My engine (om617) in my 300sd shakes excessively at idle. It looks like the engine is rocking left to right and is going to rip the motor mounts. I just put in new motor mounts, trans mount and did a diesel purge. I am going to do the valves tomorrow.. The engine shocks are shot but I dont think they could be the cause of all this shaking. If I ever so slightly press on the throttle, it runs as smooth as butter.... Any ideas? Maybe I can adjust the rpm a little bit higher? could it be anything else?

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Do a search for rack dampener screw

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Do the valve adjustment first, especially if you don't know if/when they were done. You may be pleasantly surprised. I know I was.

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Sam

84 300SD 350K+ miles ( Blue Belle )

My 82 SD shook really bad until I had the valves adjusted. Good luck

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1989 300E
103,500 miles

1982 300SD
Sold but not forgotten

same thing here! Help!

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1981 300SD 512k OM603

Also, look for bubbles in your primary filter or wet fuel lines. My engine shook until I cleared up my fuel leaks.

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

ok did a valve adjustment and god were they tight!! it is running a little better now but still rocking a little bit. I pulled the rack damper screw and it was the 'silver' one but the spring was still firm. I backed the bolt out and it started shaking really bad.... as i tightened it in it reduced the shaking but only a little bit.. should i go ahead and replace it?

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Maybe, if this continues to happen AFTER THE ENGINE IS AT OPERATING TEMP. If it shakes when cold, the problem is elsewhere.

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83 SD

84 CD

car shakes only when hot for me, How can I tell where air is leaking into my system, if air is leaking into my system. The thing is that the car that this engine was in, when the car was totaled, didnt shake like this. I ran it and stuff before the swap and it didnt shake. After I swapped it in it shakes now. So i dont think its low compression on a cylinder, all valves are good I checked. I replaced the nozzles, now it has more power but still shakes.


new motor mounts.
Ive tried the dampner bolt from my low mileage car, no difference.


Before I put the motor in I did open up those banjo bolts on the fuel system as I was looking at the sizes of the banjo bolts. I basicaly took apart the system of brown lines and banjo bolts on the secondary filter. I did not replace the crush washers, I just used them again. Can you use them again, I mean, why not? Its just a piece of aluminum. Also the infamous fuel filter leak, I have that leak becuase Im to lazy to go find a crush washer that size, can this be letting air in my system? My leak isnt that bad, its just kinda wet there. Also you know those brown lines, when you rev the engine you can see a stream of bubbles go though them, then it clears. But I dont think thats a problem, my 85 does that too and it idles like a gasser. Also I have this other problem that I think has to do with air being in the lines. When i cold start the car, sometime it will stumble. Not just immedietly afterward, but sometime a few seconds, or ten seconds after i start it. it seems to miss randomly, maybe a few misses in a ten second period. Also new glow plugs. But its not that, i mean the engine can cold start in 50 degree weather with no glow plugs in about 5 cranks. So yeah, im thinking air in the system. Where do I start. This is pissing me off, ill be in traffic and the car is literaly rocking back and forth.

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1981 300SD 512k OM603

Don't be so quick to discount the effect of the engine damper on vibration at idle. I always thought they were primarily for reducing vibration during shutdown but I was surprised to find how effective replacing mine was in curing a hot-idle vibration problem with my 240D.

When I removed the old one it was clear that it was completely worn out. The new one, while it didn't eliminate 100% of the vibration did damp out at least 80-90% in my opinion and was well worth the effort...so...when you have exhausted all of the other options try replacing the damper(s).

I believe my hot idle vibration is possibly caused by low compression in 2 cylinders and will never be cured without addressing this which I am not going to do at this point, but before replacing the damper my whole car would shake like a paint mixer and now it hardly does at all.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

One thing is important is that most people don't even bother to look at the rear of the car. Namely the hose that connects to the fuel tank. After 20 or so years, they can rot/harden and develop slight air leaks. Since you are there you should look into changing out the tank screen. No doubt it should have some gunk in it to restrict fuel flow.

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1983 123.133 California
- GreaseCar Veg System

What helped on mine was the initial valve adjustment (very tight also), running it 100-200 miles then another valve adjustment. (A hint I picked up from the forum.) I was very pleased at how smooth the idle became.

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Sam

84 300SD 350K+ miles ( Blue Belle )

That was my problem - cracked leaky fuel lines, loose primary filter bolt, loose hose clamps at each joint. Car would start up just fine, then get rough. If I adjusted the idle way up, or gave it some throttle, I could overcome the problem - probably by drawing enough fuel to compensate for the air. Once I got the leaks tracked down all that was magically gone.

As the earlier poster said, also check the lines at the rear end - they may be wet, too.

Not really rocket science, just trace the lines and make sure that each section of the fuel system is dry and tight.

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

+1 to a fuel system air leak - that made a big difference on mine (from fuel filter bolt).

I also replaced my rack bolt, that made a small difference too. I had the silver one to start.

I have heard, but have not verified firsthand, that micro-cracks in the clear plastic hard fuel lines can cause this type of air leak.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

valves done, new mounts, fuel filter bolt tight, new fuel filters, no air bubbles in primary fuel filter.. still got the shakes... my rack bolt is silver -- could this be the problem? The spring still seems firm though.. if i unscrew the damper bolt the motor starts shakin like crazy and with the damper bolt tightened all the way in it reduces it but it still shakes a little bit.. also it seems like the engine has the 'hiccups' when i first start it. i have to gas it to smooth it out... any ideas??????

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