So, a brand new problem, trying to tack it down. A few days ago, and today, while coasting around 40-50 the mkz starts emitting an at first faint but today very loud whistle/whine/squeal. Tapping the brakes will end it while the brakes are applied. Accelerating up or slowing down around 30 seems to end it. And its intermittent. It just pops up. Newish pads and rotors. Calipers were cleaned up and greased when I replaced them. AT fluid was looking like it needed to be changed for sure. Too cold to put the car up and take off the passenger side wheel and well panels to get a better look at the tensioner, pulleys and belts. Anyone ever ran into this one? The google rabbit hole is driving me nuts.