Loud whine after shutting off car

transcendid · 07-19-2021, 09:17 PM

Hey all… after driving and shutting my car off today, I heard an awful noise that sounded like feedback when you get a mic too close to the speakers. Thinking it had something to do with my phone and stereo system, I disconnected those from idrive, then tried to recreate it. So I started it back up, revved a few times, and shut it off. It did the same thing for 3 on/off cycles, then did not do it on the 4th. Noise seems to be coming from the drivers side of the engine bay.

Video Link below… any ideas??

https://drive.google.com/file/d/1c5x...w?usp=drivesdk

premier3is · 07-25-2021, 11:09 AM

Quote:

Originally Posted by transcendid

Hey all… after driving and shutting my car off today, I heard an awful noise that sounded like feedback when you get a mic too close to the speakers. Thinking it had something to do with my phone and stereo system, I disconnected those from idrive, then tried to recreate it. So I started it back up, revved a few times, and shut it off. It did the same thing for 3 on/off cycles, then did not do it on the 4th. Noise seems to be coming from the drivers side of the engine bay.

Video Link below… any ideas??

https://drive.google.com/file/d/1c5x...w?usp=drivesdk

It sounds like a harmonica under your hood lol. All jokes aside wish I could help but I think you should take this into your dealership to get it checked out. Never seen anyone report something like this here before so keep us updated.

transcendid · 07-25-2021, 01:38 PM

Emailed video to service manager and foreman, who thought it could be related to the AC system, specifically the compressor or the expansion valve. The noise is definitely not always there on shut down, and of course was not present when dealer drove it. They ran a scan for any fault codes with AC system, and finding none, returned the car and asked me to pay attention to how to reliably reproduce it.

So far, what it seems like to me is if I idle the car for a while (10+min) or drive somewhat spiritedly with the AC on a low temp (working hard), the noise will be present about 30 seconds after I shut off the car. Sometimes it's been loud and goes on for 30 seconds or so, other times it kind of fades in and out at a much lower volume. And if I start the car again while the noise is happening, it stops.

It kind of sounds like some kind of metallic resonance noise, almost like a tuning fork.

So far, AC seems to be working fine. Really hoping it does not quit on me at an in opportune time before I have a chance to figure out what's wrong. Will definitely report back!

transcendid · 07-25-2021, 06:02 PM

Ok… pretty sure it's this pipe. After driving with AC on it, it is cold, has condensation on it, and I can feel it vibrating in tune with the noise. Does this help anyone narrow it down?

transcendid · 07-26-2021, 10:26 PM

Quick update - dealer sent my videos to BMWNA who said they suspect the expansion valve is to blame and recommended replacement. Will try that and report back!

transcendid · 08-07-2021, 01:59 PM

Expansion valve replaced. Knock on wood, have not heard the noise since.

Montbason · 08-22-2023, 02:58 PM

Quote:

Originally Posted by transcendid

Expansion valve replaced. Knock on wood, have not heard the noise since.

thanks for the post, I spent month trying to find a solution i have exactly the same problem 320i G20 and The dealer had no clue. now that I see your post, hopefully by replacing the expansion valve will solve the situation. ill post next week if this worked.

Montbason · 09-02-2023, 02:17 PM

Problem solved. Just changed the expansion valve under warranty and no more noise.

07-19-2021, 09:17 PM	#1
transcendid Private First Class 45 Rep 125 Posts Drives: 2020 m340i RWD Join Date: Mar 2016 Location: Maryland iTrader: (0) Garage List 2020 BMW M340i [0.00]	Hey all… after driving and shutting my car off today, I heard an awful noise that sounded like feedback when you get a mic too close to the speakers. Thinking it had something to do with my phone and stereo system, I disconnected those from idrive, then tried to recreate it. So I started it back up, revved a few times, and shut it off. It did the same thing for 3 on/off cycles, then did not do it on the 4th. Noise seems to be coming from the drivers side of the engine bay. Video Link below… any ideas?? https://drive.google.com/file/d/1c5x...w?usp=drivesdk
	Appreciate 0 Tweet Quote

07-25-2021, 01:38 PM	#3
transcendid Private First Class 45 Rep 125 Posts Drives: 2020 m340i RWD Join Date: Mar 2016 Location: Maryland iTrader: (0) Garage List 2020 BMW M340i [0.00]	Emailed video to service manager and foreman, who thought it could be related to the AC system, specifically the compressor or the expansion valve. The noise is definitely not always there on shut down, and of course was not present when dealer drove it. They ran a scan for any fault codes with AC system, and finding none, returned the car and asked me to pay attention to how to reliably reproduce it. So far, what it seems like to me is if I idle the car for a while (10+min) or drive somewhat spiritedly with the AC on a low temp (working hard), the noise will be present about 30 seconds after I shut off the car. Sometimes it's been loud and goes on for 30 seconds or so, other times it kind of fades in and out at a much lower volume. And if I start the car again while the noise is happening, it stops. It kind of sounds like some kind of metallic resonance noise, almost like a tuning fork. So far, AC seems to be working fine. Really hoping it does not quit on me at an in opportune time before I have a chance to figure out what's wrong. Will definitely report back!
	Appreciate 0 Quote

07-25-2021, 06:02 PM	#4
transcendid Private First Class 45 Rep 125 Posts Drives: 2020 m340i RWD Join Date: Mar 2016 Location: Maryland iTrader: (0) Garage List 2020 BMW M340i [0.00]	Ok… pretty sure it's this pipe. After driving with AC on it, it is cold, has condensation on it, and I can feel it vibrating in tune with the noise. Does this help anyone narrow it down? Attached Images
	Appreciate 0 Quote

07-26-2021, 10:26 PM	#5
transcendid Private First Class 45 Rep 125 Posts Drives: 2020 m340i RWD Join Date: Mar 2016 Location: Maryland iTrader: (0) Garage List 2020 BMW M340i [0.00]	Quick update - dealer sent my videos to BMWNA who said they suspect the expansion valve is to blame and recommended replacement. Will try that and report back!
	Appreciate 1 Seaford1169.50 Quote

08-07-2021, 01:59 PM	#6
transcendid Private First Class 45 Rep 125 Posts Drives: 2020 m340i RWD Join Date: Mar 2016 Location: Maryland iTrader: (0) Garage List 2020 BMW M340i [0.00]	Expansion valve replaced. Knock on wood, have not heard the noise since.
	Appreciate 4 premier3is1637.50 Seaford1169.50 Montbason1.50 EXE462104.50 Quote

09-02-2023, 02:17 PM	#8
Montbason Registered 2 Rep 2 Posts Drives: 320i G20 Join Date: Aug 2023 Location: Mexico iTrader: (0)	Problem solved. Just changed the expansion valve under warranty and no more noise.
	Appreciate 1 EXE462104.50 Quote