A sinking pedal indicates a leak or a failed cylinder. If no leaks and the fluid level is good then you need to look at the rear brakes or a bad master cylinder. The MC can fail internally causing a low pedal with no outside leakage. Calipers only leak or seize. They don't suddenly cause a low brake pedal without one of those issues. Dragging or over heated brakes can cause the fluid to boil causing a vapor condition. Your questions seem to indicate a lack of knowledge. You may want to get some help so you can things fixed and continue with your trip . 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Vincent Dow
Sent: Sunday, July 5, 2015 8:17 PM
To: vanagon@GERRY.VANAGON.COM
Subject: anybody done the brakes on 1982 gas westfalia?

Howdy,
Had the braking power seriously diminish on my 82 westy. What a bummer, we were headed to San Luis Obisbo county, to bring the dog up to a beach (and
ourselves)

Had to turn back to L.A. at Thousand Oaks.

The brake pedal felt tall in the morning when we started out. 50 miles into the drive, I felt the pedal bottoming. A couple pumps with my foot would do the job, but I knew I was losing pressure.

I got the wheel off, and am looking at the caliper. The flexible brake line is attached to a bracket, that's under huge nut for the main big suspension piece whose name alludes me. The one that's under spring tension.

I'm thinking I have to open up the brake line and drain before I can even get the pads out. Haven't come across a caliper like this before. Don't like it.

I'm wondering if I shouldn't rebuild calipers now. I'm seeing lots of pics of nasty old ones. Brakes are important. Does this ring true to experienced owners? Bit the bullet and rebuild the caliper? Or is that going overboard?