check coolant level, fill it cause its probably low. look for bleeder screws on the thermostat housing or a radiator hose connection and loosen those till coolant comes out with no bubbles. squeeze the upper hose a few times to get all the air out. tighen screw and refill coolant. if that doesnt work its probably the thermostat again

 

FYI nuke, air bleeder screw is located next to the top radiator hose on the intake manifold. 10mm, dont drop it

 

i wont lie i dont know ya'lls type of cars very well but if it were my car acting like that. i would very first check the radiator cap. i know dumb right. but hang on. if the seal is cork and is rotting it can swell with moisture from the coolant going out to the overflow and not let it back in. when the car cycled it would greatly lower the fluid level available and warm the car up. then when you shut it off the cycling stopped and the contraction of the hose and the lack of pressure would be enough to let the water suck back from the overflow. It happened to me once. i went and bought a pump t-stat hoses and sensors for a bad cap.

 

i'll check, but its been running fine so far.

 

well it's been acting up again. mainly only if i'm sitting at idle. once i turn it off and start it again it runs fine. looks like i'm going to have to check it out some more.

 

try bleeding out the air again, if nothing comes out id suspect your t-stat.

 

damn i should have done this sooner. that's exactly what it was. the rubber seal had come off causing the coolant to leak into the overflow tank. when there was no air across the radiator it was heating up. when i turned it off the coolant went back in the radiator, and would seem to be fixed. i'm just glad i didn't go and get a bunch of stuff and pay someone to fix it when all it cost was $7.

 

This is long dead. But heck glad to help.