420A Overflow tank pressure

[Eclispe Rs]

I swapped from a OEM radiator and fans and shrouds to a mishimoto radiator and fans and shrouds and mishimoto stainless steel radiator flexible hoses. I swapped connector to fans but they won’t turn on. I took out A/C compressor and all but why is pressure being built?

Is it type of coolant I’m using?

And I also replaced thermostat and housing and sensor and sender

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[BLACK'98DSM]

Pressure in the reservoir is usually a headgasket issue or running hot. If it isn't running hot, I'd get some combustion leak fluid and check.

 

[CKOPOCT]

Stainless steel hoses resting against the exhaust header and down pipe? I'ma thinkin' maybe some insulating wrap around the exhaust might help keep the coolant from flash boiling at those hot spots. That, or go back to stock radiator and hoses.