Hello

Hello i was wondering if anybody would know whats wrong with my 2003 volvo. I have cummins isx 475hp engine and im having problems with coolant temperature. I notice that while im driving my water temperature gauge is jumping back and forth from 175 to 190. While idling the temperature sometimes goes up to 215. I also noticed that my coolant expansion tank is full with coolant and from time to time i need to add coolant to my coolant tank. I change the thermostat and coolant temperature sensor but still the same thing is happening. Thank you for the help

 

I didnt check for air yet but there is no exhaust gas or oil in the cooling system

 

I checked but no air is in the cooling system