new here. Pls help with strange 'psssshhh' sound

[Kool Hand Kook]

Hi folks,

My 2001 4Runner makes this weird sound from under the hood when I'm driving. The garage can't figure it out, because of course it never happens when they have it. But the best I can describe is when I'm driving at highway speed I will hear a weird 'pssssshhh' sound that lasts for about three seconds. If you let the air out of a compressed air tank for three seconds that's what it sounds like.

The truck has 330,000 miles and it runs fine, the sound has no effect on how it runs, but man that sound has me concerned.

I've searched this forum but I haven't found an answer.

thanks in advance for your help folks.

 

[absalom]

Blow off valve?

Grab your cellphone, take your truck for a drive, record aforementioned sound, post to YouTube, embed said YT vid to your original post, and sit back while a bunch of bored, stuck at work, middle-aged men, attempt to diagnose your sound via the magic of the interwebs.

 

[shootmymime]

Blow off valve?

Grab your cellphone, take your truck for a drive, record aforementioned sound, post to YouTube, embed said YT vid to your original post, and sit back while a bunch of bored, stuck at work, middle-aged men, attempt to diagnose your sound via the magic of the interwebs.

because we all know how crappy sounds actually turns out with videos.

 

[JayRolla]

Blow off valve?

Grab your cellphone, take your truck for a drive, record aforementioned sound, post to YouTube, embed said YT vid to your original post, and sit back while a bunch of bored, stuck at work, middle-aged men, attempt to diagnose your sound via the magic of the interwebs.

You just explained me to the tee!

 

[absalom]

You just explained me to the tee!

You sound dreamy

because we all know how crappy sounds actually turns out with videos.

Well, it's either that, or we play Clik n' Clak while OP makes mouth sounds of his truck via text.