I see that this post is from 7 years ago but I want to share my similar situation. I have a 2012 Ford edge limited 3.5 v6. I had a leak in the high pressure power steering line from Gear to pump. Very small just a couple drips a week. I bought a duralast line to replace it from auto zone. Ever since the line was replaced my pump has whined. 3 mechanics and a dealership later no one could figure out why. It was bled multiple times. No air bubbles, no foaming, power steering worked totally fine and no leaks but the whine wouldn't stop. I saw this post and took a chance. Bought a motorcraft line and replaced the line again. The whine totally went away. Something with the aftermarket line must be different (length, inner diameter, etc) to cause the pump to caviate. So if anyone ever has a similar issue, buy motorcraft parts and don't trust aftermarket
