Power steering/Hard to turn

[Napu(StrongWave)]

I have a 2001 sport trac 4.0L sohc v6 2wd.

Problem is when the truck is stopped its hard to turn the wheel,same like when the truck is turned off and you try to turn.. I have had a little agravting noise from pump for a while. Couple of days ago i did a 360 in the feild nothing high rev or fast at all, but i did have the steering turned all the way to the lock.. Shortly after that the problem with the steering occurred.

I want to know if anyone else has had this problem before?

 

[Napu(StrongWave)]

I just changed the power steering pump. Cleared up well until 3 miles down the road. It is doing it still not as often and not as hard to turn..

 

[Napu(StrongWave)]

MUst of had air or a blockage in the line. Everything works good now.