The water passages are very narrow and is proabily pluged from gunk.I took mine off and poured radiator flush let sit for a day of so and then used a shop vac to suck out from the discharge. May have to do several times. Note mine it the round type, insure that you get fan screw tight and put paint on it or the screw may back off and you'll be taking it to a radiator shop for a repair caused buy the fan blabes rubbind hole in the tubes.
