steering groan when warmed up

[landrovered]

I drove about fifty miles yesterday evening and upon my return home I noticed a groan on the front passenger side when I turn the steering wheel to the right about 15 degrees it does not do it to the left. I noticed this noise once before and checked and topped off the power steering fluid with Pentosin, it was not really low. I have only driven short trips since then until yesterday I though it was just the fluid. On short drives it does not make the noise but after running for an hour or so it is making it.

I am going to dig in to the problem this weekend and am looking for some items to check. There have been no drips in the driveway and does not appear to be leaking fluid. Any suggestions appreciated.