I don't think it's leaking, you would smell it, as Mr. S says. I read your original post early this morning and I used my last 5 minutes before work to look up heater core access in the factory books. It didn't say much! You go under the dash on the passenger side, and there are apparently 5 screws, and there it is. The book refers to a special tool to disconnect the core lines. I hate it when they say that.