I wonder if that foam would clean the radiator?
I was just up on the roof cleaning the ACs. The units we have have a plastic compartment for the front part of the AC, where the air passes thru the exchanger to cool the air. There were numerous screws missing creating a gap where outside air was entering the system. I replaced the missing screws and then used packing tape to positivily seal the small gap remaining. Will let you know how it works next trip.