85 Mustang GT coolant issue help plz

[82olds98]

i have a mildly built 302 in my 85 GT. The problem is that every couple of days of driving my coolant will beging to push out into the overflow bottle and stay there. Due to this the car will begin to overheat and ive found that the only way to get the car to suck the coolant back into the radiator is to vent the cap until most of the pressure is off and then it will bring the coolant back into the radiator. If anyone has any idea of what is wrong id appreciate the help thanks

[driver540]

If you can get access to a pressure tester, I would check your radiator cap first. Spring may be getting weak and allowing coolant to blow by when system is pressurised