Diesel pusher overheating

Yes on the rear radiator. Did clean the rad and CAC from the front to the back but water looked pretty clean. Spoke with the previous owner who bought the coach new and he had intermittent heating issues even when new. He tried rigging up some dryer duct with a wall mount dryer vent to bring air in to the engine compartment. I removed this setup as it seemed to me pulling hot air from the roadway was counter productive to cooling. I am hoping to open a dialogue on the positive vs negative effects of a good high flow electric fan mounted on the rear/away from the engine side of the radiator. Would this increase the available air flow available to the radiator and engine mounted fan ? Or would the electric fan impede available flow by blocking part of the radiator. Any thoughts are appreciated.