Engine Whine - Power Steering Problem?

[LarryGreen]

My 96 has been making this whine when the rpms are over 2000. The whine varies with engine speed. At first I thought it was a transmission problem, but the whine also occurs when the car is in park and the engine rev'd. I popped the hood, rev'd the engine, and the whine sounds like it's coming from the power steering resevoir area, so I removed the power steering pump belt, reran the engine, and the noise is gone. In addition, I've been losing power steering fluid from the cap - it foams up and out of the cap. I noticed this when I rev'd the engine.

Would the O ring fix maybe fix this problem, do you think maybe I need a new pump, or could it be something else? I'm going to try the O ring fix this evening but any advice would be appreciated. By the way, exactly what is an O ring (I want to know what I'm looking for when I stop at the local Pep Boys on the way home)? Thanks.