Hey I have had that problem for a long time and I replaced the powersteering pump and I still got the noise. It is when you turn it to full lock correct. Well the noise continued to come back on and off sometimes it does and sometimes it doesn't. Well I recently had my car in the shop and had them replace all of the belts and change out to fluids. When you change out or add Power Steering Fluid you need to remember to have someone sit in the car and turn the wheel back and forth to full lock while you slowly add it because sometimes you will give air bubbles causing that sharp and lock screech. When I changed the belts I no longer had the problem so I would more than likely say that your belt is loose now remember when tightening that be careful because if you break the tensiorner bolt(which is EASY) you must buy a new assmbly b/c they dont just sell the botl and it is reverse threaded. If that doesn't fix the problem call me

314 226 3776
I will try and help you figure this out good luck.