

whunter · #31 07-05-2008, 06:53 PM

Quote:

Originally Posted by RML

Thanks for the explanation, Forced. That certainly points to the Rack Damper as the culprit for why my engine shakes at idle. Sometimes it does, sometimes not.

Here is the correct Rack Damper Pin for your engine.

Item Number: 0000742674
Main Category: MERCEDES BENZ
Sub Category: Diesel Injection
Description: diesel injection pump "Rack Damper" adjustment bolt...Rear of Injection Pump

Have a great day.

Diesel911 · #32 07-05-2008, 09:45 PM

On a sticker on the bag mine dampner pin came in is as stated by Hunter part number (Mercedes 000-074-26-74) and inside of the bag is a paper tag with the Bosch part number# 1 420 560 014 000 (the company that made the rack dampner pin).

The things that when corrected had the most/best effect on curing shaking at idle for me: Installing new injector nozzles/tested/balanced and next was finding and fixing an air leak caused by hard fuel hoses down by the primary filter. (Previously the engine shook at cold and hot idle after Injectors fixed cured 80% of that.) (Fixing the air leak cured about 10% more of the hot idle shake.)

Helped but not as much: new Rack Damper screw and new Motor mounts with 1 new engine shock.
The Rack Damper screw by itself had only slight effect and it was hard to find that "sweet spot" where it did anything.
I changed the Motor Mounts many months after installing the Rack Damper Screw. After they were change I re-adjusted the Rack Damper Screw it was easier to find the "sweet spot" and the effect was greater.
My car still shakes just a little more than I would like. I have not yet checked the IP timing and I am hoping that will also have a (+) effect on reducing idle shaking.

JamesDean · #33 08-02-2008, 02:07 AM

question...

and it might be dumb...

should that locking nut be transferred over to the new bolt?

Diesel911 · #34 08-03-2008, 01:35 AM

Quote:

Originally Posted by JamesDean

question...

and it might be dumb...

should that locking nut be transferred over to the new bolt?

Yes.

toomany MBZ · #35 08-03-2008, 07:20 AM

Quote:

Originally Posted by JamesDean

question...

and it might be dumb...

should that locking nut be transferred over to the new bolt?

"O" ring too.

cell · #36 01-17-2010, 07:07 PM

you know, I've read so many threads about replacing the rack dampener pin, that I had just assumed that was the only solution (and I hadn't gotten around to it yet).

well, on a whim I decided to try adjusting mine. and it worked! my shakes are gone! my god, I had no idea this engine was capable of idling that smoothly. and I saved myself $60 too.

so before you replace your dampener pin, try adjusting it first.

300dOwner · #37 03-10-2010, 06:44 PM

Just completed this and whilst trying to tighten up the locknut remembered that my set of (homemade) valve adjusting wrenches were 14mm. They're angled and worked really well at reaching the locknut.

..(my gearwrench was too short to use effectively.)

ROLLGUY · #38 07-23-2010, 08:10 PM

Another thing to remember when adjusting the pin, is to back off on the idle speed adjustment (on the IP between the block and the IP with the 14 mm lock nut) so the governor is acting on the rack damper pin, and not the idle speed adjuster screw.
That would explain why some folks change their rack damper pin, and it makes no change.
Once the idle speed is backed off, the idle quality can then be adjusted with the rack damper pin.
If it is all done correctly, a little resistance should be felt when tightening the pin and idle should smooth out.
Once the pin is adjusted and locked down, the idle screw can be tightened until the idle slightly raises and then backed off a little and the lock nut tightened.
Also, when ordering this part from a dealer or other non-MB specific parts source, they may not have any idea what a "Rack Damper" is.
The correct name for it is "Governor Idle Adjustment Pin" (Bosch and MB name).

JHZR2 · #39 08-27-2010, 10:51 PM

Quote:

Originally Posted by ROLLGUY

Another thing to remember when adjusting the pin, is to back off on the idle speed adjustment (on the IP between the block and the IP with the 14 mm lock nut) so the governor is acting on the rack damper pin, and not the idle speed adjuster screw.
That would explain why some folks change their rack damper pin, and it makes no change.
Once the idle speed is backed off, the idle quality can then be adjusted with the rack damper pin.
If it is all done correctly, a little resistance should be felt when tightening the pin and idle should smooth out.
Once the pin is adjusted and locked down, the idle screw can be tightened until the idle slightly raises and then backed off a little and the lock nut tightened.
Also, when ordering this part from a dealer or other non-MB specific parts source, they may not have any idea what a "Rack Damper" is.
The correct name for it is "Governor Idle Adjustment Pin" (Bosch and MB name).

WOW, this is good info.
Should I then believe that if one was to back off the idle screw far enough, rather than going to, say 300 RPM or not working at all, instead some minimum idle would be maintained by virtue of the presence of the rack dampener pin?
If so, then Ill be sure to back off my idle screw first.

Thanks for that insight!

ROLLGUY · #40 08-28-2010, 10:18 AM

Quote:

Originally Posted by JHZR2

WOW, this is good info.
Should I then believe that if one was to back off the idle screw far enough, rather than going to, say 300 RPM or not working at all, instead some minimum idle would be maintained by virtue of the presence of the rack dampener pin?
If so, then Ill be sure to back off my idle screw first.

Thanks for that insight!

Yes. Although you can try it adjusting the rack damper first, and see what I mean.
It may not make any difference in idle quality until you first loosen the idle speed screw.

JHZR2 · #41 08-28-2010, 03:30 PM

Well I messed with the idle and rack dampener as I fixed my tachometer and wanted to ensure adjustments that I made previously were undone.

No matter how far I pulled out the idle screw, I couldn't get to a point where the idle was supported by the rack dampener.
I didn't get even down to 500 rpm though...
So maybe I didn't go low enough.
However, with the idle screw out a bit so the idle was starting to get rough, I messed with the rack, got a slightly better idle, then took it back to 750.
With my wife in the car we messed with it until there was no shake and the vibration was minimized...

Hopefully next cold start won't be an issue...

whunter · #42 08-29-2010, 01:31 AM

Quote:

Originally Posted by JHZR2

Well I messed with the idle and rack dampener as I fixed my tach and wanted to ensure adjustments that I made previously were undone.

No matter how far I pulled out the idle screw, I couldn't get to a point where the idle was supported by the rack dampener. I didn't get even down to 500 rpm though... So maybe I didn't go low enough. However, with the idle screw out a bit so the idle was starting to get rough, I messed with the rack, got a slightly better idle, then took it back to 750. With my wife in the car we messed with it until there was no shake and the vibration was minimized...

Hopefully next cold start won't be an issue...

The throttle linkage is holding the idle to high = disconnect the rod, and adjust them later.

ChicagoJones · #43 03-27-2011, 12:17 AM

Well a blast from the past... and it just so happened that I was perusing the site today and I saw this.

Rack damper pin replacement did the trick and it still smooth today!

Thanks all.

JHZR2 · #44 03-27-2011, 11:53 AM

Quote:

Originally Posted by ROLLGUY

Yes. Although you can try it adjusting the rack damper first, and see what I mean.
It may not make any difference in idle quality until you first loosen the idle speed screw.

Well, when I loosen the idle speed screw low enough, say below 500RPM, the engine will stall. So something isnt quite right. You cannot necessarily just loosen the idle speed screw and assume that all will be well.

I guess there is a linkage length aspect to it too...

ROLLGUY · #45 03-27-2011, 08:39 PM

Quote:

Originally Posted by JHZR2

Well, when I loosen the idle speed screw low enough, say below 500RPM, the engine will stall. So something isnt quite right. You cannot necessarily just loosen the idle speed screw and assume that all will be well.

I guess there is a linkage length aspect to it too...

I had the same problem, so I just turned in the rack bolt till the idle raised. I also had the case of the shakes on my CD lately, and tried the adjustment on it. I found that it does have the newer style gold bolt, and a very strong spring. No matter where I adjusted it, the shake was still there. I can only assume I have a bad injector. Out of the many rack bolts I have adjusted, my CD and another on an SD are the only two that did not make a difference in idle quality after adjustment.