85 CD engine vibration

I'm still troubleshooting a constant vibration. In gear, out of gear, standing still or moving. I have a constant vibratiion beginning at about 1000 RPM and does not go away at any RPM and gets downright noisy at highway speeds. It has a chug-chug sound that can be felt in the ears and the butt. More annoying than anything, but I'm sure eventually things are going to begin to vibrate loose on an otherwise solid vehicle. I've done the following: Changed all filters including tank, replaced injectors, diesel purge, checked turbo, disconnected exhaust, replaced rack damper bolt, adjusted valves, checked timing chain, checked compression. After all that, I started looking at the drive train. Replaced all mounts, checked drive shaft couplings, all was good. I removed the transmission and started the car, vibration went away. Replaced torque converter, still had vibration. Replaced transmission with known serviceable unit, still has vibration. The only time the vibration has gone away, is when the xmission is removed. The flex plate and fly wheel "appear" to be good. I guess I'll have to change the fly wheel and flex plate, but hesitate to pull the tranny again. HELP!!!!!! Anyone out there have any similar experience?

Thanks,
Bob

Forums

Diesel Engine Specific Aid

Chassis Model Number

W123

How long vibration?

Has this vibration always been there since you have owned the car? Any maintenance records or evidence the engine has been changed.

vibration

It's been there since I bought the car(1 year ago). Mounts were in very bad shape, I changed them right away. That's when I noticed the slight vibration, chug-chug sound. Before that, the engine rocked violently. I've got the records, no indication of an engine change, mostly serviced by MB. 168K on the car, no leaks anywhere.

Things to check

From my experience the type of vibration you are describing is caused be either 1. unbalanced compression numbers (be sure to check compression when engine is hot) 2. Injector timing / balance problems. ie. injection pump timing is set too far advanced or the injector release pressures improperly set or are not balanced. 3. Internal engine mechanical imbalance from previous work done on engine,harmonic balancer loose, flywheel/torque converter, something loose inside engine, etc.

vibs

I'll recheck all of the aforementioned items. One of particular interest is the compression imbalance. I've removed the tranny again and checked the flywheel/flex plate. I'm going to change them, although they look good. If that doesn't work, I'll go back to the engine components.

Thanks,
Bob

85CD engine vibs

Thanks For the suggestions. I redid the compression test with the following numbers on a warm to hot engine, cyl. 1-5 first compression stroke=200,200,200,160,160. After 8 stokes=300,310,320,295,300. Nothing obvious to the untrained eye. This thing starts first time every time, does not burn any oil or smoke, has good power even at highway speeds. The problem is the constant rumble and thud-thud sound at all power(above 900 RPM) settings in gear out of gear, moving or standing still.
I've done about everything in the "Diesel Performance Tuning and Repair" guide and more.

Do you have any other suggestions? As mentioned earlier, it seems to go away with the transmission removed. I've changed the xmission, fly wheel and flex plate with absolutely no change. I'm really stumped.

85 CD vibs

Kent,

Thanks for all your suggestions. I went back to take another look at the intake/exhaust area after the compression test revealed no obvious problems. After taking off the manifolds, I found what my be the problem. The intake manifold is very restricted with lots of gunk. I'm going to clean the intake manifold and get out as much as I can form the ports on the head. I think this may solve the issue. I think back to what you mentioned about the shop rag in the intake. This is very similar. The sound is like a restricked exhaust, but it looks more like a restricked intake.

Any suggestions you may have on the clean out will be appreciated. I will get back to on the results after I get everything reassembled.

Thanks again for all your help.

Bob

Cleaning intake manifold

The only good way I have found to really clean the intake manifold is to remove it and take it to a machine shop for ultrasonic cleaning. That crud is in there good and hard! You will need to remove the intake, exhaust and turbo as one unit. This will give you a chance to inspect turbo and down pipe as well. You will need a new exhaust gasket and exhaust nuts. We have these items on this website. I am not sure this will solve the problem but is worth pursuing.

1982 300D vibration

I have a vibration in P,R, & N. In Drive there is no vibration, the motor mounts look crushed, could this cause the type of vibration described.

85CD engine vibs

It is similar but not quite. New mounts.
Thanks,
Bob

85CD engine vibs

Well I cleaned out all the crud. Removed intake/exhaust mainfold. It was really grubby. I cleaned everything, inspected everything and reassembled same. At first, it seemed to have fixed the problem, but after the engine warmed, vibs returned. I'm going to continue to drive it like that for a while, I'm sure I'll be removing the head next. I'll keep you posted. Thanks for all you help.

Bob