Have you rechecked to make sure the coolant is full in the radiator? When you replaced the thermostat, did you replace the entire thermostat housing/thermostat as a unit?
Do this. If the coolant is full, start the engine, turn on the heater, allow the engine to reach operating temperature, and turn off the engine.
Feel both heater core hoses at the firewall. Both should be hot. Let me know if that is the case.
Let me know what you find.
Thursday, December 15th, 2022 AT 9:02 PM