Nelsonea, hey another member pointed out a possibility on a different post!

X-wrench stated in another cooling issue about debri build up between the A/C condenser and radiator causing issues, that to could be a possibility in your situation less the build up and more the condenser fins full of debri. When you changed the Radiator was there anything between the two?

This happens in the desert with military equipment alot, the set ups are different mostly but the issue the same! We do not see it as much around central NC any more mostly due to everything is payed now and manufacturers have revamped the openings in which air flows, to be more directional with less openings for air/debri to travel around the condensers. This does lead to condenser build up which in return clogs the flow to the radiator as well!

In years past however build up between the two was a common thing to see. We, my family that is own a salvage yard and from time to time I still pull a A/C condenser that has clogged fins due to bugs, road grime, trash and a small build up between the two parts.

Might be worth a look!