ok it overheated the other day. i got home replaced all the coolant, took out the thermostat got a new set of belts on it and checked for leaks. none found. the temp gauge shows the temp at normal (little above 1/4) and then all the sudden the revs seem to go up to about 1.2-1.5k and the temp gauge shows about 3/4 up the bar. then itll stay there for anywhere between 2 seconds to 2 min. then the temp will drop down to about normal. and this will repeat randomly. the seals look good on the coolant caps. i smoke blus smoke on start up everytime, i have 163k miles on teh original motor. there is no coolant in the oil, or vise versa. any advice or knowledge on the subject would be appreciated!!!! thanks in advance

 

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Your may have an air pocket in the coolant.

When you filled it did you remove the bleeder screw and fill it till coolant is streaming out the hole? then plug it and fill it until its full. Let it settle and top it off?

 

The stock gauge should never "shoot up." It sounds to me like you need an aftermarket gauge to double check. You can get one from O'Reilly's for about 30-35 bucks (iEquus is the brand.) I just did a writeup on how to mount the sensor using stuff from home depot. https://www.rx7club.com/showthread.p...ghlight=sensor