Strange whistling sound

For the past few months I've been hearing a strange whistling sound from my '96 Tacoma. It doesn't happen on every drive but when it starts it occurs every few minutes or so. It sounds sort of like someone whistling to call someone - something like a wheee-ooo-wheet. Just one short whistle repeated every few minutes or so without any regularity.

Attempts to get it to whistle when revving the engine with the hood up have failed. All of the hoses are in good shape and the drivability of the truck is not affected. I did replace the thermostat with a coolant replacement 6 months ago, but don't recall that the noise started soon after that. I did have a Fiat 128 that developed sort of an occasional whine that turned out to be related to the heating control, but messing with that on the Tacoma doesn't seem to effect any change.

Any ideas? Thanks.

 

Ask your friends where they hid the noise maker?

 

And check PCV grommet. Mine developed a whistling sound after and only at times while at highway speed under load. Had already replaced vacuum hoses so was sure it wasn't that. After rechecking things several times noticed oil residue around grommet. Replaced and no oil residue or sound afterward. Could also be an idler pulley?

 

Easy enough. Thanks.

I'll poke around the PCV valve to see if I can recreate the noise. I am planning a valve cover gasket replacement is on tap for the Spring and I planned to replace the pcv valve as well. I'd expect that an idler pulley would give me a more constant whine, but I reckon it's possible. Thanks.

 

https://www.youtube.com/watch?v=eSOSJ68xOBA&ab_channel=RyanMiller

 

Ya, no

 

My Civic has a whistle at highway speeds that I think is coming from my wiper blades. Could be anything that catches air the right way.

 

Wow, it's a good thing that this fad did not catch on. Pretty obnoxious.

I don't think my occasional whistle is related to wind. It occurs at any time and at any speed, from 2 mph on up.

 

I used to teach High School, ran a computer lab where my students worked on courses online Independently. I have one of those Fart Machines with a remote.
Used to hide it under one of the desks hidden in all the wiring, I'd set it off occasionally. Funny as hell to watch the kids try and ignore the sound or try to not look around
for the "source". Hard not to break out laughing. What the hell, the good old days.

 

It's probably the electronic tracking device your wife hid in your truck to check up on you.

 

Brake booster leak?