Hey first Tim on a forum every. Figured I’d give it a try. Anyways I have a 2001 5.9ln cummins. I just rebuilt the motor ground up bearing crank cam seals hole nine. The head was decked magna fluxed and rebuilt with valves and springs. So I got it fired up running and first 2 days everything was awsome. 3 day I noticed temp gauge was moving around. I have had 2 of theses truck and temp gauges never bounced back and forth. They would open drop a bit the. Hold solid just above 90.c. And my 2001 never bounced before the motor rebuild either. I have re torqued the head check all hoses for leaks, burped the system put my matco compression leak tester and I’m getting no exhaust gas into the rad coolant it not dropping. So I also changed the thermostat twice with a Cummins 190 and also changed the coolant temp sensor with a Cummins coolant temp sensor still nothing changed. I also pressurized the rad system with a rad tester and pressure bled off 4psi in a hour. Now I did the 3 times pressure bled off the last 3 times I checked pressure has not bled off holds a solid 16psi for hours. Truck is a 24v with a 47re. Now like I said I have had to trucks that gauge never bounced when driving it held one spot solid. And I don’t belive some of the stuff that says it’s normal it didn’t do it before what’s causing it now. Also changed rad cap. Any info is good Info. Please help losing sleep over this