TM 10-3930-671-24 Fan NOTE If the fan has been installed backwards, about 50% of its cooling capacity is lost. The fan is designed as a "pusher-type’ fan, i.e.  to push air   through   the   radiator.      The   fan   blades   should   be installed  with  their  curve  to  push  air  into  the  radiator  as they turn in the direction of right-hand engine rotation. 1. Check for loose fan mounting screws. 2. Inspect fan blades for damage. 3. Check for fan installed backwards (This is a common problem).  If fan is installed backwards, remove and install correctly. F-98