Hello. Sorry for the delay in proceeding with troubleshooting.
To recap: Ten years ago I "overhauled" the rear brakes. They worked fine for the few times I drove it. I haven't started or driven this truck in 2-3 years, but I recently fired her up (thanks to the guys in the Electrical Bay). My current symptom is my brake pedal goes to the floor with no resistance, and the master cylinder is bone dry. So I started this thread and received a few suggestions. Yesterday I filled the MC with brake fluid. I did not bleed anything, out of laziness. The brake pedal again just goes to the floor with no resistance. I let it sit overnight to see if I had a leak, which I do not appear to; the reservoir is still full of fluid, and there are no signs of leak on the floor. I did remove the rubber boot and there was no fluid inside it (good thing).
I would've thought that I would get SOME resistance from the pedal, even though all I did was add fluid without opening any bleeders.
You will see from the attached picture that the bottom of the MC is very rusty, almost as if the fluid leaked out slowly over time and caused rust, without creating a puddle on my floor (although I did have cardboard down and couldn't tell a new leak from an old one).
Please advise on next step in troubleshooting. Is it invalid for me to just add fluid and pump the pedal and expect some pressure? Maybe some part of the MC is not doing its job in pressuring the system. But where did my original brake fluid go over the last 2-3 years?
