Brake System help

[Charlie71]

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

 

[Sheriff41]

First, welcome to the forums!

Confirm you have the calipers on the right sides? They can be installed on either side so it can be confusing. @Hemikiller provided us with this illustration to help.

 

[NOT A T5]

Curious...what's a Wilwood conversation?

 

[Charlie71]

LOL..late night spell checker
That would be conversions ..

 

[James561]

Sounds like you need to rebuild/replace the power brake booster.

 

[rcadd1ct]

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.

 

[72mokk1]

First, welcome to the forums!

Confirm you have the calipers on the right sides, they can be installed on either side so it can be confusing. @Hemikiller provided us with this illustration to help.
View attachment 88035

Damn, now I need to go check mine.

 

[Charlie71]

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

 

[GERMYS_72]

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!

 

[giantpune]

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.

 

[rcadd1ct]

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.

 

[72conv]

I did have the calipers on the wrong sides.

Exactly why I do this kind of work one side at a time! Can't mix 'em up that way.

 

[Hemikiller]

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.

 

[canook2u]

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

gravity bleed the whole system. put it up on blocks & let the suspension go to full droop, (wheels off, obviously). start w/ RR, then LR, then RF, then LF.
whatever you do, do NOT let the reservoir go empty during the process or you'll have to start all over. . . .may take 1-1/2 to 2 quarts.