a silly answer to your problem...i had the same problem and i couldnt believe it.
check your radiator caps.
i had that problem in 2 cars and believe it or not they were kinda new 2001 and 2002 rx7s

con

 

Yeah ichanged the main cuz it was getting build up on it, but i did not change the ast one it looks fine? but you never know i guess

 

Also , if any of U guys run stand alone computers , I have found that too much ignition advance at idle and low load and not enougn split also causes the coolant temps to rise.

 

Okay so I got that tool to bleed out the air in the cooling system, and man you there was alot of air so i am going to do it a couple times jst to make sure i get all of it.

Any how while i was doing this i noticed something interesting, when i get to 95- 98 C the fan does not come on wich i belive its supposed to? but yet if I shut the car off and leave it in accesories the fan comes on instant, which i thought was strange so i start the car back up and as soon as i start it the fan shuts off and don't come on even though the temp is still above 95 a little, so anyone have an idea on why this is happening? Thank you

 

^^ When the motor is off and no coolant is circulating, the hottest parts of the motor (the lower part of the housings, and the turbochargers) aren't receiving fresh coolant, so the coolant near them heats up. This is sometimes referred to as 'heat soak.' On a warm summer day, I've seen temps climb from 190F at shutoff to 220F after the car was only off for 5-10 minutes.


If you turn the ignition to ON without starting the motor, the stock ECU will notice the hot coolant temp and turn the fans on, but the fans are cooling the coolant inside the radiator, and that coolant isn't being circulated through the motor. When you turn the motor on, the fresh coolant passes by the sensor, and the fans will turn off very quickly (less than two seconds, depending on how long the engine has been off).

The actual turn-on temperature of the fans will vary depending on your ECU. If you're running the stock ECU and thermoswitch, your fans won't turn on until 220F (~105C) or so.

-s-

 

Okay cool that makes since thank you, Im thinking that i might just wire the fans to a switch also just to help when im idling.