I have a '99 zx2 5-speed Escort, I just started driving a longer distance to work and after about 30 minutes I start getting a whine fron the engine compartment. It seems likea constant high pitched whine at all speeds, gears, and rpm's. When I depress the brake pedal (even just a little bit) the whine is reduced or quits completely. It also stops when I come to a complete stop at an idle. The car has 88k and runs fine other than this. I was thinking it was a small vacuum leak but I wasn't sure.

Anyone have any suggestions? Thanks for your help.