ISX 15 Puking Coolant From Reservoir

Hello, I have an issue with my 2011 Volvo with the ISX 15 cummins, when I am driving the truck my temperature stays arount 170 to 180 degrees, but when I stop the truck and turn the engine off, I can turn the key to the on position and watch the temperature climb from 180 degrees to 210 some times 230 degrees in a matter of 3-4 minutes and when I open the hood the upper radiator hose is pulsating and the coolant appears to be boiling causing it to come out of my overflow hose on the coolant reservoir, I have had the reservoir, cap and thermostat replaced to correct this issue but no success, Volvo of Denver could not locate the issue and I am not sure what else to do. I don't have any ECM codes, no smoke, don't lose any coolant unless I shut the engine off, and no external leaks. Please Help, truck has about 745K on it. Thanks

 

Can you explain the bad cap situation a little more? When the reservoir was replaced it came with a new cap and low coolant sensor, the rubber underneath the cap looks pretty good and I don't see anything leaking from it, is there a way to test the cap? Also when I have a completely cold engine the coolant level is about a half of an inch below the LOW COLD mark, so when I top it off to just under the Filled Line, and let it just idle until it reaches temp all the coolant will stay in and the next time I shut the truck off and let it cool the coolant is still where I topped it off at, but if I drive it, come to a stop, park and shut truck off, once that temp rises it pukes it out of the overflow then it will be back to the LOW COLD mark, to me it reminds me of when a car has trapped air in the system but I have no clue of how to get it out if that's the case, oil samples show no signs of coolant, and literally if I keep this truck running and never shut it off I wouldn't have any issues

 

If I idle the truck its usually around 170 degrees, but after I drive the truck and come to a park its around 180 - 185 degrees, if I let it idle after coming to a park the temp will not go back down to 170 degrees unless I am moving, 10-15 mins goes by idling but temp will stay around 180-185, it is when the temp is in that area that if I shut the truck off and check the temp with my Infrared thermometer pointed to the upper hose housing I can see a temp increase to around 212 degrees matching the gauge on the odometer and the engine is off, once temp gets that high the upper hose starts shaking and I see coolant boiling in the reservoir then it comes out of the overflow, it's raised as high as 231 degrees with the engine off, no one can seem to figure this out, radiator, reservoir, cap, coolant temp sensor on head, and thermostat have been replaced.

 

Oil shows no signs of Coolant, oil pressure is 26 psi at warm idle and 32-38 psi going down the road