As a last gasp, don't wanna fix it measure, you might try some Bars-Leaks or equivalent. My recommendation is to go ahead and spend the time to have your heater core repaired or replaced as necessary, and you might even have your radiator checked as well, since you are making the mess and the trips. Take a look at all of your hoses,thermostat, heater control valve, and hose clamps while you are doing the deed. You'll be glad you did when it is 02:00 A.M. and coming back from a Thanksgiving tryptophan feast, eh?