Okay

With key off, brake pedal still goes to the floor

I then pump the pedal and still holding it, start the car. Pedal goes to floor

After running a minute or 2, I shut car off. Then remove vacuum hose. There is no air hissing. BUT, I tried to remove the check valve to inspect it and as I try to wiggle it free from the booster, air rushes in

From what I am gathering here, I have a bad master cylinder, the booster seems ok.

Thoughts?

 

Yes, but inspect the wheel cylinders and calipers and hoses/lines to be sure.

 

And check between the master and the booster for brake fluid

 

I would agree. Master cylinder is the problem.
" then pump the pedal and still holding it, start the car. Pedal goes to floor"
That tells me the booster is OK.

 

Yes Cat Man, I agree with you. I have a new AC Delco one on order, it shall be here Wednesday. Thank you for your help, and this goes for everyone who contributed. I will update this thread once the rep[air has been done

 

I've seen a lot of masters leak from there.
The flange that bolts to the booster would have a relief cut so when it did leak you could see it.
From pictures I've found there is none on the HHR master.

 

No there isn’t, it’s a common leaking area for these M/C

 

I just found it kind of odd that the pedal goes way down, about an inch from the firewall, yet it is consistent. (Meaning always goes to the same point) never all the way down. Of course anything is possible, but if there was a leak you would think that it would push all the way to the floor

 

And the reservoir would be empty.

 

Sounds like an internal leak.