I have an 06 5.9 auto. Every morning that its cold I start my truck and let it run for about 15 minutes with defrost on full blast, heat on full blast. That way when I run carpool my three kids aren't so cold.

This morning the outside temp was 27 degrees. Did my normal routine, but when I went out to get in the truck it was like I had never turned the heat on. As I started to drive, the temp gauge started rising, but still no heat. After about 4 miles the temp gauge shot up to the red, and my check gauges light came on. Then the temp gauge went down to normal and the heat finally kicked in.

Anybody have a clue what is going on? Thanks in advance for any help.

 

Sounds like it has air in the cooling system, did you check your coolant level?
If it is or was low, sometimes you have to run it with the cap loose until the thermostat opens so it can burp all the air out.

 

Sounds like you loss coolant possible water pump leaking. Do not remove radiator cap untill engine cools down then very slowy remove cap allowing any pressure to escape before removing cap then add coolant. Have cooling system checked for leaks.