Brakes Not Releasing

[Jerry]

I have a new master cylinder on a 64 BJ8 and I think it has issues. Worked fine, the car only has 150 miles on it. But now the front disc won't completely release. Tight enough so you can't push the car. I am thinking that the Master cylinder is not releasing since both fronts are binding. I released the pedal from the master but the front disks did not release. I am thinking that the release hole in the master has a bit a debris? All the brake parts on the car are new so I don't know if that can be the problem.
Any ideas?

 

[kodpkd]

Did you rebuild the calipers or replace with new ones. I assume the hoses to the calipers are new.

 

[John Turney]

Did you change the pushrod from the pedal to MC? I had one that would not allow the MC to completely retract and open the port to the reservoir.

 

[red57]

I've never had a BJ8 but I think they were all boosted from about '63 onwards? Is it possible for the booster to not release completely?

 

[Jerry]

Calipers, hoses and brake pipes are new. It is possible for the brake booster to get stuck. This unit was rebuilt in Palo Alto. I don't know how to test the booster. Ideas?

 

[Jerry]

Just found this for testing the girling power booster.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://irp-cdn.multiscreensite.com/aa4b2dfa/files/uploaded/GIRLING%2520REMOTE%2520SERVO%2520MKIIA%2520%2526%2520MKIIB%2520OVEHAUL%2520%2526%2520FAULT%2520FINDING..pdf&ved=2ahUKEwj567SA9O_7AhVSOH0KHTe6AFIQFnoECDAQAQ&usg=AOvVaw14ExeI67Mb3Sca9N_4mUvs

 

[mezy]

You could try cracking the front pipe at the master, if that releases the front brakes, your looking master end. If brakes still holding your looking pipes or calipers

 

[Jerry]

Testing via the instructions for the Girling Power above showed the piston sticking. I have never taken one of these units apart. I was told the rebuild is an "ART". Easy to mess up. The original power brake was rebuilt by Power brake Exchange in San Jose. the paperwork says it has a one year warranty which is passed even though the car was not run during restoration. Anyone have a solution for the sticking piston that is easy ? or used Power Brake exchange enough that you would think they would honor the warranty?

 

[Bob_Spidell]

I've met the guys at PBE; delivering and collecting a servo for my dad's '46 Chevy truck (I lived in San Jose at the time). I met the tech that rebuilt Dad's servo (he had a Girling, from a Jag, IIRC, on his bench). Their shop is pretty grimy, as you'd expect, but they were quite cordial, you could give them a call and see what they suggest, they may have some 'tricks' you could try.

There are three cylinders in a Girling servo, a master that operates a slave cylinder which operates a T-valve that gates either vacuum or ambient air into the large piston in the canister (technically, a cylinder). Which one do you think is stuck (probably the air/vacuum piston, but the hydraulic section could stick as well)? If you have the Mk IIA servo you can open up the air/vacuum canister--you might damage the gasket--and see if you can persuade the piston to move (but the PBE guys probably wouldn't touch it after that). The air/vacuum cylinder/canister is lined with a dry lubricant that could be worn causing the piston to stick, and sometimes the leather seal will stick if the rubber tubing backing it up is cut too long. Either/both of the hydraulic seals could be stuck as well, as could the 'gland' seal that seals the rod on the air/vacuum piston (they're what often gets brittle and fail, allowing brake fluid to get sucked into the intake). There is also a check valve on the vacuum inlet, which permits some assisted braking if the engine quits, but shouldn't otherwise affect operation of the servo.

I've successfully rebuilt a Mk IIA, but gave up on a Mk IIB when I lost some parts.

 

[Jerry]

Servo is out and sent back to the rebuilder. Messy job once you have the fenders on. They said they would have the unit back to me in 2 weeks.