This may sound odd, but if you're coolant reservoir is too full it will run a tad hotter then normal.

There are no breathers in the system so when the coolant gets real hot it causes a ton of pressure and if there isn't enough expansion room in the coolant tank it gets hot and gets hot fast too.

You can install an inline breather, reduce the coolant, or just get it real hot and then pull over and crack open the cap to let out the pressure and you're good to go.

I went through 3 thermos thinking they were stuck closed before I realised this odd little issue.