Given the combination of symptoms, the first thing would be to have a chemical test done at the reservoir to check for a leaking cylinder head gasket. That involves drawing air from the reservoir through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.
Combustion gases that sneak into the cooling system can pool under the thermostat and prevent it from opening. Thermostats have to be hit with hot liquid to open. The gases can also cause hot coolant to stop flowing through the heater core, and that would result in your cold air.
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Sunday, February 8th, 2015 AT 7:01 PM