hey guys looking for a little help with an overheating issue. I noticed on my scangauge recently that my temps have been spiking. I used to be running below 200* all the time even up steep climbs on the highway (live in Summit County, CO). Now I am getting temps 205-210* just driving around town. I also just very recently noticed that when I turn the truck off after its been that hot that the coolant is boiling into the overflow. I found that if I let the truck idle when I stop it cools its self down below 200* and it will not boil and i see no issues. As the truck cools back down all the coolant is sucked back into the system. I have been driving it like this for a month now (4 mile communte a day) and I haven't lost a drop of coolant, and I have no mixing with the oil. The forum got me crazed that my HG went but I went and got a combustion leak test kit and after the truck running for 15-20min I showed absolutely no sign of combustion gas in the rad. I also did the fan clutch shortly after the issue showed up with slight improvement.
I guess im looking for my next step, thermostat?, water pump?, common air leaks in this system? what may be causing this issue.