If its cool enough to open the radiator cap, maybe check the fluid. If it looks off color or smells burned, flush might be a good step to getting you home. Also, Koyo outsourced to China/Indonesia some years back (only the racing aluminum are designed/manufactured in Japan now), and while some...
Im going to add that even parking the truck on a sloped driveway/street with the engine on the high side will help be sure you have all of the air out.
Could be a few things, first thought is your t-stat is acting up or not opening consistently (may be installed upside down or out of the 15deg...