My '72 El Camino 350 power steering has for a while been a little rough first thing backing out of the driveway in the morning, then fine. Last few days it's starting to do the same all the time when going slow, like parallel parking. Turning the wheel it sort of pulses, hard, easy, hard easy. Also makes whine when all the way to one direction. Belt fairly new, and tight, no leaks, fluid full. Should I just replace the pump?