2001 Ford Windstar No heat in

Feel the two heater hoses after the engine is warmed up. They should be too hot to hold onto for very long. If they're cool, feel the upper radiator hose. If it is cool, and the engine appears to be running too hot, you might suspect a leaking cylinder head gasket. That will allow combustion gases to sneak into the cooling system where it can pool under the thermostat. Thermostats have to be hit with hot liquid to open. Hot air won't do it.

If that looks like what's happening, there's a chemical test your mechanic can do to verify it. That involves drawing air from the radiator 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.