water temp sensor question

[quinteros05]

So my check engine light has been on since i got my car, i always thought it was O2 sensor so i change it and no change. A couple of days ago i take it to my friends shop and he pops the computer on it and it reads Code 13. Apparently the water temp sensor is bad so i go to Autozone and buy the 2 sensors. I put them on and the light stays off for about two hours before it lights back up, any ideas on what is going on??