What could be making a swishing sound from the front wheels on my MKX?

Wiggle all the splash guards in all four fenderwells to make sure one or more is not falling off, has lost clips or whatever holds them. They may look OK to mechanic but rub tire when in motion. Do the same with fan shroud...the source of where the sound is coming from can fool you and may not be even wheels. While at idle no sound ...but that little tiny bit of torque on engine when accelerating maybe, just maybe could throw something off.

Thank you for your reply. I found that actually a couple of clips are missing from front tire fenderwell so hopefully that is the culprit. However the fenderwell is not scraping the tire. Do you think it might be catching the wind?

Very well could be.

So.... after many hours at the auto repair, the mechanic has found that the swishing sound comes from the new brake pads that THE LINCOLN DEALERSHIP placed on my car about a month ago. The pads were to thick and were constantly rubbing on the rotors. The contact was so close on one wheel that it didn't even spin. Thanks to the good ol' LINCOLN DEALERSHIP!!!! Need I say that I will never trust another dealership again for Auto work!!!

OK, I was wrong..that was my best shot. You said you just had brakes done at dealer, so dismissed that...my bad. I am very happy to know that the problem is ID'ed and fixed, thank you for the update

Thank you Tracy, I had the caliper changed as well, I will take your idea about the O-ring to the mechanic and hopefully he can work with that idea in mind. Thank you!

You are very welcome!

I’m so sorry that you listened to this idiot and wasted your money. It’s a tragedy how many people have ZERO idea how cars actually work.