sierrathewhitesierra

My 2016 Sierra 1500 5.3l does the exact same and my dads 2015 silverado 1500 6.2l does it less but it will doing when wheeling up hills and stuff. From my research it’s the stock thermostat opens slowly to reduce pressure in the cooling system to stop the radiator from cracking. It’s very annoying thinking about trying aftermarket thermostats