Low pedal.

Ok I am going to start with this issue.

Just drove the 1969 GTS from Orange to San Diego. Got here in one piece. A good portion of the trip was heavy traffic so on and off the brakes. As to brakes. Stocl Disc/drum no pwr.

Later in the trip I had a long run of high speed needing no brakes. So when I went to the brakes the pedal went halfway to floor. Talk about Holy Sh..... So I pump the pedal and the brakes come back up. But as the trip continues the problem happens more and more with shorter periods of no braking in between. When I got home I pulled the reservoir cover and the good news is there is plenty of fluid. Kind of dark actually. Not a good sign. So let me guess.

Likely master cylinder I am thinking. Could use some expert opinon though.