Toyota Repair: steering problems, power steering fluid, hydraulic problem

Question
I have a 1999 camry with 260,000km and just recently my steering will seize up making it very difficult to turn the wheel. There is no evidence of any leaking, and my power steering fluid is fine. I had the p/s pump motor changed with a rebuilt one thinking that was the problem, but still a problem. One Toyota mechanic told me it could be the u-joint. There is no noise when I do turn the wheel, and certain times when driving are worse than others. When I'm in park, it will turn more freely. I have been told that with rack & pinion problems there would be evidence of a leak. Any suggestions?

Answer
There doesn't have to be a leak for there to be a problem, the could be an internal valving problem, a mechanical problem would be more consistent and not vary, a hydraulic problem can be intermittent, I would recommend replacing the power steering gear unit.