Chosen Solution
There’s a short (2-3 second) grinding noise at the beginning of startup, before anything appears on the screen. I’ve taken the cover off and the fan is rotating ok. Any idea what it might be? It works ok, just worrisome. Update (03/14/2020) I replaced the fan. It doesn’t work. I think I may have damaged one of the electrical ribbons, going to see if shop can fix. But also, still have the grinding noise. Video attached.
A grinding noise implies physical movement, and as the only moving part inside the Mac Pro is the fan that kind of narrows the possibilities.
