I have a 05 lly and I just replaced the head gaskets and when I was doing it both heads were resurfaced, valve job, new thermostats and radiator cap and I flushed the system. The radiator hose will kind of suck shut but then it will go right back to normal after a few minutes and it's not hard. It's not overheating it's running at its normal temp. Also have a egr delete. I got to work this morning let the truck sit for about 10 minutes and took of the radiator cap and there was no pressure. Anyone have any other ideas?