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Brakes Not Releasing

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J

Jerry

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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?
 
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.
 
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?
 
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?
 
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
 
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?
 
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.
 
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.
 
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