Well all that dried mud will act as an insulator for sure. It might help if you clean the radiators with water. The mud will be caked in between the fins, cutting dwn the air low considerably. You have to be carefull though with your water pressure, or you will bend a lot of fins. The safest way IMO is to hose it down, let the water penetrate the mud for a bit, then hose it down again, repeat untill clean. Or you could just take out the rad to clean it; would also give better access to the air conditioning condenser.
How can you trust an atom, they make up everything