1993 Taurus Wagon - Heater problem

My heater has started acting up. Blows hot air then cold while selector is on full HOT setting? Checked rad levels - did add 1/2 liter of antifreeze to top it off.
No change. I know they work on a vacuum system. What should I be checking?
Thanks, Eric
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ecm opined in

Sequence matters a lot... take a while to get hot, then after it does.. get cold again? Hear gurgling in heater area?
could be air bubble in core
Make sure that the block is purged of air and that the hose from the thermostat area goes to BOTTOM heater core nipple and the hose from pump goes to top.
--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

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ecm wrote:

Do you have a 3.8? Loosing any antifreeze? Smell any sweet smells? white exhaust vapor?
Bob
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You're thinking the same thing I am. The first symptoms of the famous 3.8 head gasket leak. Bob
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What engine do you have? Bob

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