2016 cuminns isx15 over pressure in overflow

[702autotech]

It was asked if it was de-mandated no it is all original how it came from factory. I did find the little hose from radiator to top of reservoir was cracking when squeezed so I replaced it, I also noticed that when I pressurized the system the coolant dropped about an inch or so until I release the pressure then its back normal and when its hot the upper radiator pipe is hot as the lower one from the radiator is cold except where it attaches to the engine.