Cooling problem

[m3nace]

I have a cooling issue was wondering if anyone could help diagnose it

My car overheats alot so I replaced the old leaky radiator with a mishimoto radiator with hoses too thinking it would stop overheating but now when I first start up and drive it overheats and after awhile it goes down. So I thought it was the thermostat not opening but a couple days ago I overheated, pulled over and poured more coolant in and now it hasnt overheated so now I think the thermostat is fine but the coolant is dissappearing wayy too fast and I have to pour coolant weekly for the motor to stay cool. Theres no coolant in the oil nor is there oil in the coolant or is there white smoke emittinh from the exhaust while I drive so idk what it is.. could it be the thermostat still? My knowledge is limited

[USAF EP3]

Pressure test the system to see if you're leaking coolant anywhere. You could have a leak that is evaporating before it actually leaks and makes a mess. I had this problem with my RX7 and it ending up being an old worn out hose that connected to the throttle body, never saw the coolant cause it would evaporate when it touched the engine. Do a google search for import radiator pressure testers.

[m3nace]

Ill be sure to check that out thanks usaf

[m3nace]

I hope its not the radiator so I dont have to get another one -.-

[m3nace]

Took it to a shop they diagnosed it as because I didnt run a coolant reservoir my cap couldnt hold all the coolant in and it was leaking through the reservoir tip which is why it was good when I poured coolant but after a week itd be all gone hope this helps the people with their problems in the future.. weird how it didnt happen with my b series motors