I went to Firestone today, 4/22. They replaced the belt, because their price is significantly lower, $83 out-the-door including shop fees, taxes, and anything else they could tack on. For no cost, they also rotated/balanced the tires (which I previously bought from them) and aligned it under their lifetime alignment agreement. I did need to go to Firestone - the HHR was out of alignment.

On to the dealer on Monday 4/23 for spark plugs and noise repair. It does sound like an exhaust noise to me. I may put off coolant exchange in case Firestone sends me another present. After all, there's no special need for the dealer to use its exchange machine vs Firestone's, assuming they both use Dexcool.

 

if it is a flexpipe, here is my how to(non turbo)....very simple if you got someone to weld for you.
https://www.chevyhhr.net/forums/how-tutorial-library-21/how-repair-flex-pipe-31536/

 

Tip for pinpointing exhaust leak - cover the tip of the exhaust pipe with your hand (pad with rag if too hot for you) - it will force more exhaust out of the source of the leak making it easier to find.

 

X 2

If it is the Flex pipe, that should be covered under the Emissions warranty..

 

Buzzing sound - is gasket the exhaust system, with high probability.
You replaced the belt, it was good. But the belt is not buzzing. Slack belt - whistle on a high note.

 

If it's the flex pipe, it would be covered for 8 years (I'm fine) or 80,000 miles (I'm at 95K) WHICHEVER COMES FIRST. How much should I expect to pay a dealer to weld in a new one?

 

Don't take this the wrong way, but getting a dealer to do this will probably cost 2-3x what a local muffler shop would charge.

 

I would go to a muffler shop first if I knew it was an exhaust problem, but I have my doubts. I really don't know where the noise is coming from. The weird thing is that it will not make the noise unless the vehicle is moving. That's why I wonder if it might be yet another hub bearing failure. When parked, I can rev it to 6000 RPM and nothing happens.

 

I had to replace my flex pipe last year - due to high-mileage too, I used an aftermarket one and the cost worked out to ~$340 (in USA would be much cheaper I am sure), including the installation at a local muffler shop. It included the cat as well - I was a little nervous that it might throw a code but it worked out ok. The weld-on flex end wasn't available here in Vancouver at the time, or I would have gone that route. Best of luck - keep us posted. I kinda regret not keeping the old pipe/cat and getting a weld-on flex end for it as a spare, but I have too many "spare" things hanging around already.

 

Oh, there should be enough room at the back of the engine compartment to visually check most of the the flex pipe for cracks and to feel around for an air leak being careful not to burn your fingers. At least that is how I checked mine and found the source of the leak.