i dont know if this is the right place to post but i need some guidance. my car is overheating badly. but its kinda weird. at first i thought i had air in the system so i turn on the hot air and no heat. so i added more coolant and after a few revs temp went down. i replaced the cap and car was fine for like a few weeks. now its overheating again. but as soon as i turn on the hot air. engine temp goes back to normal. in addition to that im getting boiling in the reservoir. sooo i added more coolant and same rad cap. could it be that my new cap is bad, i did get it at autozone??? i check all around the system for leaks and i didnt see any. only the coolant that was burp out when boiling. help me out im out of ideas. thanks