My 1981 300CD is a one-owner car that has been badly neglected its whole life. Consequently when it was handed down to me I changed all the fluids (ie: rearend, engine oil, radiator fluid, power steering fluid, transmission fluid) and fixed various problems with the vacuum system because the transmission wouldn't shift at the proper time. I ran 2 bottles of diesel purge through the engine per the instructions and noticed a vast improvement in engine sound and smoothness. However, for no rhyme or reason that I can find, the engine varies from idling semi-smooth initially to randomly lurching slightly while idling in drive, after you take your foot off the brake. Sometimes in park I can feel the whole car shaking and the shake and the lurch are very rhythmic in quality so it seems like maybe one or two cylinders aren't exactly firing properly. Could this be because the valves have never been adjusted? Does anybody have any experience doing this themselves, because I have heard that if the valves are adjusted and the engines are running right, they are as smooth as a Cadillac. Does anybody have any suggestions.

 

As far as the shaking goes, check your motor mounts. I just put new ones in my diezel Benz and it made all the difference in the world. If your motor mounts are bad, your car will shake like a bitch.

 

the shaking is not real bad although when i turn the car off it does sort of rattle my teeth. i will certainly check the mounts as you have suggested. do you have any experience adjusting the valves or if they really even need to be checked? i'm taking all the silence to this posting as a "yeah stupid! the manual says to do it,so do it dummy!" any suggestions? if most people leave them alone or have NEVER touched them for 150000 miles or so, that is what ill do. if they need adjusting, i will do that. i'm just looking for tips or special tools or stuff like :"adjust them on the tight side or the loose side of the measurements". thanks for the reply squablow.

 

211 hits and no one can give some feedback? as a side bar the car is running better after a few tanks of fuel with mmo and diesel kleen. but has anyone any info on valve adjustment?

 

Had mine done at 150,000 miles, sounds the same, idles the same, same power. Not a difficult job at all. I agree with the engine mounts being checked. Merecedes makes a template that the technician puts next to the mount to verify if they are collapsed enough to replace. Most people forget about the little shock absorbers on either side of the engine that cancel out vibration as well. I would think that by removing the lower bolt on the shock and pushing it up, you could determine if they are weak. Smooth as a Cadillac diesel? Just kidding!

 

thanks carnut. i have checked the mounts and they LOOK fine. the shock absorbers were recently replaced and have not leaked so. as i said in the post the slight surg at idle has been a non issue for a while. the manual says to adjust the lash every 30,000 or so, so i am going to check it anyway. the feedback i get from most is that it is relatively easy to do and since i KNOW it was never done to this car, i may as well do it. i think the biggest improvements have already been seen with the diesel purge and a few tanks of cleaner and fresh fuel. the car really runs well,ALMOST as smooth as a caddy. but much nicer looking! thanks again!