Brakes locked (?)

[FY1Cuda]

! was having trouble with a drip around the master cylinder, so I put another one on.  Bench bled the MC before installing. Measured the rod at the booster and the depth of the hole for it on the MC piston.  I lengthened the rod a bit and it seemed right. Drove it around the block to see if I could get away with not bleeding the lines right away.  Did some other engine adjustments in the garage and then backed the car out of the garage and checked the transmission fluid on a level surface(added a quart).  Went to pull it back in and the brakes were (are) locked and the dash brake light is on.  Brakes are still locked up but I drove it back into the garage.  Thoughts?

[Bullitt-]

Thinking that booster rod is to long now...

[Cudakiller70]

Is it front and back? Can you jack up your car to confirm? To double check your rod length you could loosen the 4 bolts that hold your master clyinder on, letting it slide forward about an 1/8" see if your brakes unlock, if not try a 1/4" to see if then they unlock. This may rule out your rod length too long. I'm not a brake expert by a long shot, but going through something a little similar. I'm suspecting my combination proportioning valve has my front wheels locked up.
Try bleeding all wheels throughly.  I'm watching this for my problem also . Jim

[FY1Cuda]

When I lengthened the rod, it was no more than 1/16" I moved it.   I just shortened the rod an hour ago back to maybe a tiny bit shorter than it was originally.  The rod has less than 1/8" adjustment left before the adjusting nut is fully seated.  No difference.  I'm also wondering if the proportioning valve is bad.  Raising up the car to check each wheel seems like a good idea.

[Cudakiller70]

My problem started when I replaced a rear caliper because it was stuck on. I took the caliper apart and found some crud, also the fluid was very dirty. The caliper piston was pitted and rough. PO didn't drive the car very much and from what I hear brakes can start sticking if the car isn't driven enough. Before replacing both rear calipers I flushed the rear lines only, then the whole system, but both front discs are now locked on? I think, we'll know now that the proportioning valve was dirty. I am going to rebuild it with a kit from here https://www.musclecarresearch.com/1970-76-mopar-combo-valve-rebuild and will see what happens. Jim

[FY1Cuda]

This car just got all new brake lines.  The proportioning valve was the only hydraulic piece left in.  I was getting a drip from the other (new) MC and bubbling my new engine compartment paint.  That's what prompted the change.  I'm having nothing but trouble with the master cylinder.  This is the fourth MC (my kid bought this one) I've put on this car now.  You can read my litany of woes:
http://www.cuda-challenger.com/cc/index.php?topic=106529.msg1045898#msg1045898
I kept getting a little drip at the fittings into the MC so I kept giving them another wrench.  Wondering if I've pinched off the tubes a little to constrict the flow back to the MC.

[Cudakiller70]

Read your other post ugh! I wonder if thier is only one current supplier of MC's and they substituted a part to accommodate their inventory. Your MC is not leaking now right?  I do not know if it's true, but I did hear not to push the MC piston in too far it's possible damage the seals. Check your E brake also to see if it's hanging up. Which wheels have locked? Where in the Bay Area are you? I have a pressure bleeder you could use if needed. Jim

[FY1Cuda]

Took the MC off, rechecked the length of the push rod, reinstalled it, and bled the brake lines.  The brakes were still grabbing, and it got worse as I maneuvered into the street.  Jacked it up on Cudakiller's advice and found that the rear brakes were locked tight.  Tried to turn the star wheel through the adjustment slot and couldn't move it. Going out of town in a few days so I don't have much more time to dick with this issue.

This last MC was an MBM that my son bought through Mancini's.  It was much more expensive than any one you'd get at Rock Auto, Napa, or O'Reilly's, and when it came, it was  coated in black with a black cap and black bale.  Maybe OK for Johnny Cash, but not OEM. Spent a lot of time removing the black coating, so even if this MC proves to be the issue, I wouldn't want a replacement black MC. I would put the one I took off back on if it didn't leak a little out the back.

Any ideas how to unlock the rear brake shoes?

I didn't have any locking issues with the previous MC, so I kinda figure that the master is the culprit.  Any thoughts on the subject are appreciated.

[Bullitt-]

Well if it's a build up of pressure opening the bleeder should remove that... do you have an appropriate brake tool for the star wheel?

[FY1Cuda]

opening the bleeder makes good sense. I should try that to see if it releases, but when my wife was helping me bleed the brakes with her pushing the pedal down and me cracking the bleeder, things seemed rather normal.  It seems as though something in the MC is restricting the backflow.  I have a brake tool, but I wasn't having any luck catching the wheel and turning it.

[Denison636]

I guess my first question before I can help is do you have drums on the rear. You talk about a caliper but also a star wheel.

[FY1Cuda]

Front disk/rear drums.  I read that the master cylinder for this setup has a "residual pressure valve" in the port to the rear brake circuit.  It provides a slight push on the fluid to offset the springs in the rear brakes. It seems as though the pressure to the rear brakes is not releasing, so I'm wondering if the residual pressure valve is not working right.

[HP_Cuda]

Could it be stuck? What happens if you open the bleeder valves on the rear drums?

[Denison636]

Start by backing your brake shoes off. It can be done you need to use a straight screw driver with your brake spoon.

[FY1Cuda]

We're going to be out of town for a few weeks so I'm putting this off for a while.  I'll tackle when I get back.