Brake System help

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Joined
Apr 22, 2024
Messages
14
Reaction score
14
Location
Moorpark, CA
My Car
71 Mach , 351C, 4 Spd Top Loader
Hello Folks,
I'm new to this site, just signed up. I've owned plenty of classics and still have a 71 Mach 1, 351C M code, 63R interior.
I've done plenty of brake jobs, Wilwood conversations, etc. over my lifetime, but this one has me baffled and I'd like some recommendations or confirmation of my thoughts.
I had a bad MC, so I decided to invest and rebuild the entire brake system. My Mach 1 has power front disc and rear drum. I replaced the MC and the VB, the combo valve, brake warning sensor, new stainless steel lines, pistons, calipers, pads, linings rotors and drums.
I made (or perceived to have made) the proper adjustments when installing the VB to the MC, rod extentions and such. Bench bled the MC. When bleeding the system, I used a centering screw in the combo valve to keep it centered. There are no leaks.
What I am experiencing is: on the first push of the pedal, it goes to the floor. Then pumping the pedal, it will build to pressure and will hold the pressure. When I let off of the pedal completely, the next "first" pump will go to the floor and upon pumping, it will get to pressure and hold.
My thought is that I have received a bad MC, but I'm not sure of that. Typically a bad MC will not build and hold to pressure. When bleeding the MC, there was nothing out of the ordinary.
So, do I replace the MC, re-bleed it, or is there something that I've over looked?

I appreciate your input,
Charlie B
 
Welcome from Plano, TX

I would loosen the mc and verify the actuator rod length. I measured in the mc plunger distance then used that to set the rod with 1/32 space.

If the rod is to long the mc won’t go back far enough to “reset”

A quick check is to loosen the mc some and try the pedal. If it works normal that is the issue.
 
Folks,
I finally got back to working on the brakes. Everyone's advise was very good. I went back through everything from the new MC & VB, everything seemed to be correct. I did have the calipers on the wrong sides. I put it all back together and it works perfectly.
I thought to myself about why Ford didn't put the caliper placements in the shop manual. So I went back into the manual and there it was, in black and white. Never too old to learn.
Thanks to everyone, I appreciate your help
 
Great post and responses. I'm digging into the brakes on my 72 now and this will help. Didn't know about having to use a centering screw in the combo valve to keep it centered. COOL!
 
Great post and responses. I'm digging into the brakes on my 72 now and this will help. Didn't know about having to use a centering screw in the combo valve to keep it centered. COOL!
The centering screw is not absolutely necessary. I've done the brakes on old fords dozens of times without one. Thats more of a solution for an uncommon issue.
 
Folks,
I finally got back to working on the brakes. Everyone's advise was very good. I went back through everything from the new MC & VB, everything seemed to be correct. I did have the calipers on the wrong sides. I put it all back together and it works perfectly.
I thought to myself about why Ford didn't put the caliper placements in the shop manual. So I went back into the manual and there it was, in black and white. Never too old to learn.
Thanks to everyone, I appreciate your help
Glad you figured it out.

Thanks for reporting back.
 
The centering screw is not absolutely necessary. I've done the brakes on old fords dozens of times without one. Thats more of a solution for an uncommon issue.

Same here. My thought is that if you can't get the valve to re-center on it's own, it needs to be rebuilt anyway.
 
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