So I'm driving my 2.8L 06 canyon and it overheats, AC off message, heater not working lots of dinging. Take it home, drain the brown sludge that had become my antifreeze, flush the radiator, heater core and block until it ran clear. I then changed the thermostat (180 deg, tested in boiling water works well), filled her up and burped the system. Now it's still running hot, top of the gauge, ac off alarms ringing hot. Heater still blowing cold. Wondering if anyone has had similar problems and would like to avoid replacing everything if there's an easy fix that I'm not thinking of. Thanks in advance for any advice.