67 Drum Master Cylinder Question
I have a 1967 GTO with all drums and no power boost.
I recently noticed a drop in brake fluid. I keep a catch pan under the car (just in case!) and thought it was coming from the distribution block. After a thorough search I could not find anything leaking. I had my wife apply pressure to the pedal and immediately noticed a tiny squirt out of a hole on the passenger side of the master cylinder. The hole is about a 1/4 inch diameter and all the way at the back of the cylinder, just in front of the mounting flange. Is this a breather hole and the fluid is showing a seal failure (fluid leaking past the seals on the plunger)? Or did something loosen and fall out of that hole such as a set screw plug? I can't get a good look in there to see if it has threads or not and I could not feel any with a screwdriver tip. I also can not find a picture of the passenger side of a master cylinder online. Can anyone explain that hole? From what I can tell, it might be the original master cylinder so a failure would not be unexpected.
Also, rebuild or replace? I'm thinking the price of a new one is relatively low so I might replace and after the summer, rebuild the original. Appreciate any help.