the crystals will be visible with the naked eye and they'll be white in color. The gasket is teh most probable cause, a cracked head could do the same though.

To check the fan clutch, put a short piece of string on the fan then start the motor. If you can hold the fan from turningwith a firm grip, the fan clutch is bad. if it pulls the string out of your hand, it's good.

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Thanks, Nels
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86 300E
93 W250 4X4 Cummins Power
72 F250 Highboy
89 S-10 408ci BBC
custom V Four Chopper
77 Peterbilt 352
83 Jeep CJ-5