I have a '95 M3 coupe with 43,009 miles.

The car is stock, and in great working order (I hope).

I have been noticing a strange metallic clinking sound as the engine is decelerating. It is easiest to hear when comming down from 3k RPM (or higher).

At a standstill, in neautral, with a hot engine and A/C off:

I rev up to 3k RPM, and let up on the gas pedal

I hear a metallic fluttering or clinking sound.

I have verified that it is NOT:
the vanos unit, the timing chains/tensioners, or anything external to the front of the engine (belts and pulleys).

On jack stands I can hear the sound near the bottom backend of the engine right near the transmission bellhousing. I cannot pinpoint whether it is comming from the lower half of the engine, or from the clutch/flywheel area.

To me, it sounds like it could be something like a little rock, or piece of something that has gotten into my transmission housing. It could also be: something rattling in my exhaust (cat), or bad engine bearing noises.

Does anyone have any insight from a similar experience? Any ideas would be greatly appreciated.

Bryan

bryguy1211@yahoo.com

Sounds like normal 3.0L noises to me. Every one I have ever seen, heard or worked on has had some amount of the "marbles in a tin can" sound as you have described. Check your oil level. If it is right at the line, add 1/2 to 1 full quart. This normally helps a lot and also eliminates the top end oil starvation issues that we experience in hard cornering

sounds like it's a loose heat shield on the cat. It happens to just about every car ever. Eventually it'll rust off completely. I wouldn't worry about it, but if it bugs you that much, crawl under there and find the offending piece of sheetmetal and rip it off. :)

could be heatsheild . could also be the guibo.

Well, I have been doing further investigation, and it does not seem to be a heat shield. I have been underneath the car with my rommmate reving the engine. The sound is not heat shield or external exhaust hardware related. It sounds like it originates in the bottom end of the engine, near the back. Specifically, the junction between the engine and the transmission bellhousing.

Also, the sound is not the typical "rocks in a can" sound which comes from the TOP of 3.0 S50 engines. I USED to have that sound, but not after I installed a new VANOS unit and timing chain tensioners.

I hope the sound is clutch (bearing maybe) related, and not inside the engine.

Any other ideas guys? Thanks!

Ahhh. How many miles are on the clutch assembly? Could be the throwout bearing

Oh yeah, I forgot to mention...

The guibo is in perfect shape, so no problems there. If the noise is transmission related, it has to be something right at the bellhousing (e.g. clutch, flywheel, pressure plate)

Anyone have good experience getting a dealer to check and replace their cats? Mine are still under warranty (barely) and I want to see if they are bad. Any suggestions? Thanks!

43,282 Miles as of today

well could be loose flywheel bolts, bad T/O bearing, pressure plate springs. Hard to say. You could get the stealer to listen to it whil on the rack

Do you get the same noise with the clutch pedal depressed, or only when you do it in neutral?

Jim

The noise happens at a standstill, or moving.

with the clutch pedal depressed or up.

and when the transmission is in gear, and the clutch pedal is depressed.

Synchros?? Maybe try switching your tranny fluid to Redline D4 ATF or MTL (depends on who you ask) I am running MTL per the crew at ERT.

If it happens with both the clutch pedal up and down, then it probably isn't a tranny thing. Especially if you hold the clutch pedal down, and wait for the input shaft in the tranny to coast down, then reproduce the sound.

Hmmm...might want to try reproducing the sound with the oil filler cap off - if it's a rear main seal, the sound should go away...

Otherwise, it could have something to do with the flywheel, the starter motor, etc...

Jim

I like the starter motor/flywheel idea....

I say that because back in March I replaced the starter. The starter was not retracting after the engine started.

Any suggestions on how to check this? I suppose I can take the starter out (PITA) and then push start the car.

Any more thoughts are greatly appreciated. Thanks!

Originally posted by bryguy1211
The noise happens at a standstill, or moving.

with the clutch pedal depressed or up.

and when the transmission is in gear, and the clutch pedal is depressed.

Sounds like a bad pilot bearing to me... This is the bearing that goes in the back of the crank, the tip of the input shaft of the tranny goes into it.

Does anyone have experience replacing a pilot bearing? Is this externally replaceable? I dont have high mileage, so I wonder why this would go bad, just a fluke?

Originally posted by bryguy1211
Does anyone have experience replacing a pilot bearing? Is this externally replaceable? I dont have high mileage, so I wonder why this would go bad, just a fluke?

The tranny has to come out, then remove the pressure plate, clutch disk and flywheel. Then you just pop the pilot bearing out with a special puller, tap a new one in, replace the rear main seal while you are there, and reassemble. I've done it on Mustangs dozens of times, the BMW should be no different...

I have a similar noise on my 95 M3 86K miles, when down-revving around 3000 RPM. I've described it in previous posts as a "mettalic hiss." If this is what your car sounds like, i'll pass on whats been said to me about my noise problem-- it's the guibo or the cats.

I've inspected my guibo (and had it looked at by a mechanic) and we agreed that it looked fine. However, I do have some drivetrain sloppiness possibly attributed to loose dif. mounts, loose driveshaft bolts, who knows? This leads me to not rule it out completely.

As for the cats, I also have a slight backfire while downshifting after already replacing my O2 sensor and spark plugs. Could be a loose part in the muffler or catalytic converter, perhaps?

I'm just living with the noise for now, since it is only really noticable outside the car.

So strange ... but I noticed this on my car as well. (Seems to be a lot of that going around these days ...) Nothing externally visible.

"Metallic hiss" describes what I've got going on fairly well. It's fairly rare, but has only come on since about last Thursday or Friday.

Since I was planning on having the clutch, fly, t/o, seals, etc. (including guibo, it's been a potential culprit for various things for a while) in about a month, I figure I'll just wait and see if I can get away with that.

Any reason to go into panic mode and get this on the rack ASAP?

I like the starter gear theory. Vibration causes the starter gear to wiggle forward on it's shaft, it touches the flywheel making a random but recurring "ting" sound... Perhaps your starter mount was machined a little out of spec causing the starters to mount up a little too close to the flywheel, maing it prone to this problem... Just speculating though.

Gary in Atlanta

Yeah, I remember someone saying that you have to be really conscientious when shimming the starter or that it will make noise. Hmmm

As soon as I have the time, I plan to take out my starter and push start the car. I will be sure to let everyone know if this fixes my noisy down reving. Keep up the great discussion....it seems like several people are all noticing the same metallic "hissing" sound.

My vote is for the guibo or heatshield. My heatshields have been welded and bent, and still make noise.

Wes
'95 M3 - 123,000 miles

I am positive that neither of those is the culprit in my case. The guibo is perfect, and I have been underneath the car with a friend reving the engine. The sounds do not come from the heatshield. I have put my hand on all of the different shields while the noise happens, and no vibration is present.