Just recharged my AC system have not used it for 2 years. Now when I run the AC the engine overheats. I have done the following. Flushed the system. Removed the thermostat and filled it up and ran it with the upper hose off at the radiatior and water flowed out, proving the pump was pushing water around. I put in a new thermostat all of which has no effect ,still overheats. Next step is a newradiatorI guess.It is theoriginal (17 yrs old)but does not look dirty inside,I am stumped. Proir to this we have a long grade up a mountian and when I would go up it it would overheat. Any thoughts?

 

Sounds like your radator. It might have a pin hole leak. You might not see it but it might not let it hold any pressure. Take to to get repaired. Or better, geta new one. You might also have a bad fan cluch. I would buy a small eletric fan to help you on those hills.

 

pressure test the cooling system. radiator may have a small leak or the cap may not be venting properly. also check the coolant temp sensor

 

I am putting in a new raditor today. Don't know what else it could be. Not a sensor issue it overheats and boils over. I think 17 years of build up inside it is the problem.

 

New radiator in. While the old one looked good from the engine side when I took it out the front side that I could not see because the A/C condenser was in theway was toast. 40% of the fins were eaten away like they were attacked by termites. I guess it was 17 years of exterior rotting.