Have a Landcruiser with Chevy V-8 and Chevy power steering system. The problem started recently, where the pump/pulley locks up when turning the steering wheel. The belt IS properly tensioned but squeals around the pulley when this happens. Have changed the pump twice and both hoses, but same problem. This setup has worked fine before, like for the last year & a half. What's wrong now. Has anyone experienced a blockage in the power steering gear box that might cause this?