I'd buy an all brass one. I've never seen anything work on old dirty
plastic. Sealer from inside might / might not / might clog up ???
To expand the crack to clean it will only aggravate problem,
if you must try a fix, Weller makes a " Plastics tip " for the 8200
model gun, a repairman's favorite. You could try to melt in some milk
bottle plastic, A La Ski bottom repair candle.
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