Agree that a a/c coil cleaner is a good product to use but you need to be sure it's NON-ACIDIC. I used Nu-Brite by Nucalgon. It's available at big box stores and Amazon.
The company says, "Nu-Brite is a non-acid, alkaline-based product for cleaning and brightening air cooled condensers. It is formulated with the best available foaming detergents and chelants to quickly penetrate and dissolve greasy dirt and grime and foam it right out of the coil. The safer alternative to acids."
I spent about an hour with the hose and low pressure fan nozzle to clean the radiator on my 2014 Rancher 420FM. I did not remove the plastics. I THOUGHT it was fairly clean because I could see through it on the sides. Looked again using halogen flashlight and it was still caked with red mud. I tried Simple Green and washed and rinsed over and over. THOUGHT it was clean.
When I removed the old plastics to replace with new ones I realized that radiator was no where near clean!
If you want to do it right, you have to removed the front rack and plastics. Removing the radiator is not difficult.
Attached pic shows how much mud foamed out after I thought I it was clean.
