Excuse me if this should appear twice. I entered this once and when I sent it, it showed me logged out, so I'm trying this again. I have an 08 Silverado Extended cab LTZ, 5.3L, auto and 4wd, with 22K miles on it. This week it's been very hot with temps in the high 90's to low 100's. Twice this week I have gone out and started the truck after not being used for a day and a few seconds after starting there is a loud pop and then a clattering sound on the passenger side of the engine. The A/C is working OK. At first I thought it might be a stuck starter or the starter trying to re-engage, but yesterday I remotely started it and was standing by the passenger door when it occured and it sounds like it's blowing off pressure. Anyone have an idea what this might be? I hate taking it into the garage with this little to go on.