Since we had replaced the engine coolant thermostats it was time to move onto the radiator which on our 4905 is located on the left rear of the coach. Since our cooling fan is direct drive and our louver system is disabled in the open position, the only thing standing between us and efficient cooling is the radiator. I wish I would've taken more pictures as the mud and sand boiled out of this thing but you'll just have to imagine it. I would estimate that this perfectly clean looking radiator core was holding at least five pounds of crap. I cleaned row by row paying close attention to my angle of attack so as not to damage any of the delicate fins. After about four full passes, I unbolted and hinged the louver assembly out of the way and started all over until the water ran clean. Took about a half an hour to completely clean the core but it should make a huge difference in cooling capacity.