I've been having an intermittent "running warm" condition for a few weeks too that I think I finally figured out today. I've also been smelling antifreeze really faintly too, but could not for the life of me figure out where it was coming from.

I changed the pressure cap and the tstat which were both needed and both helped, but every once in a while it would still shoot up to the point where I was worried...

Well today when I got home I finally saw some steam coming from the radiator and found a spot where some antifreeze was bubbling out pretty good. Verdict: cracked radiator. I think what it was doing is every once in a while it would let in a bubble that would take a while to work out. I'd run hot until it flushed itself out and then it would be fine.

I went ahead and changed the radiator to a new one and did the water pump while I was in there as I have no idea how long it's been on there.

I think it's fixed but of course I won't know for sure until tomorrow.

Make sure you turn your heat ON, to circulate the air out of the core, and you should be fine.

My problem is defintely fixed. The temp gauge needle hasn't been this steady since the truck was new.

The afternoon ride with the heat index at 110 this afternoon will be the final answer, but it looked really good this morning.