Hyundai Forum - Hyundai Enthusiast Forums - power steering binding noise

I have a 2003 Santa Fe and after driving it for 15-30 mins. the steering starts to make binding feel/noise when you turn the steering wheel in either direction. Also I notice the fluid in reservoir is foaming after I turn it off. So far I've done the following with no cure yet:

drain the system and added correct fluid from the dealer (noise went away for a week but then came back).
added an additive to the fluid (noise went away for a few weeks but came back again).
poked a hole in the filter inside the reservoir to see if it was clogged (still foams up).

The only thing I can figure is that the pump is bad.
Any help would be appreciated!