Thanks for your reply and insight. I have heard about the head warpage issue and this could be the problem, but from what I can see, I would think there has to be something else. Let me give you a few more details that I forgot to include in the first email.
Up until today, the truck has never really overheated(moved to the right, but stayed in normal range). Twice today I, shut the truck down when it passed the normal range and approached the red. I let it cool for about 30 minutes, then drove on.
The truck burns no oil, never has. I have checked the oil for coolant and there isn't any.
There is no oil in the coolant.
For the pastcouple of months, before the overheating issue began, when I would park the truck at night, I would hear the radiator rumble slightly as I walked in front of the truck. I have seen a trace of coolant present around the cap area during this time.
From, I assume the overheating pressure, the reservoir tank on top of the radiator has developed a pinhole leak that the coolant bubbles out of.
I believe that this is a seperate issue, but over the summer the AC/heater developed an issue where the fan motor works only on high speed. On AC, the driver vents blow cold, and the passenger vents blow warm/ambient. Conversely, with the heater on, the passenger vents blow warm(not hot), and the driver vents blow cold/ambient. This may be an unrelated issue that involves...the actuator on the vent gate?
Anyways, when I wrote, I was at Autozone trying to figure it out w/ a few of the guys there. As we ruled out the possibilities, we came down to maybe it is the radiator that is clogged and not allowing the coolant to flow. In your expert opinion, could it be the radiator? This vehicle has a history of radiators going out at sub 100k mileage. If so would a flushing be worth a try, or just replace it? Let me know your thoughts and I appreciate your knowledge and help.
PS- funny thing, when I left Autozone to go home, about 3 miles, the gauge went to the middle after about 1 mile. It did not go past there or get hot the rest of the way home. I let it run in the driveway for about 3-4 minutes, thinking surely it would begin to get hot, but it didn't.