My xbox is still freezing after installing the rrod repair kit

ever since i had my xbox it has had the red ring of death, i tried to fix it before but i forgot the clean the existing thermal paste. After that i took it apart again and cleaned everything off of it, then i ordered and installed the repair kit. The xbox was working for about a day or two and then it froze, i turned it back on and it was working fine then after about ten minutes it freezes again. I shut it off and turned it back on and i got the rrod again. Is it because of me trying to clean it the first time? Or did i need to re flow it? If you can help please tell me and the model for the xbox is a xenon