Just wanted to let everyone know that I did what a couple others here have suggested and fixed my leaking reservior.

Got a 1 1/2 OD rubber O-Ring gasket that was 1/16 thick. Took out the baffle from the cap. Put the O-Ring in the cap and put the baffle back in over the O-Ring.

Fits snug and no leaks.

I tried a thicker O-Ring before, but it was a bit too thick... the 1/16 worked like a charm

Not that I'm recommending you do this before talking to your dealership or mechanic... but I figured I'd let people know it fixed mine too

 

I did another suggested fix which was to remove some of the brake fluid on my 06 GT. It is now approx. 1/4" below the full mark and no more issues...