[KeninCanada]

Ok, here's my take on your problem.

I own a '99 Windstar. About one year into ownership I had a scary power steering noise under warranty. Right off the bat Ford service manager recommended a change to the flexible power steering hose under warrenty?? Guess what, it worked for about 4 years (100K+). Then the same noise came back and before I could fix it the hose ruptured on my wife. She drove it home (arhh!) and about one year after the hose was replaced I needed to change the rack.

I had explained to me that the noise I heard, and I suspect you hear, is the pump cavitating. Basically it is starving for fluid and pulling air. If you check the fluid level at idle and it seems fine (i.e. you have no room to add fluid) but the sound it there when you turn the steering wheel I suspect the rubber hose is flexing increasing the closed system volume, cavitating the pump. Try changing the hose. About $70 for the part plus labour.

BTW after I had the rack changed the caviting sound hung around for about one week. The mechanic suggested that I needed to purge the air pockets from the system by turning the wheels lock-to-lock several times. Eventually this worked. Everything is fine now.

Good luck
KeninCanada