Brakes sticking...

[onetuford]

I just got my manual disc conversion done, bled the master and got fluid to all the wheels. Pedal felt good. Problem is the front brakes are staying locked up. I can spin them only after I crack the bleeder. The calipers are used, but the hoses and lines are new. The Proportioning valve is used. The master in a new reman unit. WTF? (that means what the frick )

[fordman]

a clogging of the system somewhere . you would mostly expect a clog in the calipers since they are used. but it could also be the rubber lines if they are used. they could collaps on the inside and not even see it from the outside. the next thing to look at would be the proportioning valve. if they calipers or valve werent rebuilt before use they could have disloged soemthing inside of them and sent that into the brake lines and made the clog also. i'm not sure your brake rod would have anythign to do with it. but what did you end up doing with that?

[onetuford]

The lines are new. The master is new, it seems to work, bled just fine. I've got another P-valve I could try after I attempt to flush the system a bit. My rod shouldn't be the problem at all. I was able to find the parts from the old master that hold the rod, sort of a barbed washer thing. I had to pull the internal snapring out and install it in the new master. I then cut a piece of the end of the new rod that was too long, and used it to "fill" the hole that was too deep for my existing rod. With the clip that came on that piece installed, it will never come out. With the clip installed for my existing 67 short rod installed it won't come out either. I effectivly shortened the depth of the well in the piston with the new rod.

[BlueOvalDave]

prior to going to the C V swap, I experienced the same thing. I initially switched the girls 67 to disc from a donor, but used new calipers, rotors pads hoses master etc. The only thing I used from the donor was the booster and I beams/spindles. I've done plenty of brakes, stock, aftermarket etc but it had me perplexed. Everything fit up and bled out fine but just the weight of the pedal on the booster rod was enuff to stop the front discs from releasing. If you were to pull up the pedal with your foot everything functioned normally. I used several diff proportioning valves with the same result. In my mind I narrowed it down to the booster/rod length. I never dialed it in cause I went to the CV set up.

You dont by chance have those residual/restrictors in the master that keep a slight amount of residual pressure on the rears mixed up do you?

Just a thought.

[onetuford]

You dont by chance have those residual/restrictors in the master that keep a slight amount of residual pressure on the rears mixed up do you?

Just a thought.

No, I don't think so. I bought a new master for a later model truck with discs and the brake lines to the P-valve came from the donor truck. But, I did have to remove the internal snap ring in the master and add the retainer lock thing and a washer for my short rod, a total of maybe 1/16" or 3/32" that in essence pushed the piston in a little. If that is the cause of it that is going to be a real PITA.

I wonder in your case Dave if the longer rod from the booster was the culprit. I'm going to try to push some more fluid through before I rip the master out to remove that washer...

[BlueOvalDave]

well, i;m telling you, it didnt take but the slightest pressure from the weight of the pedal assembly itself to stick the calipers.

Can you lift up on the pedal and see if that releases them?

That modification that you were forced to perform just might be the culprit.

[fordman]

i kind of had the same idea when i posted the first time. it could be the length of the brake pedal rod. one thign to try is to get the to lock up. and then remove the brake pedal rod and see if they release. if they do the rod is too long. if they dont you are back to flushing the system out. removing the pedal rod will probably take very little time vs flushing the system out.

[thorn1968]

No, I don't think so. I bought a new master for a later model truck with discs and the brake lines to the P-valve came from the donor truck. But, I did have to remove the internal snap ring in the master and add the retainer lock thing and a washer for my short rod, a total of maybe 1/16" or 3/32" that in essence pushed the piston in a little. If that is the cause of it that is going to be a real PITA.

I wonder in your case Dave if the longer rod from the booster was the culprit. I'm going to try to push some more fluid through before I rip the master out to remove that washer...

What year master did you get? I'm guessing that that 1/16" difference is keeping the MC piston from returning and releasing the pressure to the brakes.

[onetuford]

1973 to 1978 manual disc brakes. In order to remove the retainer for the old short rod I have to remove the master. It's held in place under the snapring that holds the piston in. I'll worry about later this week.

[fordman]

you don't have to remove the rod to check it. just unbolt it from the brake pedal.

[onetuford]

you don't have to remove the rod to check it. just unbolt it from the brake pedal.

I had to leave it bolted and then the stick I was using to push and hold the pedal a bit fell and I wound up having to try and remove the snapring with a side cutter (no snap ring plier) while holding the pedal with the side of my face, remove the two retaining washers and then reinstall the snapring with a screwdriver. All because I thought bleeding the master again would be a pain. Anyway rhe brakes work again now.

[fordman]

so the fix was the master wasant closing all the way?

[onetuford]

so the fix was the master wasant closing all the way?

yep. The pedal rod retainer consits of the barbed like washer and another washer over that that goes between the snap ring and the master piston. It didn't allow the master piston to return all the way.

[thorn1968]

Cool! Wish there were some pictures to go with this story.