Tonight, I decided to try a master cylinder with a smaller bore. The one I've been using is for a 1968 corvette with power brakes, 1 1/8" bore. The one I want to try is for the same vehicle with manual brakes, 1" bore. I have manual brakes.

Anyway, I got it installed, and the front brake circuit would not bleed. I tried the two person method - 1 handling the screw, the other handling the pedal. I also tried a vacuum pump. I also noticed that the master cylinder would not make a little fountain in the reservoir when the pedal is pressed.

Both cylinders allow the pedal to travel to the floor so they aren't bottoming out. The 1 1/8 cylinder might require 1/3 of the available pedal travel to stop the truck and so there should be plenty left for the 1" bore.

I think it's a bad master cylinder. What do y'all think? have manual brakes.


Lawrenceville, GA