Possible contributors to your problem are
Thermostat sticking => 更換便宜
Water pump weak (impellars eroded) => 不知車況,裏程,維修記錄等,存在可能,如需要更換正時帶,建議一起更換。
Collapsed hose inner layer restricting flow =〉不知車況,裏程等,自查, 更換便宜
Bad radiator cap preventing the coolant in the engine from being able to pressurize to increase boiling point. =〉更換便宜