tuffluck

iTrader: (4)

my car has been having an intermittent problem with a very loud hiss/whine that seems to start when the car warms up completely, but it isn't always present either. i don't know if it's a belt whine or a vacuum leak whine or what. it's so loud that even making this video was hurting my ears once i walked in front of the open hood. one drive around town and it's hissing, two hours later i do the same thing and no noise. i don't know what it is.

also, my AC has been blowing on the feet randomly which i am told is a vacuum leak, so i'm wondering if the two are related. can you tell what the noise sounds like to you? i tried to turn a flashlight on in the video but that doesn't really help much... thanks.

http://www.youtube.com/watch?v=-GvjYHXnfgE

conor.davis

iTrader: (20)

If you give it a tiny bit of gas does it go away?
Kind of hard to tell from your video, but I've heard a somewhat similar noise coming from the IAC opening up a lot. IE no hole/properly adjusted TB blade.
Can you figure out where the noise is coming from? put your head by the lid and see if its louder there.

tuffluck

iTrader: (4)

it is so loud that the direction of where it is coming from is indistinguishable. it doesn't go away if you increase the rpms, it gets louder. how do i check the iac like you mentioned?

mwg2600

It is hard to tell from the video. The first thing i would do is to take the belt off, and start it and see if the noise goes away. don't let it run for more than 15 seconds without a belt.
Your comment about the a/c and the vents switching makes it sound like you might have a vacuum leak somewhere.
I would start by ruling out the belt and the accessories first.

tuffluck

iTrader: (4)

does it sound like a pulley or too high pitched? belt is what i was kind of thinking, that or maybe a leaky exhaust manifold gasket or something. that'd be really tough to diagnose, but seeing as it only makes the noise occasionally, i don't know if exhaust leak is as likely.

technical

Fastest way to check for a vacuum leak is with a vacuum gauge. Your sig suggests a stock engine. You should be able to pull at least 18" or very close to it.