Heater blows cold air replaced heater core and thermostat
And flushed radiator and still cold
Don't know what else to do
Sounds like the blend door is not working. This door opens and closes between the evaporator and the heater core when there is a call for heat or cooling.
Start by checking all your vacumn lines up under the dash board, and also check all the blend door diapharms that the vacumn lines connect to, using a hand held vacumn pump to see if they are operational or have pin holes in the diaphrams causing an air leak so the doors do not operate properly.
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