we ran the spreaders last year and had nothing but trouble with them because they made the combine heat up because they would not throw the straw away from the combine.
the trouble that we were having is that the spreaders would throw the straw on and around the rotory screen instead of back and away from the combine. then what would happen is the straw would plug the radiator and the fan would not be able to pull the air throught and across the engine.
There is a rotary brush kit that bolts onto the air duct, this breaks the straw up and with a kit to increase the vacuum off the screen this should stop the screen blocking and causing your engine to overheat. Also check the duct inside your fan shroud to make sure it hasn't sucked in causing a drop in vacuum on the screen