[dannysuen]

2011 BMW E92 335xi N55
whistling when leg off / step on gas gently below 2k rpm ( parking / driving ）, it goes away when i accelerate harder, so annoying, maybe from engine bay? I did some research and i assume it might be air intake boot leak


does anyone know how to fix it?


thanks a bunch!:


i uploaded the noise to this website, please go to the link below and click the play button on the upper-left corner
https://soundcloud.com/user-87732501.../bmw-whistling


update:
I took off cabin air filter housing and lubricated the AC fan, it's been 2 days and no noises so far, will update every week

[dannyle27]

Do you have an aftermarket intake? Your sound cloud link doesn't work. My BMS intake whistles.

[dannysuen]

if that link doesnt work plz click this one

http://vocaroo.com/i/s0tmKuxDlhii

[dannysuen]

Originally Posted by dannyle27

Do you have an aftermarket intake? Your sound cloud link doesn't work. My BMS intake whistles.

if that link doesnt work plz click this one
its stock no aftermarket parts at all
http://vocaroo.com/i/s0tmKuxDlhii

[ritzzzzzwik]

Originally Posted by dannysuen

if that link doesnt work plz click this one
its stock no aftermarket parts at all
http://vocaroo.com/i/s0tmKuxDlhii

dont think the whitsle/siren is bad atall. I have DCI and mine makes a little bit of a whistling noise below 2K RPM. But logs look great, boost is great, no leaks , nothing, and new Turbos. Dont worry about it. Do log once in a while, just to be sure (not the one you do on china throne lol).

That said, not sure what that constant squeal/squeal is?!

[Gohan335i7]

I have the exact same sound!!! Exact!! Finally someone else has it also. I guess they didn't fix it with the N55. Anyway, I would love to know what this sound is also. I Dont have any aftermarket intake either. This noise bothers the crap out of me because it does it intermittently so my mechanic never hears it... So annoying these strange noises coming from our cars. People say not to worry. Are you kidding ?! Lol Hope someone knows exactly what it is because I've been trying to get rid of this for a year. Lol!🔬🔭🔬

[dannysuen]

hey bro thank you for your reply, im wondering what did your mechanic say? did you try diy replace any part?

[dannysuen]

Originally Posted by Gohan335i7

I have the exact same sound!!! Exact!! Finally someone else has it also. I guess they didn't fix it with the N55. Anyway, I would love to know what this sound is also. I Dont have any aftermarket intake either. This noise bothers the crap out of me because it does it intermittently so my mechanic never hears it... So annoying these strange noises coming from our cars. People say not to worry. Are you kidding ?! Lol Hope someone knows exactly what it is because I've been trying to get rid of this for a year. Lol!🔬🔭🔬

hey bro thank you for your reply, im wondering what did your mechanic say? did you try diy replace any part?

[Gohan335i7]

My Indy tried a couple of things. Replaced all Belts, Pulleys,& tensioners. Also, replaced compressor. Sound still comes intermittently and I am Still trying to narrow it down. But man is the sound annoying. Just want it to go away!! Lol Another thing that might need replacing is the blower motor because it kinda sounds like it. however, he showed me that it might not be that also as it doesn't matter whether the a.c is on or not. Hopefully we find the solution soon...

[dannysuen]

update:

the noise goes off when i turn AC off, i guess i need to lubricate the fan.

[e90ca]

I think I'm having the same issue as your describing but not sure.

It's not the turbo spool noise is it? If so, that should be normal right?

[Gohan335i7]

Glad you found it. But r u sure it doesn't make the sound when it's off? Also, by fan r u talking about the blower motor?! Mine does it even when ac is off. But it is the same exact sound you have... If this fixes your problem, then I might just replace the blower motor and final stage unit , just to b safe...

[Herakles]

I hear my turbo but that's it is this what you referring to ?

[dannysuen]

Originally Posted by e90ca

I think I'm having the same issue as your describing but not sure.

It's not the turbo spool noise is it? If so, that should be normal right?

I took off cabin air filter housing and lubricated the AC fan, it's been 2 days and no noises so far, will update every week

[dannysuen]

Originally Posted by Gohan335i7

Glad you found it. But r u sure it doesn't make the sound when it's off? Also, by fan r u talking about the blower motor?! Mine does it even when ac is off. But it is the same exact sound you have... If this fixes your problem, then I might just replace the blower motor and final stage unit , just to b safe...

I'm sure the noise goes away when i turn AC off.

I took off cabin air filter housing and lubricated the AC fan, it's been 2 days and no noises so far, will update every week

[Gohan335i7]

Please do.
I will b replacing blower motor and Fsu just to b on the safe side. I hope this gets rid of it...

[JP.n54]

Mine is only doing it when I take off, after I gain speed it stops! I thought it was the PCV at first so I replaced my Valve cover, but it’s still making the sound! It used to be gentle but after sand blasting the intake port it became louder, now it’s too loud and idk what else to replace, new VC, VCG, PCV. Everything is new. The whistle sound goes away if I’ve steped on the gas all the way but I hear it very loud whistle when I’m on 1st or 2nd gear. Anything above that I don’t hear it!

[Brandoch]

Originally Posted by JP.n54

Mine is only doing it when I take off, after I gain speed it stops! I thought it was the PCV at first so I replaced my Valve cover, but it’s still making the sound! It used to be gentle but after sand blasting the intake port it became louder, now it’s too loud and idk what else to replace, new VC, VCG, PCV. Everything is new. The whistle sound goes away if I’ve steped on the gas all the way but I hear it very loud whistle when I’m on 1st or 2nd gear. Anything above that I don’t hear it!

Do a smoke test to test for boost leaks. When you cleaned the valves you probably created a boost leak.

[JP.n54]

How do I check for that?

[Brandoch]

Originally Posted by JP.n54

How do I check for that?

There are lots of threads on here about diy smoke tests. Have a search, you'll find.