ok before i go ripping out the dash to change the heater core i'l ask this to make sure its the problem..i have this white smoke that will come out when the car has been running a bit, and it condinsates on the windows and i have to wipe it off to see, cuz the defrost will just put out more of it..and it doesnt wipe off as easy as water would..its like a little oily?? kinda...could this be a crack in the core?