Yes, soak the impeller assembly seperately, key things to check are- is the upper bearing stuck to the magnet, this piece is under the magnet at the bottom of the well and a red oring is underneath it. The magnet should spin freely on this piece. Also, is the hole in the center of the magnet obstructed, water is pumped down through this hole to cool and lubricate the pump. I would avoid dissassembly unless necessary beyond this point.