I have been looking through the posts on brakes and haven’t quite found what seems to have happened to me. A couple of times during the last two weeks, my brakes seemed to stick but released when I depressed the pedal. Today, as I was pulling into the driveway and breaking gently, the brakes locked up and the pedal is locked in the up position. I can’t depress the pedal nor release the brakes. I need some direction.
Thanks
Try popping open the front bleeders: see if that releases them.
The bleeders at the calipers? Just want to make sure.
I was checking fluid levels and all seem fine, although the one on the right could use some topping off. I did see that the fluid level detector housing was looking pretty bad on the center cannister
I opened the front bleeders (and then closed them) Nothing happened. No fluid escaped. No change in the pedal which remains in the full up position and does not depress.
Strange.
Sounds like an issue with the slave master: others on here are better with that bit of alien technology!
The corroded aluminum gets reduced to a sand-like powder which is mostly captured in the bottom of the bottle by the little filter bag over the outlet tube. If that bag is missing or damaged then the powder goes into the rest of the system and if the bag is present it is still possible for some of the fines to get past it.
Did you attempt to depress the pedal while the bleeder was open?
Will look for the bag and clean if appropriate.
I did not attempt to depress pedal but I certainly can try that.
I was reading some of the older posts and one suggested blocking off the vacuum at the manifold. Might try that but not sure if its is appropriate.
the thing that just seems strange is that the pedal is full up but the brakes are locked.
Try cracking the pipes from the master cylinder to see if the pedal moves. Have plenty of rags around the area to catch any fluid, and a bottle of water to wash off anything that gets into your paintwork.
Do yourself a favor and slip a piece of tubing over the bleed nipple and direct the tubing into a catch bottle. It doesn’t need to be fancy. I knocked this together with stuff I had laying around. The last thing you want is brake fluid spraying around the garage.
1 Like
Thanks. Will put something together.
George, you say the pedal is locked in the up position. There should be the mechanical free play at the top of the pedal stroke, the about 1/16 inch clearance between the push rod and the MC piston. If the pedal is indeed locked all the way up, check that first.
Tom
Well, the mystery continues. I went out to check the free play at the top of the pedal this morning as suggested by Tommd55) and there was plenty!! 
Very puzzling. So I started her up and backed her up a bit AND THE BRAKES WORKED.
I think I will go buy some vacuum break hose and start replacing what I have (any tips would be appreciated especially relating to the easiest way to run the hose from the manifold). In reading some of the older threads, it was mentioned that the vacuum hose can deteriorate from the inside and lock up the vacuum assist. Maybe that is what is going on. Anyone ever run into this type of situation where the brakes lock up and then release on their own over a period of time?
“brake hose”, oops excuse the typo.
Brake lock up is common. What isn’t common is the pedal hanging up. Nothing in the vacuum or slave cylinder would account for that. If I ever found a brake sensor that looked like that, my inclination would be to rebuild the whole system.
Did somebody mention clocked up brake hoses, or does that not fit the symptoms?
George, if you did not, you need to check the physical free play at the rod.
Tom
For the pedal to be completely locked up in the up position, the compensating port must not be being uncovered and there must not be any physical free play, if that indeed is what has occurred. That is why you need to check free play.
If when you opened the front bleeders, no pressure was relieved, but the brakes remained locked, you probably have additional issues.
But start with the free play.
Tom
Thanks Tom. I am a bit new to working on this car so I am running into a lot of things I have never seen on my 57 TBird.
The first question relates to the free play. I assume you mean that I should be able to “wiggle” the brake pedal by hand while it is in the up position. I have checked that and it does move up and down about 1/16" or so. Now that the brakes are working again, Maybe I should bleed the front breaks a bit although I am not sure what that might do.
I have seen the comment that Michael made earlier (and I have seen it in some other posts). If it is common, what do people do? Let it sit overnight like I did? Still think I might replace some or all of the vacuum line.
By the way, while I was examining the brake pedal, I noticed the rubber seal on the clutch posts was allowing fluid to seep out. OUCH. Might have to start a new thread on that issue.
This is where it is hard to be sure we understand exactly what is being done. The 1/16 is at the push rod at the mc . 1/16 at pedal is probably not enough as it probably leaves almost nothing at the rod.
Tom
Something similar happened to me yesterday with my '72 XKE. The brakes started dragging and I had to stop and investigate.
I figured that there was a small air leak in the reaction valve to brake servo, causing the brake servo to push on the slave piston which in turn dragged the brakes. Luckily, I was in a mall parking off the highway and went to a sporting goods store. Got a screwdriver and some golf tees. I used the screwdriver to disconnect the vacuum reservoir from the manifold and used a golf tee to plug that hose to the manifold to keep vacuum there.
It worked! No more dragging. I guess that a slightly bigger leak could drag the brakes even more.
I will figure out where this leak originates but in the meantime, you can use the master cylinder to do the braking manually. It’s less effective and requires more force but it will get you home.
So my 2 cents is for you to try this & check for vacuum leaks between your reaction valve and the rear of the brake servo.