Coolant issue

[Evilevo8]

Well here's the basics on the car:

Fully built 2.0L motor
GT37R turbo
slim line radiator fan
factory radiator
factory thermostat
104K miles on the chassis

Last week car was running normal as I sat at work waiting for the Mrs. and no A/C running.. after about 10 minutes decided to kick the A/C on... after a minute or 2 notices AC not as cold as normal.. looked at temp sensor.. 3/4 way up.. FAWK!!
Coolant was boiling in the overflow bottle and out the tube... let it cool down looked over everything(carefully) let the rad fan run with key in on position but not running obviously. Drove home.. checked.. had a friend come over with a younger thermostat 40K miles Swapped out.. checked it no issue(coolant was added) ran car idle for awhile then A/C on... no issue.. got on it 20psi(low setting) no issue no white smoke. Figured just sticky thermostat since had alittle corrosion on it.
Fast forward to yesterday. Sitting waiting to pull into traffic car started climbing with AC off... SH!T! turned car off for a second..turned on.. and everything fine fan running no issue. Got home let it cool checked nothing in the overflow other than alittle coolant.
My theory is this:
Radiator fan relay possibly going bad intermittently? Was thinking about replacing it and the coolant temp sensor since both are 104K miles on them. Any other ideas? I thought headgasket since its got 60K miles on the built motor, but no white smoke no bubbles in coolant...

[DerekEVO]

my car does the same thing. its a bad fan control module. those things had recalls on the early evo's. you should have you vin checked. i have an aem and i am going to replace the fan module with a simple relay. i guess if you have stock ecu a new fan control module would be in order. next time it runs hot pop the hood and see if both your fans are running. hope this helps.

[Evilevo8]

Helps alot. I had my VIN checked at the dealer but it didn't come back... module is 108.05 my cost. I have an AEM as well. someone mentioned doing a simple switch relay and running it at all times which shouldn't be a problem even though tis a daily. I might just swap the module and let the AEM just control it though...

[projectxmatt]

My DSM did this at one point, what ended up being wrong was i had a few air bubbles in the coolant system. It ran fine most of the time while i was moving and a lot of times while i was idling, but every once in awhile it would start to climb. Bled the coolant system never had the issue again.

[Evilevo8]

My DSM did this at one point, what ended up being wrong was i had a few air bubbles in the coolant system. It ran fine most of the time while i was moving and a lot of times while i was idling, but every once in awhile it would start to climb. Bled the coolant system never had the issue again.

Ya buddy said I should pressure test it..might have slight pinhole leak allowing air in as well.. weekend project here I come Haha