Recently, my '83 300SD has been vibrating. At low speeds, as in normal city driving, it's more of a shake. On the highway, it vibrates pretty rapidly. I wouldn't characterize the vibrations as violent, but they are really annoying. The shaking borders on violent, because it feels like you're on a really springy bed.. keeps pushing you up and down.

The only thing that's happened around the same time this started is that I lost my gas cap, but I doubt that has anything to do with it, unless it affects the way the gas is compressed.

My suspicion is that the engine mounts need replacing, because last time I was at the mechanic's he told me that my engine mounts need replacing.

So I wanted to see if you guys agree with that, and if so, is it hard to replace them by one's self?

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Gabriel
'91 350SD 162k
'83 300SD 210k - rear-ended and scrapped
'84 300SD 210k - totalled

The passenger side motor mount is cake, the driver's side, well it isn't because of one damned bolt. No I'm not convinced that the motor mounts have anything to do with this vibration you are feeling. If you pop the hood and watch your motor at idle and it is swaying from side to side freely then you need motor mounts but it really only makes a world of difference at idle, once it is up to speed they seem to smoothen out. Are you sure it is up and down? If it were side to side I'd say check the idler arm (perhaps you should check it anyway) but for up and down the only thing it could be is some sort of a tire defect such as a shifted belt or flat spot. Normally a flat spot is only felt going slow, not at all fast, shifted or broken belts get much worse with speed and can almost always be seen as a bulge in the tire sidewall.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

Flex-disc between driveshaft and tranny? ..... thats something you can check with visual inspection.

jivadent,

Have you checked your tires for tread separation? Look for a raised portion of the tread. Jack up each wheel and look for a lump on the tread as you rotate the tire. You can also run your hand over the tread to feel for a lump. If any of the steel belt wires are showing use gloves.

P E H

The front tires were brand new 3 months ago. The back tires are old, and in need or replacement, but I can't see any lumps. I'll jack it up and see if I find any.

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Gabriel
'91 350SD 162k
'83 300SD 210k - rear-ended and scrapped
'84 300SD 210k - totalled

Replace the rear tires before looking for something more serious. I'd guess you have a belt separation in progress back there, and it will only get worse. Eventually, the tire will fly apart, usually battering the fender pretty badly in the process, and can cause you to loose control of the car.

If you still have the problem, look at the drive train -- new engine and tranny mounts, check flex disk and center bearing and carrier.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

If you have a tire separation problem, you will probably feel a sort of wobble when you drive. I experienced this in one car that had some time ago. As it got worse I felt whop, whop, whop, and then it happened, blam! The whole tread just came flying off. I had at that moment just floored the car to pass someone. Fortunately, the tread didn't hit the car I had passed.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012