drove wife's 08 silverado today, it complained about being hot and told me it would not let me use the AC. I looked at the temp gage, said cold. I felt the hoses, looked at coolant level, all seems normal. I'm guessing the computer is not getting good temp sensor data...so I figured I'd throw a part at it. I went to drain the coolant a bit, there's no drain plug! there's a place for it, but the hole is not drilled or threaded.