I'm beginning to think that I have unreasonable expectations. I've only ridden in one Mercedes diesel in my life (my own), so I have nothing to compare it to.

On a car with 150K, is it possible to sit in the drivers seat and not feel any shake at all at idle? I expect there to be a slight vibration, but the shake has me concerned. The engine moves about half an inch side to side with a frequency of around 10 Hertz. Is that bad, or to be expected?

Thanks

Unfortunately with out having driven a new Mercedes of the same year and model you will not have anything to compare it with. After that it is just a subjective opinion.

I believe that the 5 cyl must vibrate less than a 6 cyl even when new. I notice that my 82 6 cyl Volvo diesel vibrates less then the 5 cyl 123.

I had an idea that since my 123 idles smooth in neutral that maybe the Auto Trans was putting some uneven load on the engine while in Drive and causing the shaking. However, one of the Members with a Manual Trans said his also shakes so that killed that idea.
I guess the only way to know would be to install a rebuilt transmission and see if the shaking is reduced.
Due the the heavier weight of reciprocating parts on a Diesel Engine I would guess that the all vibrate more than a comparable Gasoline Engine running at the same speed.

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84 300D, 82 Volvo 244Gl Diesel

Have the motor mounts/shocks ever been replaced? With Ol' Turbo, I feel a very slight vibration at idle with the AC on, but I mean VERY slight. Norm's motor mounts are old, so I feel it a bit more.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

Leadfoot.....from my memory both the 84 and 87 300SD I had produced some vibration at idle that I could detect while seated inside. But you said you can visibly see the engine moving 1/2 inch or so side to side.....I don't recall seeing that much movement in the 5cylinder or the 6cylinder. That much movement from that heavy engine would cause a definite rhythmic oscillation.
Have you had the motor mounts checked?

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

is the car warm or cold, what are the RPMs

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Set the valves. Rocking idle - esp when motor is warm - usually valve lash on 617.

Either that or you have worn or dirty fuel injectors. Do a valve lash adjustment and then a can of Diesel Purge. If it still shakes you may need to have the injectors rebuilt, but before that have them pop tested.

I've already done the motor mounts, tranny mount, engine shocks, valve adjustment, fuel filters, and injector cleaner. I've also replaced the rack damper pin.

What's weird is that the shake is a lot worse when hot, which is what I thought the rack damper pin would fix. Would faulty injectors have a more noticible effect when the engine is hot? I figured a bad injector would make it shake all of the time.

Any help is appreciated. I'm stumped.

Did you find that adjusting the rack damper pin made any difference one way of the other?

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85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60

Not at all. In fact, I was just outside messing with it, and there was hardly any difference with the pin completely removed . I recall that when I adjusted the pin a few months ago, the car would shake violently with the pin adjusted out. Now, it shakes moderately all the time, getting a little worse with the pin removed, and a little more worse when the engine's warmed up.

Is it possible that the fuel rack is damaged?

Thanks for the help.

Shaking worse when the engine is hot is the main symptom. Many times I have spent time trying to figure out why it happens like that but so far cannot come up with an answer.

On mine Rebuilding the Injectors got rid of a higher percentage of shake that the rest of the things I did.
Next was the Valve Adjustment.
I also replaced all the mounts and 1 engine shock. Everything I did helped some.
At the end of it all the Rack Pin (new gold colored) was finally a little helpful in removing some more shake. But fixing the other stuff got rid of the bulk of the shaking.

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84 300D, 82 Volvo 244Gl Diesel

I'm coming to that conclusion myself. I haven't tried a proper "Diesel Purge" by using the Lubro Moly product in a recirculating fashion, but it looks like I can get some at the local Napa. If that doesn't work, new nozzles are next. Doesn't seem like too big of a job. I just need to find the nozzles and a deep well 27mm socket.

Thanks for the advice. I really appreciate everyone's help.

Moving back and forth a half an inch 10 times a second?
That is some serious, FAST shaking. I'd be concerned too.

Mine was shaking and moving about the same distance, but the frequency was more like 3 or 4 Hertz. Adjusting the RDP in several turns seems to have cleared it up though.

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown

My 125k 617 PURRS incredibly consistant and smoothly. Under the hood it hardly looks like its moving. In the car, you just feel a slight vibration. My 300k 617 has the loping rough hot idle. Same symptoms, same travel. replaced everything except the ip (injection pump). From what i hear, thats what causes it. When the ip gets tired, the clearances in the pistons (in the ip) get looser, causing the engine to not recieve as much fuel at idle, causing a rough idle condition. You need a new injection pump, or a good used one. Thats the ONLY thing that will solve this problem.


replacing the ip is on my list of things to do this weekend (getting a good ip from a car im selling in a week )

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1981 300SD 512k OM603

That is NOT what I wanted to hear, but it has been a lingering suspicion.

Assuming I can find a good pump, how difficult is the R&R?

Thanks