Crankshaft Pulley Bolt missing

The squealing may be a loose or old fan belt{s). But the pulley should be removed anyway and inspected. The loose pulley may have wallowed out the bolt holes in it a bit and the pulley may not be flush/square against the pulley. Fjle or sand the mounting surface on a flat surface to get rid of any raised spots/burrs. The original bolts may have also been damaged and should be replaced.