The noise only happens on cold start AND cold weather. I'm in northern virginia. If it's 38 or above, I may not hear it. Sound lasts only for about 2 to 3 seconds. It sounds like it's coming from the rear middle of engine compartment. It sounds like something opening or closing. The physical sound is like a noisy idler bearing, or belt type noise. It's right at start-up, cold, thats why i think it's something opening. Thanks guys.