Hello everybody.
I am a new member, I live in UK, and have a 1985 300TD, RHD, 5-speed with 146000 miles on the clock. We collected it from the Sindelfingen factory in August 1985, and it has not to date let us down. It has had the ususual run of repairs and replacements, eg tyres, exhausts, batteries , fuel injectors, propshaft bearings - ie nothing that could not be analysed and sorted. Until now.
It has developed a rather hard vibration at 20mph in 2nd gear, 30mph in third gear, 40mph in 4th gear, and youv'e guessed - it 50mph in 5th gear. It only appears when the engine is under load, and disappears plus/minus 5mph either side of the 20, 30etc mph band. The vibration is principally feelable just ahead of the driver, and can be felt on the pillar in front of the driver.
All loose items were removed from the car to eliminate that source, the local MB francise replaced the engine mounts as well as the coupling at the front of th e propshaft - all to no avail.
I went to an independent MB expert, who suggests that the wrong engine mounts have been fitted. I doubt this, as the cooling fan blades sit cen trally in the radiator cowling.
I am at a loss as what to do next, and I would appreciate any advice or solutions that that other members may have found to similar problems.
The difference in mounts has to do with their hardness, and specific application, not with thickness. Height of engine has nothing to do with "is it the proper mount?"Do you just feel this vibration or do you hear it as well? Does it do it sitting still and the engine brought up to approx 2400?
Get up to the speed its vibrating at, and put the car in neutral. The rpms should drop, and if the vibration goes away, this will eliminate the engine and trans. If the vibration continues, it could be anything in the drivetrain out of balance or worn, including the u-joint, center carrier bearing, or maybe a bad tire.
If this doesn't fix it, I will happily take the car off your hands and save you any more headaches :-) A low mileage, 5-speed, RHD, wagon would be soooooo cool!!!
Jamie
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Thanks to Jamie an carnut1 for your comments.
I dont THINK that the drivetrain is out of balance, but will check further.
I ruled out tyre/wheel unbalance as the problem seems reated more to engine rather than road speed.
I can both feel and hear the vibration, it is not present with the vehicle stationary. If I can get it on to a rolling road and see what happens.
May be it is related to the mount hardness etc, but I would have thought that genuine MB parts should be ok.
Incidentally I did get the engine shock absorbers checked, they were said to be ok. I may apply some WD40 to them to see the effect.
Many thanks for your comments, again.
plantagenet.
How about the differential? It may be a shot in the dark, but a vibration at those speeds and in those consecutive gears links the engine speed to the vehicle speed. Since you've ruled out the trans and the engine, I would try the driveshaft or the differential. Don't forget the axleshafts.
Other than that, my next guess is the harmonic balancer? Just another shot in the dark. Those are some of the parts that require balancing.
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