92 Power Steering

Can any jeepers out there explain to me why a rebuilt p/s pump complete with reservoir, bought from Auto Zone, would squeak while engine is running at idle? I just installed the unit about 2 days ago. The parts guy at the counter sais it takes time for the new fluid to work its way into the bearing/ ?? ?
Jeff

They do "sqeal" , but that should be worked out over nite after the bubbles rise to the surface. If it takes that long , than the bearing is running dry, and that would kill the pump.