I'm stumped. I was driving along the interstate last night, everything was smooth and quiet.

All of a sudden, from somewhere under the car, there was a sound like a stick got jammed in there somewhere and it was rubbing against the wheel or maybe a flex disk. Kind of like an amplified version of sticking a playing card in the spokes of a bicycle.

The sound is following the speed of the drive train and doesn't seem to be related to the engine speed. Once I slowed below 20 MPH, it went away. Also, it didn't seem to change regardless of whether I was coasting or accelerating.

I checked everything out and there's nothing rubbing or touching anywhere underneath. Also, the flex disks look fine. The only thing I found slightly strange is that when idling and having an assistant switch between drive and reverse, looking at the rear axles, the differential side of the CV joint moves slightly independently of the axle.

That is to say, I could detect a slight twist in the CV joints which was visible as a small movement on the large end while the axle end remained fixed. Don't know it this is significant.

Finally, I can't determine exactly where the noise is coming from. The car has so much padding that it's hard to get an exact direction. The next step will be to run the car with the wheels off the ground to see if I can duplicate the noise.

Any ideas?

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

fender guard ?

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1999 W210 E300 Turbodiesel

Fan shroud? Tall parking stops sometimes catch the lower rad and push it back toward the fan.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

It seems to be totally unrelated to the engine. I can put the car in neutral while driving and rev the engine and the sound remains the same.

Update:

I put the car up on stands and ran through the gears. Anything above around 25 mph and the drivetrain starts shaking and I'm hearing the sound like the drive shaft is bouncing off of the exhaust heat shield. So, this sounds like the front flex disk in combination with a collapsed rear mount.

Does this sound like a reasonable hypothesis?

I have to wait until I get the car up on better supports before I go laying under it while it's running/rolling for a more definitive diagnosis.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Sounds reasonable. There should be some visible stress cracks if not chunks of rubber from the flex disk.

About a year ago I found urethane flex disks that claimed to be much more durable. The closest I can find now are these https://www.revshift.com/shop/drivetrain/bmw-flex-disc-small-lk-78mm/12mm-.php

I will keep looking.

found a picture of it, still looking

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

I would definitely like to learn more about the urethane flex discs available for the W210 diesels if you can find it.

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Ed
-1984 Mercedes 190D 2.2 5-speed gray market(bought@30,000 miles) (Sold back to original owner@170,000 miles)
-1999 Mercedes E300DT (245,000 miles)
-1999 Mercedes S500 Grand Edition (80,000 miles)

That could easily be the carrier bearing or the shaft binding on the spline, too (causing the shaft to orbit slightly). It doesn't sound as though you're still driving it, but if you are, stop doing so until you get it fixed.

Good luck.

The 190rev guys have been working on it, I know there is another source

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

Check the fan shroud and fan aglinment, my fan was leaning hitting the shroud. The engine mounts failed to the point that the fan leaned forward hitting the shroud.

__________________
Gary
Experience is something you get, Just after you needed it....
'99 E300 295K, '83 300D 220K, '75 240D 185K sold
'80 MCI Bus Conv DD 6V92TA, w/4 cyl. Kubota diesel GenSet 12.5KW

OK, I figured it out tonight. The center carrier boot had torn and a flap of rubber was flailing the heat shield. It took a certain amount of speed to get it to spin out that's why it would only do it above 20 MPH.

In the "while you're in there" department, I think I'm going to get a new carrier bearing as well. Any ideas for other things?

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

The trans mount is close by and easy to do if you haven't done it already.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

That sounds good. I have replaced the main mounts but not the transmission mount. I need a few more dollars to get free shipping on my order!

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250