this happened to me too .if its the same problem there is a electric vavle that opens and closes to let coolent into the heater core its controlled by your cold hot switch on your console any way if this does not open and close you cant anything to your heater core. its on the end of the heater core and is apart of heater core itself cant miss it .i would check to see if you are getting power to it first before you go tearing out the heater core not a fun job .good luck.ps its on the drivers side of the heater core and its attached to hoses coming thru the fire wall .