2008 Tundra 5.7 temp issue.

Wow!!! It was the cap the whole time. Put all new coolant in it, new cap everything appears to be fine.

 

Hey guys, I have had this exact same problem for over a year and could not find a solution. Everyone I talk to could not understand why the engine would be hotter on cool mornings and normal in the afternoon. Thank you for posting your findings here. The broken piece was stuck in the little tube. We are running normal temps now.
Also, I got a cap that does not have the piece that breaks off. It still seals and relieves pressure so may be a better option.
Does anyone know the difference?

 

I had this problem for 9 months now. What a headache. I’m so glad I signed on here. I just found it as well.