rb20 boiling over but not over heating
 

So far ive changed my thermostat and flush the radiator 5 or 6 times. Car runs fine then boils out of the overflow tank. My oil looks normal coolant had turned red at one point but not since flushing. Blown head gaskest maybe? Im out of ideas

take the radiator cap off and start car cold if water shoots out could be a blown H/G or bad waterpump.

buy a pressure tester and hold the system at 15PSI dont go more then this because you might break something, let it sit for an hour, if it drops pressure you have a internal leak somewhere.

compression test your engine. when was the last time you replaced the water pump? how old are the radiator hoses?

did you BURP the system? is your coolant temp sensor (gauge) reading properly?

Ive started the car with cap off and no coolant shot out. I replaced the water pump last year. My stock res has a vent in the top. If I run pressure test would it not just come out the vent? My next step was going to replace both temp sensors but now im not sure

are you using the stock mechanical fan with shroud or e fans?

Some efans im not sure what kind.

how does the rubber seal on the rad cap look?

the pressure test would not leak because it's designed to not leak, the stock cap is designed to relieve pressure after 13psi or 16psi depending on cap.

compression/leak down/ pressure test is in order i believe.

Well I took a look today and the color has changed again to rusty red. Wich leads me to believe it is indeed a corroded water pump.