2003 Taurus SES Vulcan engine auto tranny 40K miles. I changed the Mercon ATF in the PS reservoir by using a 1/4" tube to siphon it dry. I did not crank it while the reservoir was dry. Refilled to proper level with Ford Mercon ATF and it whined like crazy. Asked a mechanic and he said whine due to air in steering fluid and said while racing engine 2000 RPM's turn wheel hard over to the right and left a few times. Did that maybe ten times but still whines.
Parked on a steep incline front up thinking maybe it would help air bubbles come to the top and turned wheel and raced engine but it still whines. Drove couple hundred miles, ten miles at 75 MPH, and still whining so got Castrol fully synthetic Mercon ATF and put in but it still whines. Seals aren't leaking and when I first got it it didn't whine, so something I did changing the fluid made it whine. Whine is worst when turning the wheel and other than that you can hardly hear it. Castrol been in about 300 miles now and the whine doesn't seem as loud but it's annoying.
Second shade tree mechanic said he thought the air should work it's way out and only thing he knows that would make it continue to whine is the seals are bad. But like I said, they aren't leaking a drop. Said maybe I should try Mercon V but that isn't what the manual calls for and don't want to do anything to damage the pump or seals.
Get the front wheels in the dirt so as not to wear rubber off them. Turn the wheel full right and pull it hard and hold it about ten seconds then do the same to the left. Do that about ten times and drive it and the whine should be gone. If not do it again and keep doing it until the whine is gone.