Have you ever changed your motor mounts? I'm guessing here but I developed a slight buzzing sound when I would back out of the garage and it had a metallic buzzing sound up under the dash for a second or two as the motor hit a certain low rpm. The rubber sags over time then metal hits metal on those mounts. I changed mine and the sound was gone. Mine is an 08 with probably 70k on it at the time.

 

Have you ever changed your motor mounts?

I don't believe the motor mounts were ever replaced, but I would definitely not describe this sound as buzzing. I do get some buzzing in other situations, almost as if the hood was resonating, so it's probably time to get them replaced at some point soon anyway.

Thanks for the suggestion.

 

Hey, i have a 2016 F10 M5 and i too am having a similar sound and it is so frustrating. i will try to record it on video tomorrow and post it up. if anyone has any ideas that would be a great help. mine sounds like its coming from the left side down pipe.
let me know what anyone thinks thanks

 

Was able to capture a better video tonight; turns out it's easier to hear it with the windows up.

Headphones still very helpful, but again, it starts around the 12-second mark and lasts for about 4 seconds. It then stops on its own, even if I just sit there idling in neutral/first.

The start of the sound does seem to coincide with when I feel the SMG release the gear into neutral, but that may be me trying to connect two disparate events.

 

CSB?

 

Or throw out bearing. Sounds like it continues after V=0 so wheel bearings and other vehicle speed things would be eliminated. I'd go around the engine bay with a mechanic's stethoscope and touch anything with a bearing. A failed bearing does not always make audible noise. Not sure but assume the cooling fan can be activated in ISTA/INPA.
You can also try driving with someone sticking their head out the pass window, looking perpendicular to the car, then repeat out the driver rear in order to isolate front to rear and perhaps side to side.
Andy

 

Or throw out bearing. Sounds like it continues after V=0 so wheel bearings and other vehicle speed things would be eliminated...

Thanks for the reply; yeah, that was my initial guess/fear as well. Trying to convince myself that it "cannot" be since everything but the transmission itself was rebuilt (hydraulics) or replaced with brand new parts (sachs clutch kit, LUK fw, etc) about 3yrs/20k ago... Neither I nor p.o. drive like maniacs, usually.

Any tests I can run in ISTA on those clutch parts? Or mysterious values that I can look at? I successfully did a whole re-learning procedure just a few months ago. This "seems" more of a mechanical thing than a software thing however.

CSB?

As far as driveshaft bearings, since the sound continues once the car is fully stopped, I would think that's a less likely culprit, though those things always manifest themselves in weird ways. (Had a CSB go bad on my e61 recently that then only vibrated at exactly 20mph.)

As far as other bearings or spinning parts, I guess there aren't too many things that spin down as the car comes to a stop, but do continue to spin for a couple seconds after it has come to a complete stop. Maybe I can locate it by poking around with a stethoscope, but it doesn't seem to make any apparent noises when just standing still (after the initial couple seconds anyway), so I'm not sure if I would expect to hear it even with a stethoscope.

It's definitely front, louder right than left, but not by much.

 

I agree it's likely more mechanical since no codes. I was just thinking component bearing since they tend to get noisy before failure, and can have small ranges of excitation to get that audible tone. With a mechanic's stethoscope directly on the housing I'd think you'd hear crunch etc and not hear it with the naked ear.

Andy

 

sounds like a wheel bearing

 

Thanks for the suggestion. I had always thought a wheel bearing was more of a droning noise, and one that's RPM-dependent. This one continues seconds after things have stopped moving and I certainly don't hear it while driving in general.

Drove the car today; usual route, no noise! So that's weird.

I'm set to change the oil next weekend anyway, so will get it up in the air and start poking around. Hopefully will be able to hear something at idle from either the transmission or the engine bay.

 

Well, did the oil change (overfilled for the first time ever thanks to stupid electronic dipstick: said -0.5L on initial fill, added 1.5L, then readout said 1.5L! wtf. drained the cap, now it says 0.9L. /shrug), but didn't get anywhere closer to diagnosing my rattle.

Spent some time listening, poking around, but nothing sounding out of the ordinary to me -- ordinary of course being a cacophony of noise, an "agricultural machine" as M539 likes to say.

There is some possible excess noise from the back of the engine, and if I touch the pass.side exhaust heatshield/cover below, there's a fair bit of clanking and rattling. Not sure if that's normal. Everything else sounds fine to me, including the bellhousing -- though this is with just the car sitting in neutral and I only hear the noise in question after driving.

fwiw, here's what a cold start sounds like; you can maybe hear what I would call the excess noise (a rhythmic clattering from the back of the bay that ebbs and goes, beyond the injectors ticking and all the VANOS things).

 

Well, here's a potentially interesting new symptom:

I shut off the engine mid-rattle this morning, and when I started it back up a couple hours later, it resumed exactly from mid-rattle, continuing to rattle/flutter for a couple seconds before the noise went away (and not to return since I only drove it for it about 10 minutes).

Would that suggest something like a flywheel? Strange...

 

I wouldn't think flywheel, with the thinking that if it were failed in some way (crack, broken spring or rivet) it would be there all the time and likely felt/heard with a mechanic's stethoscope.
It sounds like a resonance of sorts, and having it happen only at low engine speed with no/low load leads me down that path. Have you put the trans in neutral from, say 30, and coasted down from there? What about bumping up the engine rpm in the same situation you were able to record the video. Again thinking throw out bearing - what if you depress the clutch (I assume this is possible via ISTA)?
Andy