I still haven't figured mine out on the. 2015 2500 5.7 hemi. When you first start it up in the morning, it will run cold for 15 minutes then gradually go away to warm. This happens EVERY time! Once warm it will not get cold again until the next morning after sitting all night. My dealer techs couldn't figure it out, did the dye thing, charged it twice, and now it is in the shop until they figure it out...