Every phone I have owned so far has ended up with hardware issues and has been replaced under warranty and is the very reason I no longer root phones.
I use gsam battery monitor to check my temperature https://play.google.com/store/apps/d...m.gsamlabs.bbm just drag down the Notification bar and there you go.
If your phone ever reaches 140°F its ruined. This is the temperature when solder that holds your electronic components to the circuit board is compromised. If my phone ever reaches 105°F I just put it in refrigerated air for a few minutes. The A/C in your car or a refrigerator for 2 minutes
will work fine.