On Saturday, I noticed a new noise from the area of the idler pulley. Not quite like a bearing going bad, but similar. It got a little worse on Sunday, but was noticeably gone when I left work Tuesday afternoon. Good... I thought.
Driving home from work and stuck in traffic, the temp guage began rising and hit the max. The DIC showed the temp icon and read "Engine Overheated - Idle Engine". I quickly pulled over and stopped the engine. No smoke or steam. Checked under hood for leaks, nothing. Let it cool then checked the resevoir for coolant. I saw there was some in the bottom and figured it was okay. Engine oil was low. Read the owner's manual and found there is a category for overheated engines with no steam!
After 20 minutes, I started it up. Temp was fine. Took off and got about 5 miles before the same thing happened. Repeat all the way home.
BTW, I turned the heater on full hot but only cool air came out. No heat. Engine compartment was not overly hot like some I have felt that overheated. And it seemed to cool down pretty quickly.
Today, my GM engineering friend tells me some of the chains used to drive the water pump are breaking. If that is what happened, it should be covered under warranty. Guess I'll find out because the dealer is coming to pick it up and check it out. I'll post the outcome.