Whistling sound upon acceleration

dreamspeed wrote

Nope, going on a year with this nuisance.

Next logical step is to remove the idle control unit and clean it throughly but it's more of a pain to remove than I thought and I haven't gotten around to it

you're on the job!

This weekend?

We're counting on you!

Any luck finding the issue?

Munichm3 wrote

Bro, it's obviously from your turbo

Speak for yourself...not everyone has updated to the m4...

BOOF-M3 wrote

Any luck finding the issue?

I might have a new lead on potential root cause. I'm going to check it out this weekend

I have nothing to contribute to this thread except - that's a sweet gpower setup

BOOF-M3
Talk2meg00se

Fingers crossed but I think fixed the problem!

Credit goes to TudiM3 for finding the root cause... Google "HELP NEEDED whistle noise from Intake" and you should find that thread

The whistling sound comes from a loose piece of rubber in the plenum. If you take off the plenum and look into the hole where you connect the idle air tube (pic 1 circled in red) you will see a piece of rubber sticking out.

It looks like over time the rubber starts sagging and creates an air gap in that area. (pic 2 circled in red). When air is sucked through there it makes a whistling sound. If you disconnect the tube the whistling goes away because there is not enough air flowing through that area to create the sound.

The way i fixed it is to use a toothpick to apply some RTV into the gap to seal it. pics 4 and 5. You can also true to glue the rubber piece back into place with epoxy but that will be more difficult due to the extremely limited space you have to work with.

It's a very simple job, all you gotta do is take off the plenum and apply RTV. I've taken off the plenum so many times now I can do it like 5 minutes. The key is to use a flexible driver with a 6mm socket.

*Top Tip: Tape the 6mm socket onto the extension so it does not fall off! Otherwise you'll end up wasting like 30minutes of your life trying to find the socket that fill into your engine bay.

Good luck!

*Note: The reason why i have all that crud in the attachment hole is because I originally thought the whistling sound came from the hose not sealing tightly enough against the hole so i used some liquid gasket to seal it better.

Is it fair to say that this is the only opening on the plenum that could have a loose piece of rubber? Does every opening have rubber? It's making this whistling noise on both my 2011 M3's so it probably makes sense that it is the identical issue in the plenum. Just trying to find out if there are lots of loose area. Good work and thanks for solving the issue.

BOOF-M3 wrote

Is it fair to say that this is the only opening on the plenum that could have a loose piece of rubber? Does every opening have rubber? It's making this whistling noise on both my 2011 M3's so it probably makes sense that it is the identical issue in the plenum. Just trying to find out of there are lots of loose area. Good work and thanks for solving the issue.

Tbh i have no idea if there are other pieces of rubber, but if you want to do some testing before taking the plenum off just disconnect the tube and see if the whistling goes away. If it doesn't then most likely the cause is something else, if it does then most likely it's the same issue.

There's a bunch of other reasons for a whistling noise such as worn pulley, power steering fluid low, vacumn leak, loose connection somewhere in your air intake circuit etc.

My case is one of those outliers where the common diagnosis didn't pan out and the root cause is some obscure issue.

iirc there are no rubber gaskets around the 8 openings for the throttle bodies that i could see

dreamspeed wrote

Tbh i have no idea if there are other pieces of rubber, but if you want to do some testing before taking the plenum off just disconnect the tube and see if the whistling goes away. If it doesn't then most likely the cause is something else, if it does then most likely it's the same issue.

There's a bunch of other reasons for a whistling noise such as worn pulley, power steering fluid low, vacumn leak, loose connection somewhere in your air intake circuit etc.

My case is one of those outliers where the common diagnosis didn't pan out and the root cause is some obscure issue.

How do you disconnect the tube?

The tube is located where I drew the red circle in the back.

The connector on the tube is the same as the connector of the tube I circled in the front.

You need to remove your air box and then you can reach back there to disconnect it.

You squeeze the connector together to release it but depending on the size of your hands and dexterity it could be super easy or a pain in the ass to get loose

Still whistle free?

nick3753 wrote

Still whistle free?

Yes

Thank you soooooo much for posting this info. I have been struggling with this exact issue on my 2013 M3 for two years now. It has been to the delearship several times and they have even called in their regional tech / mechanic to check it out. They isolated it down to the same ICV tube that you found and swapped out the ICV. After that, the dealership’s service manager pretty much told me that I had to live with it and refused to work on it further. I guess I was keeping his guys from oil changes and brake jobs that make him money. Most of those guys are “part swappers” and get in trouble for spending time with these cars to do real troubleshooting. What you’ve done is fantastic. Really great troubleshooting by you and tudim3. I read his posts a few weeks ago but your troubleshooting steps made it all make sense. Thank you for not getting discouraged by all the “you need to change your belt” suggestions when demonstrating how you can change the pitch/severity with the amount of throttle opening at different rpm ranges. I dealt with several mechanics that made those suggestions even though I could demonstrate the whistle getting louder as soon as I took out the air filter, and then again louder when we took off the air intake “snorkel”. I can pretty much make my intake play a tune while I’m driving down a quiet road. It drives me bananas!!! I have friends with M3’s and their cars have this exact problem too. I’m anxious to take my plenum off tomorrow and fix it. Seriously, I can’t tell you enough how happy this has made me. Great work!!!

Splat789

Glad to be able to help. I completely understand your frustration. I had the whistling noise for a long and at one point I even did a "ghetto fix" by disconnecting the tube, capping off the hole from the plenum, and sticking an air breather filter onto the tube. The whistling went away but it caused an intermittent IAT sensor fault which i thought was unrelated and spent months trying to figure out the cause!

I've owned the M3 for ~5 years and have continuously had misc. issues.

I've finally figured out and fixed all except one.... a buzzing sound at 3k RPM...sounds like it's from a heat shield lol

X

dreamspeed wrote

BOOF-M3
Talk2meg00se

It's a very simple job, all you gotta do is take off the plenum

Ok, easier said than done. Got this far and realized that the plenum removal is not intuitive or easy at all.

Anyone aware of a helpful step-by-step for this?

dreamspeed wrote

The tube is located where I drew the red circle in the back.

The connector on the tube is the same as the connector of the tube I circled in the front.

You need to remove your air box and then you can reach back there to disconnect it.

You squeeze the connector together to release it but depending on the size of your hands and dexterity it could be super easy or a pain in the ass to get loose

Why does it make a difference whether you disconnect the tube in the front or the back? The front is a lot easier to reach.

Talk2meg00se wrote

dreamspeed wrote

The tube is located where I drew the red circle in the back.

The connector on the tube is the same as the connector of the tube I circled in the front.

You need to remove your air box and then you can reach back there to disconnect it.

You squeeze the connector together to release it but depending on the size of your hands and dexterity it could be super easy or a pain in the ass to get loose

Why does it make a difference whether you disconnect the tube in the front or the back? The front is a lot easier to reach.

The tube in the front does something completely different than the one in the back.

If you are having the same issue I had then removing the front tube doesn't do anything.

Search for the throttle actuator diy. I believe that has instructions on how to remove the plenum

This was the exact cause of my whistling. Thanks for the help!

Excellent thread Dreamspeed, finally got a look at what was going on at the plenum and realized that the plenum was not seated in slot 4 at the rear of passenger side. Made sure it was seated, tightened up the clamp and the whistling is gone.

After reading this post, I just diagnosed my intake whistle as well. I've been chasing that sound for a while. It was as described and so I removing the hose at the back of the plenum and made it go away. Looks like the plenum is coming off for some RTV action. Thanks for the awesome diagnosis!