because its only when its turning slow one direction its not a cv joint or bearing. if it was a cv joint youd hear ticking when driving. If it was a bearing... youd know it was a bearing. Like the car pulling hard to one direction and lots of noise and very unsmooth ride.
check for a leak when it come to the power steering check for a leak. mine has a small leak, and if not attended to it could get worse and then cause problems. typically on BMW's they leak around the hose clamp up near the PS resevoir.