Whirring noise when slowing down, let off gas?

[woodman650]

Service guy at Dealership "can't hear it"... but I can and it's driving me nuts. When the car slows down, or heads downhill it makes this "cooing" sound, like a dove or pigeon. Doesn't sound normal to me. Anyone have something similar happen and able to diagnose?

[soupy]

Is it something like what ppl hear in this thread?

http://www.1addicts.com/forums/showt...light=flywheel

[woodman650]

not sure... I've got an auto transmission. But it only happens when going downhill or when I let off the gas and cruise around 30mph or slower.

[gnpower]

Originally Posted by woodman650

not sure... I've got an auto transmission. But it only happens when going downhill or when I let off the gas and cruise around 30mph or slower.

Turbo wine?

[gtaday51]

Is your 135i a vert? The turbo whine is very pronounced in the vert and it can be heard very distinctly when engine braking.

[jaybot311]

whoa i hear the same thing. Its like an owl or something hahaha. Especially when i rev up to like 3500 rpm and when the rpms are on the way down i can hear it. For some reason I noticed it after I put in the BOV. I am tempted to take the BOV out and see if the noise goes away. Its too cold out though. Anyway, I wonder if I should take it to the dealer?

[woodman650]

What's the BOV? Yeah, it does sound like an owl! And yeah it does sound like engine braking... but an owl. hmm

[jaybot311]

BOV=Blow off valve. I asked Eric at Helix and he doesn't know what it is either. Woodman, do you have any mods?

[woodman650]

none

[jaybot311]

yeah i don't know... I guess the BOV is not contributing to the sound, and I don't know why it would. Not sure man. Guess I have to take it out and bring it to the dealer. We'll see.

[jaybot311]

so i found something on the E90 post. and a guy had the same whirring noise we are experiencing. The BMW tech said its a heat shield panel that makes noise when its heated and expands. The guy on E90 will bring it in to the dealer this week and will have it fixed. My only issue is, should I take the BOVs before I bring mine in? What do you guys think? Thanks in advance.

[555]

Turbo Flutter...??

[darkphantom]

Originally Posted by 555

Turbo Flutter...??

that is too pronounced. I know what you guys are referring to and it is the turbos spooling down as you let off the throttle....

[jaybot311]

that's what I figure too. Its not a bad thing though right?

[fshowcars]

Originally Posted by darkphantom

that is too pronounced. I know what you guys are referring to and it is the turbos spooling down as you let off the throttle....

it's common... i always hear it after a burnout lol.. because you rev it up and build boost then all of a sudden aren't moving (after you let off the gas) and you can easily hear them spinning down. no biggie.

[135iUSN]

Originally Posted by 555

Turbo Flutter...??

sounds more like its saying KILL me.. I'm a Ford..

[Unknown_Car]

Hey i am sorry to bring this back 5 years later. I have same noise with my car, and i cant find nothing on e90 post. Can you guys please tell me what made this noise? what did you guys end up fixing ? Thank you in advance . I started to hear this noise after i installed my downpipes, they are no touching nothing no vibration or ratteling noise. All i hear is same noise like above when i let go the gas and it gets slower the slower the car drives .

[kioneo]

I believe I'm hearing the same noise too. Only when coasting in gear. Even a little throttle makes the noise go away. Can't be 100% certain, but it may have started after I installed my ER chargepipe. Just don't recall exactly.

Like the OP, it's like a soft cooing possibly like a dove. Not subtle if you listen for it, but easily missed if you have the radio on or aren't paying close attention.

[BMW135pls]

Originally Posted by Roma_335xi

Hey i am sorry to bring this back 5 years later. I have same noise with my car, and i cant find nothing on e90 post. Can you guys please tell me what made this noise? what did you guys end up fixing ? Thank you in advance . I started to hear this noise after i installed my downpipes, they are no touching nothing no vibration or ratteling noise. All i hear is same noise like above when i let go the gas and it gets slower the slower the car drives .

Originally Posted by kioneo

I believe I'm hearing the same noise too. Only when coasting in gear. Even a little throttle makes the noise go away. Can't be 100% certain, but it may have started after I installed my ER chargepipe. Just don't recall exactly.

Like the OP, it's like a soft cooing possibly like a dove. Not subtle if you listen for it, but easily missed if you have the radio on or aren't paying close attention.

I've read that this is the sound of the differential bearings. If you hear the sound only on decel, it tightly follows the RPM (turbo spindown will not follow RPM) and you can play it like an instrument using the throttle (on throttle = no noise, off throttle = noise) then it's the differential bearings.

[kioneo]

Originally Posted by BMW135pls

I've read that this is the sound of the differential bearings. If you hear the sound only on decel, it tightly follows the RPM (turbo spindown will not follow RPM) and you can play it like an instrument using the throttle (on throttle = no noise, off throttle = noise) then it's the differential bearings.

My sound is pretty much as you describe except the RPM part. I did some testing on the way to work today. It's much easier to hear on a quiet road (smooth asphalt) versus concrete.

Noise is most pronounced from about 50-60 mph.
Noise is there even just a 5 minutes after starting the car and driving.
Noise seems to go away when pushing clutch in or shifting to neutral.
Noise is not related to RPM, as it is present near 50 mph regardless of gear and I can't induce it at the same RPM at a lower mph.

I need to do some more checking on the turbo spindown. I've heard it before when at higher RPMs, but this just seems different to me. Not to say it isn't exactly that though. I just don't know for sure.