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  #1  
Old 10-14-2008, 07:09 PM
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Rack Damper Adjustment Screw/Bolt - Old vs New

I have an 83 300SD. My engine is having some pretty large vibrations (bad enough to be tearing up my engine mounts pretty quickly) at idle. These vibrations change considerably as the engine warms up.

It was suggested to me to use the Rack Damper Adjustment to minize the vibrations. I guess there is also a New style screw/bolt vs the original.

My questions are:

1. Where is the Rack Damper Adjustment Screw/Bolt?

2. How can I tell the difference between the New style vs the Old?

3. What part do I order (if I need the new style)? (in other words, what is it really called?)

4. Is there a step by step DIY on how to make this adjustment?

5. What am I missing?
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Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")
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  #2  
Old 10-14-2008, 07:58 PM
toomany MBZ's Avatar
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Location: central Va
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1. On the back of the IP, just in front of the oil filter canister.
2. Old one is silver in color, new one gold.
3. Not sure, ask Phil at the "buy parts" button at the top of the page.
4. You re-use the lock nut, 14mm, and flat "O" ring from the old one. Install finger tight, with engine running and warm, turn in or out, 12mm as needed.
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  #3  
Old 10-14-2008, 08:29 PM
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Location: Long Beach,CA
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Quote:
Originally Posted by bigfredb View Post
I have an 83 300SD. My engine is having some pretty large vibrations (bad enough to be tearing up my engine mounts pretty quickly) at idle. These vibrations change considerably as the engine warms up.

It was suggested to me to use the Rack Damper Adjustment to minize the vibrations. I guess there is also a New style screw/bolt vs the original.

My questions are:

1. Where is the Rack Damper Adjustment Screw/Bolt?

2. How can I tell the difference between the New style vs the Old?

3. What part do I order (if I need the new style)? (in other words, what is it really called?)

4. Is there a step by step DIY on how to make this adjustment?

5. What am I missing?
Is there any smoke when this vibration is going on and what color is it?

If the vibrations become less after the Engine is up to operating temperature I would expect that I would suspect something going on in the combustion chamber. Problem Glow Plugs, Injectors.
If vibration gets worse when the Engine is up to temparature it could indicate that the Valves Need to be adjusted.

My car was vibrating after the Engine was well warmed up and not a severely as in your case. I tried the New Rack Damper Pin first and was not happy as it had only a slight effect on the Vibration.

This is what I did to get rid of as much vibration as possible from the one that helped the most on down.
Rebuilt Fuel Injectors (new nozzles,interior surfaces lapped and pop test injectors)

Readjusted the Valves

I changed the oil soaked Motor Mounts, Transmission Mount and replaced 1 Engine Shock (I damaged it while removing it) an put on some used but better condition engine shock mounts.
The above took care of the bulk of the vibration

I replaced the old hard Fuel Inlet hoses that had been causing an air leak; and yes that took away some vibration.

Lastly I went back and readjusted the New Rack Damper pin; this time it was effective at removing a little more vibration.

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  #4  
Old 10-14-2008, 08:33 PM
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also the Rack Damper Bolt is to the rear of the IP and points to the rear near the middle. As the other member said it is the only on that has a Bolt/nut together.
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  #5  
Old 10-14-2008, 08:42 PM
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Quote:
Originally Posted by Diesel911 View Post
Is there any smoke when this vibration is going on and what color is it?
No smoke.

Quote:
Originally Posted by Diesel911 View Post
If the vibrations become less after the Engine is up to operating temperature I would expect that I would suspect something going on in the combustion chamber. Problem Glow Plugs, Injectors.
If vibration gets worse when the Engine is up to temparature it could indicate that the Valves Need to be adjusted.
The vibrations pretty bad on start. They get slightly worse around 50degC. Then get better as it gets up to standard operating temp.

Quote:
Originally Posted by Diesel911 View Post
My car was vibrating after the Engine was well warmed up and not a severely as in your case. I tried the New Rack Damper Pin first and was not happy as it had only a slight effect on the Vibration.

This is what I did to get rid of as much vibration as possible from the one that helped the most on down.
Rebuilt Fuel Injectors (new nozzles,interior surfaces lapped and pop test injectors)

Readjusted the Valves

I changed the oil soaked Motor Mounts, Transmission Mount and replaced 1 Engine Shock (I damaged it while removing it) an put on some used but better condition engine shock mounts.
The above took care of the bulk of the vibration
Replaced the Motor Mounts and engine shocks in April. One motor mount is in mint condition. The other mount is torn-up (no oil or fuel degredation). It looks like perfect rubber, just torn up at the top. (I am in process of replacing it)

Quote:
Originally Posted by Diesel911 View Post
I replaced the old hard Fuel Inlet hoses that had been causing an air leak; and yes that took away some vibration.

Lastly I went back and readjusted the New Rack Damper pin; this time it was effective at removing a little more vibration.
Thank you very much for the info.

Any other suggestions?
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Big Fred

(RIP Sept '10) 83 300SD Turbo Diesel (aka "Rocky")
(RIP April '10 - Accident) 86 Chevy M1009 CUCV (Blazer) - 6.2L Diesel (aka "Ogre")
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  #6  
Old 10-14-2008, 10:16 PM
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I cannot see anything specific to target to look at.

Since I keep extras on hand I would try changing the fuel filters and running the fuel inlet hose into a clean container with clean diesel fuel. I think that would rule out any problems to the rear clogged filters and reduces the places where air could get in. This may not seem logical but it tells you what is not the problem.

Next I would check the Glow Plugs even if I was doing it again just to rule them out as a source of the problem.

I am also thinking of a fuel supply problem and maybe the Fuel Supply Pump on the side of the IP is not working well; that reminds me that the Hand Primer on the Fuel Suppply pump can be a big source of an air leak and it is cheap to replace. (If you think the old filters and hand primer are OK put them in a ZiP Lock bag and save for later.)

While the Engine is running try opening 1 Injector Hard Line Nut at a time and see which Injectors do not make the Engine run worse. If you open a Nut and nothing happens you have a prblem with that Injector or in that Cylinder.

Just to see what would happen I would try pumping a lot on that hand primer before starting and open some of the Injecor Hard Line nuts and bleed it good. Tighten the nuts and start up and see if it runs better for a short period.
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  #7  
Old 10-15-2008, 12:17 PM
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I had a really bad vibration from disintegrated motor mounts. The engine was basically sitting on the frame. I ordered a new rack damper pin at the same time as the mounts. After installing the mounts, the vibration went away, but then the engine had enough freedom of movement to shake side-to-side. Not much, but more than I'd like. Thinking that is the precise symptom of a worn rack damper pin, I installed the new one - no difference. The spring is much firmer on the new pin, but the old one didn't seem too bad.

On both the old and new pin, I get the best results from screwing them in all the way. I've read that this can make it difficult to start the engine, but I have no problem with that. I'm not sure what this means.
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  #8  
Old 10-15-2008, 01:51 PM
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It probably would be best to repair in this order:

Motor Mounts
Valve Adjustment
Fuel System (Filters, check injectors and/or purge)
Rack Dampner

The reasoning is that replacing the rack dampner pin will seem to have little/no effect if the first problems aren't taken care of first. The symptoms of the rack dampner is a rocking/loping of the engine after being fully warmed up. When I saw this was after a highway run and coming to a stop light.
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84 300SD 350K+ miles ( Blue Belle )
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  #9  
Old 10-15-2008, 02:39 PM
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Quote:
Originally Posted by theo3000 View Post
I had a really bad vibration from disintegrated motor mounts. The engine was basically sitting on the frame. I ordered a new rack damper pin at the same time as the mounts. After installing the mounts, the vibration went away, but then the engine had enough freedom of movement to shake side-to-side. Not much, but more than I'd like. Thinking that is the precise symptom of a worn rack damper pin, I installed the new one - no difference. The spring is much firmer on the new pin, but the old one didn't seem too bad.

On both the old and new pin, I get the best results from screwing them in all the way. I've read that this can make it difficult to start the engine, but I have no problem with that. I'm not sure what this means.

I would take a look at the Rear Transmission Mount. If the Motor Mounts disintigrated this left only the Transmission Mount to hold on to the Engine and deal with the Engine tourque.
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