Brake booster rod hanging up!

Can someone tell me the reason(s) why when I press my brake pedal there’s a spot where it hangs up on return and then “pops” up as it returns to original position.

This is on a ‘73 barracuda. I have a new master cylinder, booster and clevis pivot. I have had this thing on and off a million times.

Thanks !

When nothing is attached to the brake pedal, does it swing freely?
Was this problem present with the old master cylinder?
When you bench bled the new master, did the plunger return freely?

You could have a brake pedal pivot issue.
You could have a new master cylinder problem.
You could have a linkage binding issue. You need to test each possibility on its own.

When you step on the pedal, your foot pressure overcomes the problem, but when it returns, it relies on the internal master cylinder springs to push everything back. Gene

I am creating this system from new. The car had no brakes when I got it. I have tried to test the components individually for binding, I have bench tested the MC and have even taken it apart to inspect. I am also thinking I may have binding or misalignment at a pivot point. Hoping the two heads better than one thing will help me here.
Thanks!

Gene's got ya covered. (grab a helper to work the pedal with you eyeballing the linkage).

I’ll try that.

One suspect for misalignment is the location of the hole where the clevis attaches on the brake pedal itself. It’s obvious the hole in the pedal arm had been filled and redrilled. I tried to relocate it from clues left on there. If I had a reference for this measurement that may solve part of my problem

You need to eliminate the things that are good from the process.

If the plunger on the master cylinder returns back out smoothly, the master is OK. If, however, the plunger comes back out in steps, or stops/delays a few times, the master may well be the problem.

The brake pedal is also pretty simple to eliminate. It either swings freely when nothing is attached, or it doesn't. If it doesn't, find out why before you go to anything else.

If the master is good, and the pedal is good, you have a linkage issue.

When the rod that goes to the master is bolted to the pedal, it should also move freely on the brake pedal (some have a rubber "O" ring the won't allow them free movement, but they will still move without a bind), within the limits of how it can move. That rod should also move in alignment with the brake pedal. If it moves at a different angle, you need to correct that.

Unless you have an added pivot lever, about the only thing left is the rod's alignment with the recess in the master. Some minor up and down misalignment is OK, the pivot of the rod on the brake pedal will accommodate some of the up and down, what it wont accommodate is side to side misalignment. The master has to be inline with the brake rod attaching point on the pedal assembly. Nearly any side to side misalignment will cause a bind. You may be able to shim between the rod and the pedal. There may be enough side to side movement in the master mounting bolts to shift the master enough to get the alignment. As a last resort, you can modify the brake pedal, but make it the last resort. Another alignment that has to be correct is the master has to be mounted squarely with the pedal as it swings. They have to move with the same angle. If one moves at an angle in one direction, and the other moves in the opposite direction, a bind happens.

If you can't figure it out, post lots of pictures of your setup and how things move. I've scratch built this stuff from a pile of parts and made the mounting brackets, so I've been through this a few times. Gene

^^^ Ding ding ding I (do) believe we have a winna

Everything works fine independently.

The brake pedal swings free.

The clevis pivot is not binding and there are no weird angles.

I uninstalled the master cylinder, bench bled it again and it works like it should.

I took the booster off and depressed the plunger. It rebounds with no binding.

I made sure the plunger rod from the booster is properly seated in the booster.

Here are concerns
I bought a new firewall reinforcement plate/ clevis swivel kit and it was labeled (for mopar B and E body) but maybe not??

I'm going to install everything without the plate and see if I still have the binding. And if I do, I don't know what ima do!!

Suggestions appreciated !

thanks !

Without having any idea how the brake pedal bracket attaches to the firewall reinforcing plate, and how that plate might fit against the firewall, any answer we can give is a simple guess.

That said, I would suspect the plate mounting holes may be off just a bit causing the pedal bracket to shift just enough to make the pedal bind. If that is the case, enlarging the mounting holes in the firewall reinforcing plate just 1 or 2 drill bit sizes may give you enough adjustment to keep everything in alignment.

The second thought is that maybe the plate isn't sitting flat against the firewall, or its not letting the brake pedal bracket fit flat against the firewall. If that is the case, you have to correct whatever needs to be addressed to make the bracket sit flat against the firewall. A gap that shows daylight between the firewall and the plate or between the brake pedal bracket and the plate is enough to cause a bind.

We had a firewall with a bead roll around one side of the brake pedal mounting bracket. We added a reinforcing plate to add strength to the firewall that sat up on top of that bead roll on one corner. After we mounted everything we had a pedal bind, it took me hours before I figured out that bead roll was causing the problem. After I trimmed the plate, and smashed flat the corner of the bead roll, the bind went away. You would be surprised how little it takes to cause a bind, sometimes. Then there are other times where it doesn't seem to matter what you do, it will never bind. Gene