This can't be good...Metal Sound

[J. Huber]

So, I have recently discovered a "new sound" that has me worried. It occurs only when the car is in gear and exactly at the point the RPMs hits 1250. Once the revs go beyond or drop below, the sound disappears. It is coming from somewhere underneath about the center of the car. It is a metal-ish sound -- a little like a faint crumply grind -- that I can hear only because the top is off. Its not loud but I hear it. The car is running great as usual otherwise. Any ideas?

[hill]

So, I have recently discovered a "new sound" that has me worried. It occurs only when the car is in gear and exactly at the point the RPMs hits 1250. Once the revs go beyond or drop below, the sound disappears. It is coming from somewhere underneath about the center of the car. It is a metal-ish sound -- a little like a faint crumply grind -- that I can hear only because the top is off. Its not loud but I hear it. The car is running great as usual otherwise. Any ideas?

Flex disc?

Oh and James I need your expertice food and liquor provided.

[J. Huber]

Well, D I am afraid food and liquor are my expertise.... (send me an off-liner)

[mdsalemi]

WARNING:   Better get the car on a lift and do a thorough inspection.  You do NOT want to know the possibilities of either a flex-disk failing, or anything in the driveline.  TRUST me on this, been there and done that..

...as I drove onto a highway, with similar noises, and suddenly the whole shooting match let loose, with parts and metal and trans fluid spewing out from underneath my Pagoda, my wife (behind me in the daily driver) dodging this mess says to herself--

THIS CAN'T BE GOOD...

Really, you have a problem.  Find it and fix it.

[J. Huber]

Hey Mike. Thank you. Believe me your warnings are well-taken and I am sufficiently worried.

I have read about both yours and others having a sudden flex disc failure. Not a good thing. So. Here we go.

Fact is, my trusted mechanic has retired since my last visit and sold his shop. The new owners may or may not be able to handle my 113. Not many can in these here boondocks. So I am a little in a pickle.

If I (as in me) or a mechanic can get to where they can "inspect" the disk, what are we looking/listening for? The tech manual is pretty clear on how the flex disc is replaced so that is a start. I will look for the obvious -- rubber deterioration and any visible oddities. But will the driveshaft need to be spinning to inspect it correctly?

Finally -- always the optimist -- in the Tech manual depiction of FD replacement, there is a small grease nipple reference. Am I wise to get some grease in there? It has been years and years I am sure.

Thanks Guys.

[mdsalemi]

Jim,

I think any competent mechanic, who is interested in solving the problem, will help you.  You need to get the car on a lift and do a proper inspection.

I don't know precisely where you live in CA but you should be able to find someone to help.  Call your local MBCA, BMWCCA, Porsche Clubs and find out where they get the cars serviced.  I'm sure there are independents around to help.  Call Dave Gallon on this site; Brian Peters in San Diego.  You may have to go into the Stockton area or Reno area, I'm not sure.

Specifically look for loose or missing nuts and bolts.  Check for play in any and all "couplings".  Look for any "shiny" metal meaning something rubbing.

Good luck.

[J. Huber]

Well Mike, considering the MB section I am in and the nearest dealership are both about 60 miles away, you gotta know I am in the woods. Oh we have a whole bunch of car shops -- but not many that do MBZ...

There are a few independents that may work within a larger radius (say 50 miles) -- I was just spoiled to have someone only 5 mins away for the last 10 years. Dick M. uses someone also sufficiently close (15 miles away) so I will try him first. He did my subframe mounts, engine mounts and shocks adequately so he knows the car a bit.

I may crawl under myself just to have a look. Then its "Honey, guess what?" time... 

Any others have thoughts? Thx.

[waqas]

Hey James,

Crawl under there with a camera. We'll try our best to help over the web!

Then, apply grease to the driveshaft nipple and take it for a test-drive.

[Peter van Es]

If your flex disk is really shot so that it makes funny noises in your drive train, you'll see frayed bits hanging of off it - actually quite easy to spot. Frayed bits is not good. Missing bolts is not good either.

If not, it could be something else.

Indeed take some photographs... but also remember Cees' adventures with a funny noise (bearings, brakes, he investigated everything and then some, but I forgot what the cause was eventually).

Peter

[Dave Gallon]

Also take a look at the center support where the front and rear halves of the drive shaft join together. In addition to the flex disk, noises of this general type could be caused by a bad universal joint, bad center support bearing, or bad rubber sleeve at the center support. So, take a look at the flex disk and look for obvious failures (minor problems with the flex disk should not cause noises) and inspect the rubber sleeve at the center support. If you do not see anything in those areas, you may need to partially or completely remove the drive shaft to check the bearing and universal joint.

[J. Huber]

So, I jacked up the car and crawled under for a cursory look (until I actually take it to someone who knows what they are doing...)

First of all, I really was not sure where I was supposed to look. There is a small cut out in the floor where I can see the drive shaft and a joint with rubber parts. Thought that was the flex disc but it doesn't resemble the tech manual pic so I think that wasn't it. Right? Then closer to the transmission I think I see some of the disc. But does that bolted-on cover plate have to come off for inspection? From what I could see through the small openings, things look tight and pretty good. But no way could I see the entire connection let alone get to a grease nipple.

What I did see is a much more apparent transmission fluid leak than before. I have always had a bit of fluid forming but it rarely hits the ground. This time, a good bit was forming on most of the pan bolts and around the casing -- and some on the floor.

[J. Huber]

FAST-FORWARD to May 23 from October...

Well, I have continued to live with the mystery sound. A grinding when the revs hit a certain point. Only in when in gear and under speed... For months I have heard it, cringed, and kept driving. I still have no mechanic but in addition to my own visual inspection of the flex disc back in October, I have added rear end fluid (it was low) but still no change.

Then yesterday, I put the hardtop on for a car show (that's another thread!) and I heard it louder than ever. Possibly due to the acoustics? Anyway, I decided to pump a little grease the driveshaft -- took it for a spin... No change, still grinding... It has to be inside the transmission, I thought. And that CAN'T be good... I was resigned to disaster. THEN it happened.

Kind of frustrated, I put on the handbrake, hung out the door, and revved it to the grind spot. I wanted to verify it was coming from transmission tunnel. And holy cow, my ears and eye were drawn to the nut on the center muffler mount. It was shaking and shimmying like crazy. I was so pumped! Raced into garage, crawled under with a 13mm wrench and baam. Took a spin -- nothing but the usual purr!!  Huge relief!!! I had to share it. thx.

[mdsalemi]

Jim, this reminds me of this creaking-groaning sound I would have whenever I would bring my car to a stop.  Several people looked at the car, nobody could determine the problem.

Then one day, when I had it at my local shop for an oil change, the mechanic and I went for a ride* and I demonstrated the sound.  We got the car on the lift and he took his wrenches and TIGHTENED or tried to check just about everything he saw.  Problem turned out to be the large nuts that hold the bushings/clamps on the sway bar in place.  Though all looked fine, it was not torqued down properly.  Tightened them all up and the problem went away.

Loose screws, nuts and bolts will be your car's undoing if you don't keep them in line.

*far too often nobody wants to take a ride to hear a sound or anything.  Force them if necessary at wrenchpoint.  

[Eminent]

I had a similair sound that has more or less to do with the exhaust.
See here.
It's indeed a huge relief when finally it's gone.