I'm suddenly occasionally getting an intermittent short high-pitched whistle, seems to be related to my my a/c, but I even get a little one after the car turns off. Anyone else experience this?

 

if it changes pitch as you turn off/on the AC, I'd suspect one of the serpentine belt idlers or perhaps the AC compressor clutch. You'd have to remove the serpentine belt and feel the idlers to check.

 

Thanks. I actually get a little of the same sound after I turn off the car completely, and it's intermittent enough that I'm pretty sure it's not related to the under the hood parts. It seems like it's caused by leaking air somewhere, and it only happens when it's really hot.

 

are you losing any coolant? I'd suspect it cool be associated to the vacuum pump/booster. Next time you hear the sound with the engine off, try pumping the brakes to see if it changes anything.

 

Remove and tighten coolant tank cap, ensure coolant is right color and topped off. Check thermostat area for leak or loose hose cracked housing. Test thermostat.

 

Thanks everyone, I'll take a look at those things.

 

So it turned out to be the a/c thermal expansion valve.