Background: 2003 jetta; just changed rotors and pads on rear wheels a month ago, they are disc brakes
So the other day I was driving in a school zone at about 20 mph when I heard a VERY loud sound, like I’m dragging metal. i might also describe it as two rusty metal plates being rubbed against each other, but really really loud.
The noise is related to speed, it sounds cyclical and speeds up as the wheel turns faster. It occurs when I am NOT braking.
I parked the car and came back to it a few days later move it and the sound disappeared for the first 100 feet and then came back.
UPDATE: we did 2 things - we changed the caliper, and we also noticed that a caliper bolt was missing. I am pretty sure the noise was coming from that missing bolt - i think the caliper became dislodged and was making contact with the rotor. The caliper also seemed to be dragging a little bit so we went ahead and changed it too.