sd engine vibrates at 3000 rpms - PeachParts Mercedes-Benz Forum

jimdbrr · #1 06-26-2006, 07:54 PM

Hi i've been reading awhile and decided to join up. My 82 300sd, 300k runs, great, uses almost no oil , has no blowby, gets 28mi gln, and still looks new. But......at 3000rpm standing still or on the road the engine makes more noise and vibrates more than it seems like it should. Any ideas

PatricdeBoer · #2 06-29-2006, 04:48 AM

I'm going to bump this because this is my dad and I drove the car tonight. The problem is that there is kinda grating vibration that happens within a very narrow rpm range, right about 3,000. Like he said it happens when the car is driving or sitting still. It is almost like a metal to metal sound. I haven't had a chance to get under and poke about, but does anyone have any advise on how to locate the source of the vibration? Maybe I'll get lucky and it'll be the wrench that I dropped down the side of the engine and forgot about.

vstech · #3 06-29-2006, 09:02 AM

take a short length of hose held to your ear, then poke and prod around on the car while it is vibrating. should tell you closer where the noise is coming from.
from that description, it could be anything from loose bolts to damaged valve followers, etc.
narrow it down, and post back with closer details, I bet we find it. better yet, post a sound clip and we can listen to it.
John

barry123400 · #4 06-29-2006, 09:37 AM

How about broken air cleaner mounts resonating at about 3 k. Quick and easy to check but does not exactly match your description. On the otherhand they are famous for letting go.

SD Blue · #5 06-29-2006, 10:37 AM

Does it occur with no load? (parked and revved to 3K) or with load? (highway) or both?

If it is only highway, the source may be drivetrain related.

PatricdeBoer · #6 06-29-2006, 01:01 PM

It happens without a load, just sitting in the driveway, so I'm positive its not the drivetrain.

Mistress · #7 06-29-2006, 01:16 PM

motor mounts?

rrgrassi · #8 06-29-2006, 01:20 PM

Check transmission fluid as well. The torque converter, tranny oil pump, and input shaft spins with the engine while running or turning over to start. Also, check to make sure the starter bendix is retracting after the engine starts.

Maroon 300D · #9 06-29-2006, 01:20 PM

Quote:

Originally Posted by Siduri19

motor mounts?

I was thinking that, too. I know if they go the vibration can become such that oil cooler lines can be hit...

By any chance, though, does this happen more when it's hot? Or is it not related to the ambient temp.?

I ask because on hot days I often have more vibration. In my case I think maybe I need a new rack dampener pin. I have the old silver one and I wonder if the spring compresses too much in the hot weather.

Diesel Giant · #10 06-30-2006, 09:11 PM

Could be the pin. Is the idle speed set properly?

SD Blue · #11 07-03-2006, 10:54 AM

One of the areas that I found is similar to your description is the proximity of the air cleaner to the bracket for the EGR control valves on top of the valve cover. I split a section of vacuum hose and glued it, with automotive GOOP, to the edge of the bracket and has helped significantly.

PatricdeBoer · #12 08-16-2006, 12:28 PM

We have solved the elusive vibration! I was under my dads car (Jimdbrr), looking for points of contact when I noticed something wasn't quite right, like maybe the transmission was only being held onto the engine by the starter bolts!

So, appartently when his mechanic put the engine back in the car, he forgot, or just hand tightened most of the bolts. Needless to say, the with the addition of several bolts, the vibration is gone. Had I not seen the bolt holes, I never would have thought of that.

SD Blue · #13 08-16-2006, 10:32 PM

Finds like that make me wonder what other bolts may be missing.

Good eyes!