found a TSB, PI1513F, found it here, from a post a while ago using google.
i found my issue by a low reservoir, well lower than it should be, noticed when i was doing my intake.
i marked it, and kept an eye on it.
warranty was going up in 60 days.
checked it 4 weeks after my mark, was 1/2" lower.
flashlight, found it. driver side top corner.
researched, found the TSB luckly, powertrain up in 30 days now.
called local dealer, took me right in, replaced tstat housing and radiator under warranty.
check your trucks guys.
1500, silverado, 2016, 5.3, 34k miles.