NEED HELP OVERHEATING

hi how's it going everyone well here's the story my girlfriend just brought a 01 mustang and it was overheating so i replaced the t-stat and water pump.it stop overheating for 3-4 months,then one day coolant shot out the reservoir so i thought the radiator was bad and replaced it and so after replacing it we took it for a 30 mins drive.it was find until we was on our way back to her house and then it started to run hot.so i took the t-stat out and put it in boiling water and it opened so i put it back on and took it for another test drive then atfer 30 mins later it ran hot again.so i check on the upper and lower radiator hose and they both was hot.so any ideas would help thanks

there's no water in the oil nor oil in the radiator next time i go over there im pressure tested the car and i bleed the coolant system when i install the radiator but didnt do it when i put the t-stat back on i guess i need to rebleed it then thx for the advice i'll update when i do it


first time i bleed the air out the system is when i change the radiator by taking the 15mm screw off and bubbles and and coolant was shooting out,i did it for 30 mins