ok so we picked up this smooth running fc for 950 bucks and its in GREAT cosmetic shape. guy swapped the radiator with a race aluminum radiator and it started overheating. we change the thermostat, thermostat cap, water pump, coolant temperature sensor, coolant flush, and still giving us issues. i dont think its the coolant seal, no funny coolant pressure or discoloration. the reservoir boils over, and overheats at idle. still overheats at highway speeds, but slowly, and temperature is extremely sporadic. we got all the air out of the lines also. someone please help, this car is in too good of condition for something like this to happen.

 

Have you checked the water pump?

What kind of fan setup is used?

Can you post a few pictures of the engine bay?

 

When the reservior boils over, are you sure that it isn't due to exhaust gases entering the cooling system? This seems to be the most common failure on FCs once they start overheating.



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Have you tried the champagne bubble test to verify that all air is out of the system? Also when you run this test you'll be able to verify if the coolant seals have failed or not.

 

Coming from similiar experience it sounds like coolant seals are bad or going bad. Best thing to due is like me and tear it down and fix it before it kills the motor.

 

This is what you'll need for the champagne bubble test:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/radiator-cap-funnel-eliminate-air-bubbles-342309/

 

Champagne bubble test. I like that. I've always called it "the end" test. Cause when you see them. That's the end of your engine.