Odd master cylinder/braking issues

[MomsDuster]

This is a first for me. The car sat for a few weeks due to having stupid hot weather. Got in it to take a cruise and the brake pedal felt a little soft. Not mushy really but just a little soft. It stopped fine, didn’t feel any different in braking power or effort so I just wrote it off to not being driven for a while. Wife and I took it on a trip to the coast, 160 +\- miles round trip. All went well until we got into stop and go traffic on the way home. Then it seemed to have a brake drag. Could only feel it at speeds under 15mph. Felt like that for the last 15 or so miles. The car sat for a week and the next weekend took it out and no issues for most of the time until I got just about home and the drag was back but this time it had a shudder with the drag. Last night I put it up on stands, pulled the driveshaft and checked the joints. Put a stethoscope to the pinion and wheel bearings and all was good there. Then I pulled the wheels and drums and found a considerable amount of brake dust on the rear passenger side. Front brakes looked great. I popped the cover off of the master and fluid poured out of the front section of the master while the rear section of the master was at least half way down. Really weird! It appears that maybe there is an internal issue with the master or maybe the proportioning valve pushing fluid into the front section of the master causing a constant pressure on the rear brakes especially after multiple pedal depressions. Has anyone seen or heard of this? Is it even possible?

 

[Dana67Dart]

Manual or power brakes?

What you are describing sounds like a mc pushrod that is not adjusted correctly.

Not allowing the mc piston to return to it's full reward position

 

[MomsDuster]

Manual or power brakes?

What you are describing sounds like a mc pushrod that is not adjusted correctly.

Not allowing the mc piston to return to it's full reward position

Manual brakes, I will check that for sure. Seems to me that it would have had issues earlier though. I’ve got 5000 miles on this build.

 

[Professor Fate]

Disc/drum or drum/drum? Double check your self adjusters. If incorrect or on the wrong side they could be self adjusting inwards, causing the cylinders to expand and take up more volume of fluid (causing the low level in the master), to the point where the shoes get so loose they could feel spongy when the brake is applied, and **** a little bit when released causing some dragging and your dust buildup. Just a thought.

 

[MomsDuster]

Disc/drum or drum/drum? Double check your self adjusters. If incorrect or on the wrong side they could be self adjusting inwards, causing the cylinders to expand and take up more volume of fluid (causing the low level in the master), to the point where the shoes get so loose they could feel spongy when the rake is applied, and **** a little bit when released causing some dragging and your dust buildup. Just a thought.

Thanks, I’ll double check that also.

 

[Dana67Dart]

Manual brakes, I will check that for sure. Seems to me that it would have had issues earlier though. I’ve got 5000 miles on this build

Most likely not the problem than with manual brakes.

But it seemed that your issue has gotten progressively worse over time.

Professor Fate's auto adjuster thoughts are worth checking.

The MC could be sticking at the release end of the travel not allowing the fluid to go back into the rear resivour OR an internal leak from the front brake system to the rear brake system.

 

[MomsDuster]

Most likely not the problem than with manual brakes.

But it seemed that your issue has gotten progressively worse over time.

Professor Fate's auto adjuster thoughts are worth checking.

The MC could be sticking at the release end of the travel not allowing the fluid to go back into the rear resivour OR an internal leak from the front brake system to the rear brake system.

I’ll be checking that for sure. I was planning to convert over to the two bolt master this fall, maybe doing that sooner than I thought.