TL;DR 2014 covered eventually
I'm a second owner of an early model 2014 Silverado with 32k mi. and 5 year/100k mi warranty will be over in August. Took it to local dealership and asked them to look at this issue and some bearing failure noise about 2 weeks ago. They couldn't see anything leaking from the radiator or coolant system as to why I would see steam. They also couldn't get the bearing noise to repeat so I left with advice to keep an eye out (more appropriately a nose out). Got the bearing noise again and this time I got it on a video and sent it to my service adviser. He showed it to a tech and they agreed that it was worth leaving with them to find out which bearing it was. Turned out, after a few days, and me allowing the tech to take my truck home with him, that it was the water pump bearing going bad. While the tech was underneath the truck he noticed that there was, in fact, leaking from the lower left corner of the radiator. The SA called me yesterday to let me know about both problems and that the WP was covered under power train warranty and that the radiator would cost me under $1k. I gave the ok to perform the WP replacement but that I would think about the radiator since the reservoir wasn't losing noticeable amounts of coolant (I would get to it later when the weather was warmer). Last night I spent about 30 seconds searching the internet for how to replace this radiator and found the 15829 special coverage notice and this forum topic. Called the SA the this (next) morning and told him about what I had found and within 10 minutes I get a call back to say that the radiator is covered at no cost to me and all work to be done today (that same day). My SA gave me some story about that this must be a relatively new special coverage and that's why he didn't know about it when I asked him. He even doubled down on the excuse when I told him that this notice was dated back to Nov of 2016. Hopefully it was just an honest mistake but it seems unlikely that he or someone else wouldn't have dealt with this issue before. Any way, thanks to this forum and all of its members in sharing their stories and helping us all out. Had it not been for this forum, I would have not known to pursue the dealership to fix at no cost, as I would never get the letter from GM like the original owner must have. Good thing is that I did get a loaner for the week of troubleshooting and repair.