N55 135is high-pitch noise after FMIC install

[inevitab1e]

Just got a VRSF 7" FMIC installed and notice my car is making a very high pitch electrical noise. Can be heard in the cabin and with the hood open. Sounds like it's coming from the engine bay around the alternator.

Anyone have any ideas what this noise is? Couple vids below.

[2008135i]

Does the sound change pitch or get louder as boost increases or as RPM increases? At speed, try and hold the brake and build some boost to see if its a boost leak or something else...

[inevitab1e]

Originally Posted by 2008135i

Does the sound change pitch or get louder as boost increases or as RPM increases? At speed, try and hold the brake and build some boost to see if its a boost leak or something else...

Seems to only happen when coming to slower RPM's and stopping. Then it stops after around 3k rpm. The first video is a good one showing how the high pitch changes depending on speed.

[gixracer]

check and see if your exhaust flap vacuum tube has become disconnected in the engine bay

[HomoPirate]

His car has Performance Exhaust so there's no exhaust gas flap in the system. I would check the installation again to see all the pipe connections secured. Wondering if the noise is coming from defeated/leaky FMIC.

[inevitab1e]

Originally Posted by HomoPirate

His car has Performance Exhaust so there's no exhaust gas flap in the system. I would check the installation again to see all the pipe connections secured. Wondering if the noise is coming from defeated/leaky FMIC.

I don't think it's the FMIC. This is an electrical sound that switches frequencies depending on speed. You can hear it very good in the video. I get the noise without touching the throttle.

[Sam_M]

Did you maybe disturb an earthing point during the install? Could be electrical interference as a result of that?

[Shotputted]

Definitely check your vacuum lines maybe you dislodged a connection during install. Sure sounds like my car did when I had a vacuum line disconnected on accident.

[Strmtrpr__]

I know this is an old thread but was there ever a fix. I have the exact same issue and noise

[kroymander]

I also believe I have the same issue. Here's a video:

It's a 2011 135i with ~90k miles. Stock except for charge pipe (not sure what brand) and BMW performance power kit and exhaust. Started making this noise after removing and reinstalling the charge pipe. I also replaced the 3rd brake light and installed LED side markers at the same time. The sound seems to be coming from right where the charge pipe is which is also right where the alternator is. It's a very high pitched electrical noise that does change with RPM but not proportionally like a vacuum or boost leak or a belt-related noise. It has a few pitches that it will step up and down through as the RPMs change. It doesn't change with the AC. I don't think it's coming from the rear main, PCV valve, anything like that. Could it be the alternator failing? Battery dying? I tried unplugging the LED side markers thinking maybe they were bad and it was putting a heavy load on the alternator or something like that. The car runs and drives perfectly with no issues except for the noise.

Any help would be much appreciated.

[Skotcoop]

Did the charge pipe come with a dog whistle inside? If the only thing you installed was the charge pipe remove and inspect it, really tighten the connections hard when reinstalling. God that hurts my ears to watch lol. Double check any hose connections as well, they can come off when working nearby and you may not even know it.

[kroymander]

Originally Posted by Skotcoop

Did the charge pipe come with a dog whistle inside? If the only thing you installed was the charge pipe remove and inspect it, really tighten the connections hard when reinstalling. God that hurts my ears to watch lol. Double check any hose connections as well, they can come off when working nearby and you may not even know it.

I didn't actually install the charge pipe, it was installed by the PO. all I did was pull it off to check the connections as I suspected I had a boost leak. didn't find anything obvious so I just put it back together (and swapped the lights as mentioned above), and now I have this noise that was not there before. I'll take another look this weekend to make sure I didn't miss something. I also picked up a mechanic's stethoscope hoping that will help track it down.

[dtla1]

Might be a random suggestion, but try removing the oil cap when the car is on (careful of hot oil, it won't splash but the bottom of cap and all that), and see if the noise goes away with that.

[kroymander]

mine ended up being the vacuum hose that goes underneath the airbox then around the driver's strut tower and (I think) back to the exhaust flap. came unplugged right at the strut tower and the hose fell down out of sight. finally found it just as I was about ready to take it to a shop. anyway thanks for the the help

[znaut]

Originally Posted by kroymander

mine ended up being the vacuum hose that goes underneath the airbox then around the driver's strut tower and (I think) back to the exhaust flap. came unplugged right at the strut tower and the hose fell down out of sight. finally found it just as I was about ready to take it to a shop. anyway thanks for the the help

Thank you kroymander for following up with the fix! You just saved me hours of frustration. For the next person that this happens to here is a pic of the vacuum line in question: