Hey guys, today I noticed a strange noise coming from my trucks engine bay after he truck has been off for a while. I will attach a video but it sounds like a very faint whistle almost like pressure is being released from somewhere. It lasts .5-1 second and varies when it happens normally 5-10 seconds between. Has anyone run into this and figured what it could be? Thanks!

https://imgur.com/a/HpCVbAC this is the video - it is quite faint so you will have to turn the volume up

 

Are you sure it is coming from the engine bay (I couldn't hear anything in the video)? I had a very similar thing I noticed over a few weeks ago. Turned out to be the flex pipe just before the muffler while the heat dissipated. I have a video on here in a thread as well: https://www.f150forum.com/f2/weird-n...utdown-489941/

Isn't an issue, but definitely weird and annoying.

 

It seems to be coming from left side of the engine bay. I listened to your video and that sounded quite different. I'll try to get a better shot of mine but as a classic car problem it gets camera shy.

 

Here I isolated the sound from the video and uploaded it straight to the forum hopefully its clearer now.