Stock radiators are notorious for having cracks on the top of the tank...it's plastic. It happened to mine. It didn't produce symptoms as bad as yours, but maybe your crack is worse...or there's a hole in your radiator.
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2015 Ford Mustang GT Fastback - Ingot Silver - 6M - Performance Package - Gibson Catback, JLT CAI, FR 47lb injectors, BAMA E85 tune, Eibach Sportline, BMR wheel hop kit, UPR oil separator, Steeda shifter bushing/bracket
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