i have a 2007 HHR and was wondering the best method of loosening and tightening the rear brake line on the master cylinder. Is there a special tool for that?

 

I'm not sure what you are asking, but my looking at the master cylinder thinking about replacing it led me to believe that you MUST remove the fuse box to get to any of it.

 

And use what's called a Flare Nut Wrench, because if you round off a brake line fitting, you're day will go straight into the "can't possibly suck anymore" catagory.

You can pick up a decent set of Flare Nut Wrenches at Harbor Freight in both SAE and Metric for less than $40.

And Don is correct, you'll need to move/remove the fuse box to gain access thank to the HHR's 10lbs in a 5lb sack underhood layout.