So this is turning into a bigger project than I thought. I've put about 1500 miles on the truck so far and I'm thinking I may have a HG issue. Sometimes after it has cooled off, I can open the overflow and it will blow bubbles.... While idling, I open it up and watch for bubbles, but never have any. The overflow isn't pissing fluid and the upper radiator hose isn't hard. Today I pulled around our 850 gallon fuel trailer 20+ miles, so I thought for sure it would have more symptoms of a bad HG from having sustained boost, but not so much as a bubble in the system. Why do I keep getting random bubbles? My other duramax doesn't do this. I did have the injectors changed before I started driving it, but usually you can get all the bubbles out after 25 miles or so. Any ideas?