I bought a new Pi 3. I was trying to make a LFR (line following robot). When I powered l239D IC with 14 volts, the Pi suddenly got off and restarted. It gave me the temperature of about 124 degrees celsius after restarting. Then it went off again and never got on again. My OS is Raspbian. Can you tell me where would have I possibly gone wrong?
You mean I293D, right? Sounds like a mismatch in power-supply. I agree with the guys in the comments, you are probably connecting a too high voltage to the Pi.
According to this datasheet, you should work with pin 16 instead of pin 8.
I can also recommend you to connect the GND from the IC to the GND of the Pi, when you have more than one power supply. But I don't know if that's the case with you.