Whining/Scrubbing type Noise Under Hood HELP!!!

[clcga]

HELP!!! I have a whining / scrubbing noise coming from under the hood of my 98 Montero Sport (95,000+ miles). I have been told that it sounds like the power steering pump but then my mechanic told me no, it wasn't that. He thought it might be the pulley that the timing belt was on...well guess what...he tore it completely down and checked every belt, pulley, barron, nut, bolt etc and could find NOTHING!!! Some days I'll hear it from the first crank up and some days I won't hear it at all. I have plenty of power steering fluid, too. HELP!!! It is really driving me insane to not know what it is. It is really more of a whine than a scrub sound. And no, I haven't taken it to a dealer yet b/c last time something was wrong they tried to ream me a new one. HELP !! HELP!! HELP!!