my car smelt like antifreeze when i started her up this morning, so i pull over to find antifreeze poring out of a hole in the firewall. the hole is right above the pass. side header and is about 7/16's in diameter. i get back in my car to inspect and see my windshield is fogged up from the vents "car sticks like antifreeze by now" and i have some drips comming from the pass. side bottom vent. i think its a heater core but im not 100% sure. also, the car has had no heat coming from the dash vent for some time now, and the lower vent seems to stay on all the time. any ideas?, and if it is the heater core how big of a job is it to fix? thanks, Justin