thermostat sticking?
 

84 S-Model 12A Nikki Carb, stripped emissions, GSL rear-end. Whenever I start up, my car will warm up then get a little too warm and then the temp will go back down to normal op temp. I think my thermostat is opening too late. Any other ideas of what would cause this?
Also, someone told me to put transmission oil in the engine through the spark plug holes. Is this a good suggestion?

when was the last time you change your coolant...?? i change my ever 6 months.....dump your coolant and replace with distilled water run it for like 3 miles dump replace with new coolant......good luck....:peace:

why would you put AT fluid in your engine if its running ok? Dump seafoam down the carb if you want to de carbon it, but dont use AT fluid. you could boil your thermostat to see if it is opening when it should, use a thermometer and it should open at (not 100% sure on these, but maybe 180*?) then close shortly after removing it from the boiling water. If its not a mazda brand thermostat then I'd suggest tossing yours and buying a factory mazda one with a jiggle pin.

thermostat might be on its way out, i'd replace it, they are like $16...

More like $22 for the good kind.