Anyone figure out the high pitch whistle sound when shutoff?

[Badgertits]

not sure if anyone has noticed yet but our (i would say my but after doing some research seems this prevalent) trucks will emit an intermittent high pitch noise from the engine compartment that lasts maybe 1/2-1.5 seconds, goes a few seconds in between, & will go on for hours after the truck is shut off. Will happen even when battery terminals are removed. Sounds like a combo between pressure being released or electronic capacitor type sound, but I’m def leaning toward mechanical & some pressure release.

I am unable to load the video I took of it, but sounds 1000% identical to this:

Now after browsing the internet/forums seems like this sound is coming out of multiple different F150 platforms- HO 3.5, reg 3.5, 2.7 & even non boosted 5.0- & also seems like nobody has answer for it. My truck runs fine, & seems like there isn’t any failure or other problem associated w/ it but I really would like to know wtf it is!!! I THINK it’s either a vacuum line or high pressure fuel rail/pump releasing air? Seems to happen more when weather/temps fluctuate but I have heard it in summer too I think.

 

[Lasercat]

I have the same damn thing. Asked about it here a couple years ago, and nobody had any ideas. Recorded it for my mechanic, he had no idea either. Eventually I just stopped worrying about it.

 

[Badgertits]

I have the same damn thing. Asked about it here a couple years ago, and nobody had any ideas. Recorded it for my mechanic, he had no idea either. Eventually I just stopped worrying about it.

Based on the number of “dead end” threads I’ve found on forums & vids on YouTube I’ve pretty much come to the conclusion it’s “normal” - BUT I’d still like to know wtf it is lol!

I hadn’t heard it/forgot about it for a bit then heard it after loading tune & was like “damn I should’ve brought the truck in to dealer to check this out beforehand” but at this point I don’t give a damn as far as that goes b/c it seems very common & have not found any instance where someone claimed a problem/issue related to it.

Since I’ve confirmed 5.0 F150s have exhibited the same thing I gotta rule out anything turbo related. Vacuum or high pressure fuel system my best guess.

 

[isis]

I’m sure it’s the high pressure fuel system.

 

[CigarPundit]

I hang out in the garage A LOT with my truck right there, often after I have just parked it. Mine has never done this that I have heard. Weird.

 

[Badgertits]

I hang out in the garage A LOT with my truck right there, often after I have just parked it. Mine has never done this that I have heard. Weird.

FWIW- I typically don’t hear it in my garage most of the time it’s outside so not sure of barometric pressure or temp plays a factor. I’ve read it occurs more often in wet conditions but who knows.

 

[CigarPundit]

Ah, well so far mine hasn’t seen either rain or humidity.

 

[Lasercat]

It's not even a "right after you park it" kinda deal. I've been near the truck 4 hours after parking and the sound comes out of nowhere.

You know what... first time I heard it was after climbing about 5000 feet into the mountains. Other times it's during hot summer days. I'm wondering if it's a fuel system pressure release valve? That would seem to make perfect sense, and I can see how a tiny manufacturing difference in such a valve could cause some trucks to whistle and not others...

 

[Badgertits]

It's not even a "right after you park it" kinda deal. I've been near the truck 4 hours after parking and the sound comes out of nowhere.

You know what... first time I heard it was after climbing about 5000 feet into the mountains. Other times it's during hot summer days. I'm wondering if it's a fuel system pressure release valve? That would seem to make perfect sense, and I can see how a tiny manufacturing difference in such a valve could cause some trucks to whistle and not others...

Yep definitely seems like there is some sort of correlation between temp/weather/atmospheric changes & the sound, at end of the day consensus seems to be lots of F150 owners have noticed it, it can happen across the whole engine lineup, & nobody has reported any ill effects or problems as a result.

I bet ALL of em make it & some people either just haven't had the opportunity to hear it, or CAN'T hear it either because of the pitch/tone of the sound, the faintness, or their own bad hearing. Like in other words, maybe on some trucks the pressure release is so minimal or the valve/hole or whatever from where its being emitted is slightly different shape or angle or whatever from truck to truck that it could be nearly inaudible or maybe instead of having multiple spread out whistles/releases you just get 1 long one & if you're not there to hear it you wouldn't know. if a tree falls in the woods & nobodys there it doesn't make a sound.

 

[Booth9999]

That’s wired mine sounds more like a modem connecting noise so I’ve always thought it was the truck trying to connect to the internet lol. Interestingly enough mine does it almost every time I shut it off at home but have never heard it off of the mountain and I live at 5700ft.

Side note as I think about it, mine has not done it since I had the updated valve covers installed BUT it has not been hot since then.