if it is a small leak it is a very inexpensive fix and can be done from a couple of spices in your kitchen. either black pepper or cinnamon on small leaks . just pour a small box of either in the radiator. thye swell when wet and clog the hole and seal it up. if it is bigger the heater core is under the dash of it. the heater core should be behind the glove box of it . remove the hoses from the core under the hood. then remove the glove compartment and you should be looking right at the heater core. remove the duct work from it and then remove the bolts from it and pull it out. find the hole and solder it shut or replace it with a new one they are fairly cheap
duey
January 2012