I have had no problems with my heat until yeasteday it just stapped making hot air. the fan blows at all levels, but i only get lukewarm air at the highest heat level, if I turn it down at all it gets real cold.

from reading here, I think it might be the heater blend door, but would like someone to confirm that.

also, last week, I lost 3/4 gallon of coolant. when i pulled over to see where the leak was, it seemed to be at the top of the rad, behind the fan shroud. after letting it cool down I added coolant, and haven't had a problem since, I figured it was like a high pressure valve type thing.