Ok I have a 2012 6.7 that I've been having over heating issues. Truck already had dpf delete with h&s tuner. First time I had the egr deleted and a new thermostat put ran good for about 2 weeks then started having the same problem again. I was told I was loosing pressure which was most likely a head gasket being blown so broke down forked out the cash for new gaskets and studs. When they pulled the head off the gasket was perfectly fine and had no holes or cracks and head was perfect but had new gaskets put in anyways with arp 425 head studs. Ran good for about another 2 weeks no I'm having the issue again but this time it's sparatic. I can run for a while (40-50 miles) no problem then I'll shoot from 201 degrees straight up to 230-245 all the way back down to 185-195 in a matter of a minute or. I've been told it's the thermostat again or its the water pump this time but am getting sick of throwing money into it just to have the issue keep coming up.

 

I had a similar problem to this and it ended up being a thermostat. Had a parts store thermostat in it and it didnt open up as much as a cummins brand thermostat so the coolant flow was greatly decreased. Put a cummins thermostat in amd no problems since

 

I agree with Dustin. Generally if you have intermittent problems with Temp spike then returning back to normal indicates thermostat sticking. Water Pumps usually show a constant temp problem.