99 OM606 low RPM vibration advice
 

Hi all,
I need advice/info on a weird vibration I felt while test driving a '99 E300 turbodiesel today. I have been looking for a car like this for a little while now and it has been hard to find one that really speaks to me.
I finally found one that came with no rust though it has been living on the northeast for the last 9 years so that speaks a lot about the care the car has received.
The interior is very nice and the exterior tho it needs a buff, it also is nice cosmetically speaking.
The mileage is the lowest I've seen so far for my area as well (just over 100K) and the tranny shifts nice and smooth (has not been serviced yet)
The one thing that is making me think twice is a vibration at low RPM's which coincidentally I felt on another 99 I test drove about a month back.
As you get on the gas at low rpm's the car develops a strong vibration that transfers to the body of the car, once you pass the rpm range in which the vibration occurs, it goes away completely and it is not felt at idle, in fact the motor idles very nice at around 600 or so RPM's.

My first thought was engine mounts but the owner says he had a mechanic check them and they were good. The mechanic suggested it has something to do with the idle???
I am no stranger to diesels but never owned a MB.
Car is very peppy and smooth otherwise.
I think the price is fair but I need to address this vibration or at least have a clue as far as what it could be or what to look for before I pull the trigger and end up kicking my self in the rear.

Any advise and help would be greatly appreciated.

I am very interested in this car because of actual miles, and the fact that there is no visible rust. I checked wheel wells, rockers, window frames (behind the weather strip) and found no rust at all.

plastic fuel line o-rings... very common. it's ingesting air...

Transmission mount, assuming the mech that checked the motor mounts knows his stuff. MM's are considered collapsed after they have settled down 4mm.

Have you checked exhaust components? My 98 had a vibration at 900 rpm after I replaced a section of the exhaust....turned out to be a rattling heat shield.

Our '98 has a vibration right around 1500-1600 rpm...then it disappears. Cold weather makes it more noticeable.

If the mounts have never been done, they should be tended to including trans mount as Terry notes.

The engine mounts can't really be diagnosed by looking at them, you have to measure collapse. You can also kind of tell mounts are bad by feeling a vibration in the car still, at idle in "drive" and then shifting to "reverse". If the vibration lessens, the mounts are shot.

If not, they may still be shot, you have to measure.

That's one of my thoughts as well.

I checked the exhaust as best I could from the ground but I need to do so on a lift. Can't really do that until I take possession (if I do) at which point I think that would be a somewhat easy and cheap problem to solve.
Thanks, I figure for the parts price it can't hurt and since I would be the one replacing them it shouldn't hurt the wallet as bad.
My plan is to jack the motor about a 1/4" and then test it to see if the vibration goes away as a part of the elimination process.

At this point I need to get an offer on the owner's desk and try to get the car ASAP. Just wanted to get your opinions to see if anything major has to be factored into that offer.
As usual it is hard to put a price on a used car, as there are no two alike. The thing I need to see is what major maintenance items have been done (or not) so I can weigh them in as well.
Thank you all for the quick replies;)