i have a 2001 cadlilac deville. idles fine. gets hot while driving and over heats and blows cold air out the vents while on HOT. I flushed the radiator several times, flushed the heater core, replaced radiator, thermostat, water pump. I burped it several times. last time I parked on a hill with the passenger side in the air to help get any air out. STILL ACTS THE SAME WAY AS DAY ONE !!! any ideas next?
Blown head gasket! Northstar engines are notorious for blowing head gaskets! Have the coolant tested for the presence of combustion gases. If you have combustion gases in the coolant you have a blown head gasket and it's not worth fixing! Hope that helps! Jim