Beep/whistle after driving when engine is off?

[Unfortuitous]

The other day after a short drive, I had a beeping/whistling noise that sounded like it was maybe coming from the front of my gas tank. It started about 10 minutes after I shut the engine off, and I heard a chirp that would repeat every 15-30 seconds. Intervals didn't seem to be consistent, and it continued for a couple of minutes, probably beeping maybe 15 times or so total. It hasn't done it before nor since.

I have a 2.3L manual.

Posting a video of the noise. It sounded very much like an electronic beep from afar, but as I got closer to the source, it sounded like it could possibly be a whistle.

Anyone ever see or hear of anything similar? I am stumped. Thanks for taking the time to read my thread.

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[RedRider]

It's not just you.



https://www.f150forum.com/f118/whistle-sound-when-truck-not-running-412016/index2/#post6029741

In that instance, there is some speculation it is this:

SSM 50445 - 2017-2021 F-150 - High Pitched Squeal/Whistle Noise From The Engine CompartmentAfter Engine Shut Off - Built On Or Before 01-Feb-2021 Some 2021 F-150 vehicles built on or before 01-Feb-2021, 2017-2020 F-150 vehicles equipped with a 3.5L EcoBoost engine, 2018-2020 F-150 vehicles equipped with a 2.7L EcoBoost or 5.0L engine, 2019-2020 F-150 vehicles equipped with a 3.0L diesel engine may exhibit a high pitched squeal or whistle type noise from the engine compartment after the engine is shut off. This condition may be due to the air conditioning (A/C) low side system pressure exceeding the high side pressure resulting in equalization of A/C system pressures through the A/C compressor. An updated A/C compressor has been released to resolve this concern.

So obviously not exactly that because it's a Bronco and not an F-150, but maybe something along those lines, like a similarly faulty A/C compressor? You said it hasn't done it before or since? Maybe try taking some short drives with A/C on and off to compare to help narrow it down. Is your A/C performing ok? Is there enough refrigerant? That thread I linked may give you some other leads to chase down too.

 

[Unfortuitous]

It's not just you.



https://www.f150forum.com/f118/whistle-sound-when-truck-not-running-412016/index2/#post6029741

In that instance, there is some speculation it is this:

SSM 50445 - 2017-2021 F-150 - High Pitched Squeal/Whistle Noise From The Engine CompartmentAfter Engine Shut Off - Built On Or Before 01-Feb-2021 Some 2021 F-150 vehicles built on or before 01-Feb-2021, 2017-2020 F-150 vehicles equipped with a 3.5L EcoBoost engine, 2018-2020 F-150 vehicles equipped with a 2.7L EcoBoost or 5.0L engine, 2019-2020 F-150 vehicles equipped with a 3.0L diesel engine may exhibit a high pitched squeal or whistle type noise from the engine compartment after the engine is shut off. This condition may be due to the air conditioning (A/C) low side system pressure exceeding the high side pressure resulting in equalization of A/C system pressures through the A/C compressor. An updated A/C compressor has been released to resolve this concern.

So obviously not exactly that because it's a Bronco and not an F-150, but maybe something along those lines, like a similarly faulty A/C compressor? You said it hasn't done it before or since? Maybe try taking some short drives with A/C on and off to compare to help narrow it down. Is your A/C performing ok? Is there enough refrigerant? That thread I linked may give you some other leads to chase down too.

Thanks for the reply and the lead. Although the noise in my bronco had a very consistent short length, it does sound very much like most of the whistling examples in that thread. It also was just short beeps, one every 15-30 seconds, and the time interval between beeps/whistles was not consistent ( the last few beeps had a minute or so between them)

Strangest thing is that it did it after a very short drive and I know for certain that the entire air system was off for the whole drive - no heat, no AC, and not even the cabin fan. The weather was roughly 67 degrees too, so not extreme in either direction.

One poster said it turned out to be his fuel pump, and that does check out given the location where I found it the loudest seemed to come from inside the front of the gas tank on my Bronco, but everyone else in the thread is speculating that it is likely the AC system balancing pressure, and the AC drain hose is right in that vicinity too, for reference.

Either way, it seems like there is not a definitive consensus on what exactly causes it, although Ford believes it is isolated to vehicles built in 2021 or earlier, which makes my case on a 2024 model even more perplexing.

 

[UncleBrad]

I know this sounds like a stupid question, but do you have a portable refrigerator or some other kind of accessory plugged into the 12V outlet in back?

 

[Unfortuitous]

I know this sounds like a stupid question, but do you have a portable refrigerator or some other kind of accessory plugged into the 12V outlet in back?

Not a stupid question, but no, nothing is plugged into the vehicle and everything electrical is pretty much stock.

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