I'm trying to diagnose a slow coolant leak and the service department can't find it. We get the occasional weak whiff of coolant in the cab and the reservoir is slowly being drawn down. Every couple hundred miles=1/2" of coolant loss. There is no noticeable leak and the service department pressurized the system with no obvious leaks.
I have the digital gauges and my coolant temp bounces around quite a bit. Usually it's pegged at 210 degrees but will bounce back and forth between 190-210 at times. Does your Duramax temp vary or does it stay constant at 210? All of my previous Duramax's held steady after they reached operating temp. I'm wondering if I have a thermostat problem and they're unwilling to change it without definitive proof.
Thanks!
-2018 GMC Sierra Denali 2500HD
