I have an 82 Caddy w/1.9 AAZ diesel. Recently I developed an over heating issue when it is under load such as climbing long hills or any under boost conditions. I have changed the alt and A/c belts, bottom radiator hose and hose return from rad to coolant tank. Also flushed the cooling system with Prestone flush. About the time I changed the belts and return hose is when the problem started. The other changes were to address the problem. Also I have retightened the belts to bow string tight. I have even used belt dressing just in case it was a slipping problem. I did use a 5/16 fuel line hose for the return hose but the water seems to me to be returning OK at least at idle. Any ideas 'cause i'm out of them.