So there was no heat in my 94 xr7 v8. First I replaced the thermostat. That didn't work. Just got her back together after putting a new heater core. The old heater core was packed full of whatever they put in blue devil. still no heat...I didn't drain the old coolant, do you think that where I went wrong? I'm feeling pretty foolish for not replacing all of the radiator fluid. Or maybe I installed the thermostat wrong, anyways I'm at a lost.