I have a 96 gt and while I was letting air out of the cooling system about a week ago (car at operating temperature with heater on) I noticed that there was lots of coolant coming out of the evaporator case drain plug. I did some testing and this occurs both when the heat and a/c are on. Is my heater core broken? Is my evaporator case broken? How do I know which one to replace?

Thanks!

 

heater core most likely. verify the hoses arent leaking on the firewall side and into the case before removing the dash. its quite the job. The hvac case is supposed to allow water to drain from the evaporator when the AC is running (hence cars always having water puddles while sitting with ac on)