Just remove the front accessory belt and start it. If the loud squeal is gone you shut off the engine and start hunting on the accessories. If the squeal is still there then you have a worse problem, the description sounds like a metal on metal issue, but it could easily be something like a stuck alternator or idler and what you hear is the belt dragging on it.
How about this, take a video of it and post it. That alone would help. Then shoot a close up video showing the drive belt and as many of the items it drives like the idlers, alternator, power steering and such with the engine off, that may also help.
Friday, April 16th, 2021 AT 8:46 PM