I had to replace the rear brake line that runs from the front valve to the rear T. I can't get the brakes to build pressure. I'd imagine that it will take a little bit of pump'n to get the fluid to the rear brake. I get fluid to the ps rear but not to the dr rear.

I noticed that when I push on the cover for the master cylinder I hear air escaping. I'm wondering if that is ok? Can anyone tell me if theres does this?

 

I had to replace my drivers side caliper, rotor, and pads today, and before I did, I took off my master cylinder lid. One side was way low on fluid, and the accordian like rubber was extended down. So, with a clean paper towel, I pushed the rubber back in, added a little DOT3 brake fluid, and put the lid back on, pushing down on the 4 tabs of the plastic cover. When I did, I heard the air escaping that you seem to have described. I too hadn't heard this before on other, older cars from metal master cylinders w/ metal lids and the metal clamp down on top.