Replacing Rack dampener pin
 

Did you check your engine mounts, tranny mount and engine shocks?

It is a good idea to replace the original pin with the updated one.

I do not think anything falls out, but I am also curious how to install the new one with out over tightening it.

The mounts were changed a couple of months ago, engine shocks were checked and not flopping around when the mounts were changed, tranny mount is all intact and also did an Italian tuneup. Rack Dampner pin I guess is next.

If you get it from ************** they send directions. But IIRC when I did mine, you get it in there till you feel a little resistance and start the car. If it idles (even rough) get it up to operating temp and start bumping it in until the engine smooths out. If I were to feel significant resistance I'd stop turning it and start looking at other causes for the problem. From what I understand, it's kind of like that ALDA adjustment screw--you really don't want the things inside the IP attached to it to break.

Have you also cracked the fuel delivery lines one at at time to each injector while the engine is idling and note it's characteristics? You should notice a harsher idle. If you crack one and no change, then it's time to do an injector/cylinder swap and retest to rule out bad injector.

Did you also check the operations of the engine shocks? I have seen them look ok visually, but had no resistance when actually moved. The engine shocks should be pretty stiff to move.

Glad to here the mounts are good.

Just did this...
 

You need a 14 mm and 16mm open end wrenches I believe.

-Get the car to hot idle, shut the car off.
-There is a locknut on the old pin. Loosen this a couple turns.
-With the wrench, and then your fingers unscrew the old rack damper pin. A valuable technique: Straddle the oil cooler line with your thumb and middle finger to make the turns. This makes the whole procedure SOOO much easier. I laughed a cosmic laugh when I realized this.
- Remove and observe.
-Take some of the oil off the old pin and put a little on the new gold pin.
-Screw pin into the IP until you feel a little resistance.
-Turn the car on.
-Now it's time to tweak. Back out the screw until the engine really lopes. You'll know when youre there.
-Now screw in a couple turns, to right after it stops loping. It will not get much smoother going in further, it supposedly will be harder to start.

This improved my hot idle quite a bit. I got a gold damper screw off a junkyard car. There's an article that ive probably paraphrased pretty much at mbz.org IIRC.

Good luck!
dd

I failed to mentioned I did that. I even switched injectors around to see if would calm down. As for the shocks, there were some resistance I that though were ok, but I am not really sure what a "new" shock would feel like.

Thanks this sounds good!

I changed mine out about 2 months ago. New ones are nearly impossible to move up and down when they are out of the car. In the car you can move them, but it is hard to do.

My old ones, one was actually broken off, the other had the lower rubber mounts missing. I could move the old ones really easy, even out of the car.

Right on except 12 and 14mm. He's right if you go too far in the car will be harder to start and want to die out until warmed up.

this sounds like it might solve my vibe issue as well.can the spring be replaced without buying the entire new part? where is the cheapest source for the gold rack damper? thanx

No.

Junk yard. A new one is in the $90 range. :eek:

Rack Dampener pin
 

Im new to MB diesels, what is this pin what does it do, why does it cost so much and where is it

How do you know if a used one is any better than the one you've already got? If its gold does it have a fair shot of being worthwhile?

I took one out of a yard car. I wanted one quick. I really have no guarantee that the pin is %100, but its better than my silver one was.

For $27 bucks I think it would be worth it to invest in a new one, ensuring you have a fresh spring.

I think I am screwed, mine will not turn by hand, even after seriously loosening the lock nut.

It won't because the o-ring is acting like a wedge in the threads.

I've spent the last, what 20 minutes fumbling with it... no matter which way I go with the lame, short 12mm wrench, It will not back out...


I hate the rack dampner bolt... I can't get enough throw on the wrench to back it out at all.. Lowes didn't have a long enough 12 mm, they sold one that was shorter than the craftsman I already have! I'm not driving 45 minutes for a bloody wrench that sears probably wont be able to find for me. I'll have my mechanic do it.

Get a gear (ratchet) wrench for about $12. The 12mm gear wrench also makes changing glowplugs much easier.

I got it out without the gear wrench, But I would like some in the usual sizes.

can someone please post a picture of the rack dampner and where it is on the ip.
thanks

Start looking in the space between the IP and the oil filter. It's screwed into the IP, in its rear. Can't miss it.

I was talking to the indy I go to when a job is over my head. He told me it controls the fuel pressure, and if I decide to play with it, mark where it was set so I can get it back there if needed. They set the pressure at the factory. From what I have read, the original pin had a weak spring and the replacement corrects that problem. So it sounds like if you are getting one from the junkyard, make sure it is the replacement. For the price, time invested in getting it from the junkyard, and risk of it being worn out, personally I would go with a new one. I have been burned too many times with trying to save a few bucks at the junkyard on a critical part. Heck, it costs less than a fillup now.

Here is one I found with some info: http://**************.com/search/node/rack+damper

If anyone has had problems with this parts source, please let me know. I looked at Fastlane's parts catalogue first but did not see it listed.

Your Indy is not correct concerning the Rack Damper Bolt controlling the fuel pressure. The fuel injection pressure is controlled by the Pop Pressure of each of your injectors and the pressure from the Fuel Supply Pump is controlled by the Overflow valve on the side of the Fuel Injection Pump Housing.

Well, so much for his opinion. From the shape of it, like a needle valve, it looks like it would control flow of fuel somewhere along the path of fuel delivery.

The rack damper is exactly what its name suggests, it dampens the rack. Its a mini shock absorber that keeps the fuel rack from vibrating at idle and making the engine shake.

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.

A nice big picture would help us newbies,and a part number too,thanks.

Try this link: http://www.peachparts.com/shopforum/attachments/diesel-discussion/42618d1174877713-so-what-does-rack-damper-bolt-617-actually-do-rack-damper-gold-silver.jpg

Try part # 0000742674.
In the pic, the top one, gold color, are the new ones, they have a stronger spring. It does not come with the lock nut, or "o" ring, the latter of which is not on either one.

Here is the correct Rack Damper Pin for your engine.
 

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.

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.

question...

and it might be dumb...


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

Yes.

"O" ring too.

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.

Rack Damper replacement tip - locking down the bolt
 

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.)

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!

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 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...

Answer
 

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

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.

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.

Recycled
 

For new members.
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