Power Steering

Hello. I am sorry to see everyone having so many problems with their Malibu's. I purchased my 2000 well used without any research into the vehicle. I love the way it handles (handled) and it sure moves. It has become one problem after another though. Yesterday my power steering went without any warning. Well, maybe a little. A couple times in the last week I noticed just a hint of stiffness when first starting out but it went away very quickly. I wrote it off to the extreme cold. There is no fluid leaking so I am inclined to think it is the rack and pinion. I have been told it may be a valve in the pump. Does anyone know how to check this or if it sounds right? Thanks for any help.