I've got a rack-damper bolt question that I couldn't turn up an answer to in the search. A little background to the issue might help...sorry for the novel.

My buddy gifted me a 1983 300TD Turbo with 330,000 miles in pretty tired condition as a beater/project car. It runs pretty strong and starts really easily, but soon after I got it, it very suddenly developed a real bad shake at warm idle. Sometimes it's worse than others, but the shake almost never starts before the car is at running temp. It feels a lot like a misfire but goes away the second you get on the gas even a little.

I did some research and tried a diesel purge, changed all the filters and the fuel lines as well as fresh diesel. While this freed up some mid to high range power, it did nothing for the shake. Next I changed the motor and tranny mounts as they were collapsed. I had to skip the engine shocks as I couldn't afford the ridiculously priced bushings, so for now, the car only has one working engine shock. Still, the new mounts didn't help the shake much once it started. I don't think the absence of one shock is the cause of this as it's probably been a decade since this car had them functioning.

Next I decided it would be good to "force" a misfire. So at idle, I cracked each injector line bolt and each cylinder reacted noticeably to the forced-miss. While the shake my car gets does feel like a misfire, it's not as sluggish as a forced-misfire, it feels almost more "productive" if that makes any sense.

I've essentially come to the conclusion this is at worst a bum cylinder and at best a valve job/injector rebuild. Neither of which I have the money to buy the parts/tools to do currently. So in lieu, I decided to mess with the ALDA which someone had clearly bypassed and taken the fuel enrichment nut cap off of. I richened up the fuel and it seems to have helped a bit with the shake as well as freed up low end power. The car hauls ass now!

Lastly, I adjusted the rack damper bolt. First I adjusted it out, and noticed the idle shake got awful quick, so I started to screw it back in. As I screwed it in, I very quickly realized that it had been set all the way in originally! From my understanding, the bolt should not need to be all the way in. I'm curious if this is a sign of a dead rack damper bolt? I've included a picture. I still think this is probably a compression or injector issue but I really noticed the engine smooth out as the bolt went in. I'm driving it now with the bolt all the way in and it drives great and starts very easily. Still, while the shake seems to not come as hard, often or frequently, it hasn't fixed the issue. I've included a pic below.

Also, on another note, a lot of black engine oil came out with the rack damper bolt, is it normal to have engine oil in that part of the IP?

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I haven't noticed the engine shocks do much about the shaky idle. Some here speculate they were more to damp the shut-down shake. No need to buy a $95 top mount. Just scrape out the old rubber and fill w/ black polyurethane caulk (for gutters) like I did.

It is said that the later rack damper bolt (gold?) in say a 1985 works stronger. I swapped one in once and didn't notice a difference. My experience is similar. If you screw it out almost all the way, you notice an increased shaking, but going in a bit you get all the effect you will see pretty early. You might find a thinner jam nut to allow screwing it in a little more, but I doubt it would help. Yes, there is oil inside the injection pump. Put a tiny clear filter on the vacuum line to your "stop valve" so you can see when its diaphragm fails, before you suck that oil all the way to the key switch where it drips on your foot.

First step - adjust the valves. These cars have "solid lifters", not the "hydraulic" self-adjusters on most engines, and need periodic adjustment. Ask anyone who has a pre-1980 Chrysler "slant six". If a valve isn't closing fully, you won't get good compression.

One guy here will test and rebuild your injectors cheap, if you can afford the down time. I don't think the pop pressure matters as much as having a good spray pattern. I found 3 of the 5 in my 1984 were 1600 psig non-turbo ones, but swapping them didn't noticeably change how the engine ran.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Thanks for the input! I can' tell if my rack damper is old or new, looks to be silver to me. I think that this is a valve/injector issue too. I don't doubt my compression is tired on this car but this issue literally started suddenly as I was slowing down for a light out of the blue.

Also, great tip on the engine-shock bushings! I still can't believe that no one is doing an aftermarket option on these, it's such a high wear item and there's literally nothing to them!

"I've essentially come to the conclusion this is at worst a bum cylinder and at best a valve job/injector rebuild. Neither of which I have the money to buy the parts/tools to do currently."

The Valve and Injector issues are the most likely. Adjusting the valves and rebuilding the Injectors with new Nozzles too away 85% of My hot Engine shaking issues.

The original Bosch Nozzles have a tiny drilled passage in the center of the tiny protruding tip and anther passage up further drilled a cross. On the whole set of Injectors removed from my Engine every Nozzle has those passages plugged solid with carbon and it was the same with most of the Injectors I pulled at the Junk Yard.

I think once they are plugged no diesel purge is going to flush the carbon out.

Replacing the Motor and Transmission mounts and fixing a small air leak fixed all but a tiny bit of abnormal shaking. After all of that was done the New Rack Damper Pin was able to remove a little more sake.

This is likely going to be spelled wrong but do a search for polyurethane. You can remove the trashed rubber from your shock mounts and use the Polyurethane to fill in where the rubber was. Several People have done that with Motor Mounts and other items.

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84 300D, 82 Volvo 244Gl Diesel

Thanks! I had a feeling that after I took possession of the car and gave it it's first daily driving and Italian tune ups in quite some time, I knocked something loose and one of the injectors got clogged up, causing the sudden start of the issue.

I'm in the process in saving up for a compression test kit as well as valve adjustment tools and instructions from a certain web-site. Once I get this and check the overall health of the engine, then I'll consider changing the injectors. Due to this car's condition (ridiculously awesome 2-tone taxi style paint job, dead climate control system with no fans, torn up interior and tons of oil leaks all around as well as a huge amount of steering box play), I'm trying to only install things that can be taken out and used on a new W123 in better condition when this car decides to book a 1 way ticket to the junk yard.

How about some pics of the car.

https://instagram.com/p/4UfuAOqeq4/?taken-by=dude_nice_benz


Yes, those are storm trooper masks painted into the quarter panels...

I like the blue!, though I assume it's not an original color?

She looks nice, but man she needs some bundt wheels!

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"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)

Thanks! No, it was a dark blue originally, the paint was pretty atrocious and all the molding had started to come off so the original owner decided to use it to learn how to paint a car. I would love to put some bundt rims on it with some white-walls, it has the original bundt spare tire too. At least it has Mercedes rims on it though, I'm sure I'll be able to trade these. The grill also used to be perfect too, till some ass-hat rear ended me trying to park.

Saddly, the aesthetics are the least of my concerns, but it's great to have a W123 I paid $0 for that I can cut my teeth on under the hood.

Yep, bundt with white-wall tires look nice. That's what Betsie's got.

Guess who has a whole set of original bundt wheels that he has no purpose for?...
Though I'm sure shipping from Alaska will be killer...

__________________
"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)

Re: Rack Damper Bolt

When I first got my 84 300d, the engine had a violent shake only when warmed up and when coming to a stop idling in gear. I checked/changed all the usual suspects (purge, valve adjust, motor mounts) and these helped the shaking only very slightly.

Finally, found on here about the rack damper bolt. I screwed it in all the way, which amounted to about a half turn. Shaking was instantly gone and hasn't been back since. I have the old silver type. The spring was obviously worn.

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'82 300TD
'84 300D OM617
Auto to 4spd Manual Swap 716.210
'85 300SD 2.88 Diff (Direct Swap)
W140 HD Rear Springs w/ bilstein shocks (SLS Delete)
'83 300SD Big Brake Booster Swap
Late model 240D Manual HVAC Swap
W124 Outside Temp Gauge
Aftermarket Keyless Entry

'84 300D RIP

Oh yeah, rack damper bolt. I have another success story. Betsie used to violently rock from side to side as well. Sitting at a traffic light would literally get me motion sick, and I'd have to put her in neutral and raise the RPM's slightly with the pedal to smooth it out.
Sometimes she would idle smooth, but mostly she was shaking like a turd. Embarrassing; folks sitting behind me could definitely see the car rocking. When rocking that bad it also sounded like she had a knock. It sounded a looked horrible.

I went through the "change engine and tranny mount" and all that stuff too...In the end, screwing in the rack damper completely solved the rocking. There isn't even a hint of shaking/rocking when she idles anymore.

So it might make sense to invest in a new rack damper bolt. If you Google them, you can find them for sale: the-site-that-for-unknown-reasons-shall-not-be-named has them for sale. It'll run you about 70 bucks I think, which isn't pocket change, but; if it solves the issue, more than worth it.

__________________
"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)

There is an adjustment that can be made at on top of the Steering Box. The Nut there is really tight and I cannot remember if it is left hand threaded or not.

I had the bad Engine Oil Leaks also and it turned out to be the Valve Cover. I only found the leak after degreasing the Engine and all the way back to the Transmission 3 times. And, then there was still thick dirt and oil left.
After Replacing the Valve Cover Gasket I have lived with the rest of the Oil leaks for 8 years not with no major puddles.

You might want to look up some threads on the MS Valve Adjusting Wrenches. In the past some people had issues with them but I have not read anything within the last 4 years that were negative on them.
Someone on eBay also sells a similar product. Just do a search for Mercedes Valve Adjusting Wrenches.

I live in the LA area and only the Heater and defroster work on mine. In fact none of my 4 Vehicles have working AC and nearly all of the ones I have owned since 1968 had no working AC.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for more great information guys! This rack damper looks to be the old type, maybe I'll pull the trigger this month on the new one, can't hurt and if I junk the car, I can always take it back out and put the old one back in.

Don't junk 'r before she's really dead! Which can take a long time. The W123 is like a cockroach: With half of its limbs missing, it will still plow on.

The steering box play really is not out of the ordinary. When I got Betsie, she had 6 inches (6!) of steering wheel play. Thank God that some previous owner at some point did some suspension work on her, and she tracks perfectly straight, so going down the highway barely requires any steering input. But still, it was no fun.

On top of the steering box there's an adjuster. It's a hex, but I forgot the size. I think it's a common 8mm? Could be wrong. But anyway, much like the rack damper bolt, you loosen up the lock nut (lefty-loosey) and then you turn the adjustment screw COUNTER CLOCK WISE. So the adjustment screw ALSO goes lefty-loosy; you back it out to tighten up the steering.
Yeah, strange but true. Anyway, if you keep a hand on the steering column where it comes out of the fire wall and move it back and forth, you should feel the play get less and less as you adjust the steering box.

Don't get over enhausiastic, and tighten it up all the way. These steering boxes are supposed to have some level of play. One inch of steering play measured at the steering wheel rim is normal.
Me personally I kept it at 2 inches of steering play, because the tighter you make it the quicker you wear out the box, and 2 inches feels like heaven after having gotten used to six.

Also, do your steering box a favor and perform some cheap maintenance on it. Get a power steering filter from this website (couple of bucks) and get some power steering fluid from your local cart parts store. Get like 2 or 3 quarts.

Then:
1) Steer the car all the way to the left
2) Crawl underneath the car, look up at the steering box. There's a drain plug underneath. Undo it, and drain all the black fluid that's in there now
3) Pop the hood, open up the power steering reservoir
4) Undo the little nut that's in the middle and pull the tube-thingy out. Careful, it has a powerful spring behind it, don't let it jump up into your eyeball. Now you can remove the old power steering filter that's at the bottom. Put the new one in, put the reservoir thingy back together, but leave the screw lid off.
5) Put in new power steering fluid. Fill it all the way up. Looks nice and clear, doesn't it?
6) Jack the car up underneath the front cross member (right behind the oil pan). Getting the front wheels a tiny bit off the ground is all you need.
7) With the front wheels in the air, steer the car all the way to the left and right a couple of times. You'll hear gurgling noises. This is the air escaping out of the steering box.
8) Walk to the front of the car again, and check your power steering fluid again. It is probably pitch black again.
9) Drain all fluid. Rinse and repeat until it stays clear.

Now, some folks will tell you that you need to use transmission fluid, because that is what's in the manual; but the numbers for the power steering fluid and the transmission fluid are actually different, so I don't think Mercedes actually literally meant transmission fluid. Transmission fluid has friction enhancers, and I read a theory that said these W123 steering boxes wear out so frequently, because of the transmission fluid being used in them.

So I personally use normal, clear power steering fluid. Again, your choice, on an old car with a worn box it probably won't matter much anyway.

__________________
"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)