On a 240 there is no fan clutch so it will always turn the pulley. Perhaps the water pump is seazing up or did you check to see of the alternator belt is slipping? A slipping belt will make a hellofa racket.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.