1996 Ford Mustang my radiator

Ok, so I cracked my radiator down by the bottom mount. Im getting a new radiator but dont have the money for it for like two weeks, I used some quicksteel and covered the entire crack all the way around it, it seems to be holding but my car is still overheating, im testing it using water so I dont waste money, my friend says theres just air in it but I dont know where the air bleed valve is? So thats question one..I dont know why its overheating still? Is it possibly just air? I just replaced both head gaskets. And got a new thermostat, and now my radiators messed up, and it doesnt make sense that its still overheating. It still drips out from the quick steel but nowhere near enough to overheat like this. Advice, answers, somethin?