1999 Cadillac DeVille steering problems

I have a 1999 Cadillac DeVille. Excellent car. The other day a problem started with the power steering; as long as the car is moving and i want to turn left or right there is no problem; however when i put on the brakes and begin to turn RIGHT....the car just simply acts as if it has no power steering at all. Turning left is fine. Backing up is fine; i can turn the wheel left or right. The problem only occurs if I turn to the right while slowing down or placing on the brakes. I checked the fluid yesterday and it did appear low so I filled it up to the line. Still have the problem. I am not working now and do not have the money for any major problems. Please help me figure this out. Thanks:banghead:

My 98 Deville PS pump went out at 100k miles and did some of the things you mentioned, although mine went out totally, the pump started making a loud vibrating noise when turning the wheel left or right. It went out to where I had no power assist at all, then all the noise. I put on an Autozone pump and it was bad, didn't have enough pressure to assist, a second pump solved the problem. If you suspect the pump, I'd replace the pump, they are pretty easy to do and cheap, teh AZ pump cost about 70 bucks and they are easy to change, except for changing out the pulley, that can be a pain.