"TANDDANDBIGE".....There is a great replacement for your Roadmaster rear radiator fan. Source Engineering sells a fan blade that "returns" 25HP to the ISL engine and 40HP to the ISC engine. The fan blade is more aerodynamic and doesn't look anything like the big poorly designed blade you have now.
They cost about $650.00, but you'll appreciate the power increase. The ISC blade returns more power because the ISC engine spins faster than the ISL. I installed one on my Diplomat many years ago and would do it again. It was a great product for increasing power, especially acceleration. Cooling doesn't change.
The only con.....since the OEM fan is so big and poorly designed, it actually helps you slow down some when using your exhaust brake, but wasn't significant enough to warrant not replacing it.
Source
Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab