Thanks so much for the help, everyone.
Ok, I pulled up the access compartment in the bedroom. The engine is directly below me. Then, after that is the fan blades, and then the radiator (newbie here; be patient).
Everyone has been talking about cleaning the engine side of the radiator. But if the fan blades pull the air in from outside, wouldn't all the junk be on the other side, the "road" side of the radiator?
I can barely see any of the engine-side of the radiator anyway. It's mostly blocked by the fan blades. But what little I can see, by pushing the blades around, the radiator looks clean to me. Can't see any kind of buildup of anything.
So, it's into the shop I guess, eh?
dave