odd sound from engine compartment after driven hard

[kpl]

I only noticed this sound recently, kinda like a gear drive or blower. I've never heard this before, or since. It occurred a handfull of times, when we had short breaks between autocross runs, and was coming from the engine compartment. It didn't do it earlier in the day, when it was perhaps cooler and we had longer breaks between runs. You can hear it in this video.

http://www.vimeo.com/16012043

It only started at the end of a run and was dependend upon engine RPM, and not dependent upon the car moving. It went away after about a minute or two. It didn't last long enough for me to park and pop the hood and maybe get a better idea of where it was coming from. When I got home I took the accessory belt off to check the idler pulleys, alternator, etc. and they all felt fine. I replaced an idler pulley quite some time ago, which sounded a lot different (loud screeching, bearing self destructing sound) when it needed replacing. Any ideas?

[Loren]

Sounds like the air injection fan for emissions. Perfectly normal on US/Canada cars.

[kpl]

it's never, ever, been that loud before...I know what that normally sounds like and this isn't it, unless it's changed it's tune very significantly and gotten 50x louder. What do they sound like when they die?

Edited October 20, 2010 by kpl

[Loren]

If you hear the same sound when you first start car (from cold) then it is the air injection pump. If it is bad they usually sound like any other motor with a bad bearing.

[kpl]

If you hear the same sound when you first start car

nope, not the same sound, besides the sound of the air pump doesn't change with RPM does it

[kpl]

what's the procedure for draining, refilling, and bleeding the power steering fluid? I searched and couldn't find one.

thanks,