Peculiar Noise

[lawnranger]

Hey everyone. I've got a 2002 Camry 4cyl. LE, 133K and only thing I've had to replace, other than tires is front brake pads at 118K, and a new serpentine belt 2K ago.
Something has been manifesting it's self over several months now, and still isn't effecting anything that helps me find it's source. When I pull up to a stop and sit there, the car will give a "whoop". It is kind of an accending "whistle", and can be soft, and sometimes it can be quite distinctive, and loud. It seems through trial recently that if I turn off the blower motor on the A/C / heater, that it doesn't do it, but I'm puzzled that anything involving the blower motor should cause such a noise. If I had to guess at what it is I would think it is a vacuum leak of some kind. But as I said everything works properly....at this point. Appologies if this has been addressed already, I'd have been the rest of the year looking through 514 pages of posts. Thanks for any help.

[Tech1984]

If I were you, I'd invest in a very cheap tool. A mechanic's stethoscope. Have it idle fully warmed up with ac on.
Now move over each area of anything spinning. Be careful and use common sense while doing this.
Pay closest attn to the water pump, ac clutch and serpentine belt idler pulley. How does the belt look? How old is it?

Oh, and welcome to TN!

[Glenn8963]

look for the vacuum reserve tank. sometimes these look like a softball. it'll be either under the hood, or in some instances up under the dash area. there will be a vacuum line attached to it. this tanks holds a certain amount of air to operate the vacuum doors in the a/c systems. on older cars, like an old ford or lincoln,they were used to store air for the hide-away headlights, and these looked like big coffee cans.

either the vacuum reserve tank is cracked, or the hose leading into it or exiting is cracked or loose. start at the tank, follow the air line in the engine compartment, since the serp belt was replaced, i'll be thinking the line got snagged, or cut.... check for cracks, burn throughs (heat melting it) etc. now, this WILL BE a plastic line, you cannot find new line easily, but to fix it IS easy...you will need a few inches of washer fluid hose. you slice off the bad plastic line, then simply fit a piece of the washer fluid hose over it. simple connection, you're done....BUT, you had better buy the correct inside diameter hose for a tight fit. you could take a section of the old plastic line to a parts store, and the guy there can try and stick that plastic into a hose for a fit. the tighter the better, to guard against leaks.

the "whoop" noise you are hearing is vacuum....