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1999 S420; 2007 S600
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416 Posts
Discussion Starter #1
Hi folks,

This is more of a general mechanical question vs. W140-specific, but on our S420, we've got a pronounced bad-bearing sound, but only on left turns at speed. It's coming out of the front end but I can't readily identify whether it's one of the wheels or some bottom-end problem in the engine.

Any suggestions as to what bearing it might be? I would think bad wheel bearings should make the bad-bearing sound going any direction, particularly at low speeds, and this does not - only at, say, 20+ mph, on hard left turns. However, that should be true of ANY failing bearing. That makes me wonder if it's something else - power steering pump, etc.?

Thanks for your thoughts!

-Andy
 

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95 s420 - 99 740IL
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19 Posts
I have the same issue except on mine I think the sound is coming from the back of the vehicle. At first I also thought it might be the bearing but it did not make any sense for the sound to appear only on left turns. It was even more pronounced if I stepped on the throttle while turning so I figured it must be something around the drive shaft. I think it is the drive shaft bearing because there is a little play there. It also might be the guibo, but from appearance it does not seem to be damaged. I still haven't tackled this issue but it's high on the list.
Cheers.
 

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'84 300DT, '97 S320
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682 Posts
I had a bad front left bearing on a 1974 Plymouth Duster - it's been awhile (~1975), but I seem to remember it made noise mostly during left turns and at some speed also -- not so much when making a left turn. I specifically remember the noise on a particular left curve. It didn't get a whole lot worse, because my dad changed it after I brought it to his attention.

Even without much car experience at that time, I also thought it odd that it did not make noise all the time.
 

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1999 S420; 2007 S600
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416 Posts
Discussion Starter #5
Sure enough, that's my problem - it's that insulation material that is falling down and rubbing.

However, on my car, it's not rubbing on the shaft, it's rubbing right on the output plate from the transmission. There are no screws anywhere near that, that I could use to suspend that insulation back up against the frame.

It seems like something that is almost guaranteed to happen sooner or later. Have most W140 owners experienced that?

I think that's only sound-deadening insulation, not heat... so it might be OK to just remove it. However, I'd prefer to find a way to push it back up against the frame of the car... I don't know how much noise it really dampens out from the driveshaft.

I don't even want to know how much a replacement from the dealership would cost. Somewhere between $1000 and $Infinity, I'm sure.
 

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1999 Mercedes Benz S420 45K miles, 2007 Acura MDX, 1997 Honda Del Sol
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84 Posts
It could cost a lot of money to fix that at the dealership. So many parts must be removed to have a full access and workaround. In my case it came back after two weeks. I was able to get read of it by pushing the insulation up. But I guess it sagged back. Keep us posted on your progress of fixing it.
 

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1999 Black S320.. 278,000 and still pulling strong
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183 Posts
try some zipties or something like that bro... zipties with some kind of shim or somthing like that
 

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1999 S420; 2007 S600
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416 Posts
Discussion Starter #8
Zip ties & shims eh? Not too sure about that. There's nothing up front there to tie it TO.

I may need to take extreme measures, such as drilling the frame, putting in some kind of rust-proofing compound and a rubber grommet, with a push-fastener. Basically fabricate the kind of support for the thing that they should have put in there to begin with.

I do see the screws you used to hold yours up, and that makes sense if that's where it was sagging. The stuff you used is called duct hanger straps. I bought a roll of it at Home Depot in the duct-work section. That part of the insulation fitting IS sagging on mine as well, but it's not close to the driveshaft yet. And, whatever I do to press the insulation back up against the frame over the rear end of the transmission, should hold up the part further back by the shaft.
 
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