94 f 150 300 ci stick. my son just learning to drive stick...lol.....the fan has trashed three radiators......the mounts have been replaced, all three. what could be going on? crossmember seems tight.

 

Should be pretty obvious when it hits the radiator...High or low rpms? Is there enough clearance at idle? I would say that the rubber mounts are shot but you said you replaced them. Not many options to think of. Correct fan? The higher the rpms the more sucking power the fan has so maybe its pulling the radiator in just enough? You sure its the fan?

 

The fan shouldn't be anywhere close to the radiator. Do you still have a fan shroud on the radiator?

 

Just for a joke grab hold of the fan (motor off of course) and see if you can move it back and forth. Maybe something in the clutch is shot and when the fan gets some RPM's it's moving foward.

But that is just a guess.
Good luck

 

The fan is pretty close to the radiator on a pre-97 inline 6. The OP posted this in the wrong forum.

 

Truck ever wrecked? Condition of motor mounts(engine not fan)? Oem fan or aftermarket? Lots of variables to look for.