My cars been in the paint shop about all winter so I decided it needed a little excercise today. I drove about twenty miles and stopped about twenty minutes then drove another thiry and all was fine. I then stopped about an hour and a half. Then drove about thirty miles and had no heat. Blower worked fine if you count cold air. Water temp was normal. I then stopped for dinner for about another hour and a half (slooooow service) and when I headed home the heater was fine all the way (about fifty miles). I checked the water when I got home and the level is fine.
I was stumped when it quit working. Then when it started again I was totally stumped.
Any of you gurus out there have any idea what is going on?
Try filling your radiator this way. Take cap off and run engine until thermostat opens. Turn heater on hot. Have a helper idle the engine about 1200-1500rpm. You should see the coolant level drop. Fill it up and replace the cap before letting off the idle. Your cooling system will now be full. This assumes that your system isn't dirty or clogged. You may want to flush it first.
Passenger side next to the heater blower motor is a vacuum accuated valve. either the vacuum is not there, the diaphram is leaking or the valve is stuck. I usually have to move mine by hand after it has set for a while or I just tie it open with a ty-wrap.