Brakes locked up. Need help!

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g49bridges

g49bridges

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Hey guys, I need some advice. I've replaced my entire brake system on my 74 duster. Everything is new. New calipers, rotors, drums, wheel cylinders, and flex lines (factory parts from o'reillys), all new steel lines, new proportioning valve from yearone, and a new master cylinder/brake booster combo from cpp. bench bled the master and everything was fine. Put it on the car and after 3-4 pumps the peddle was firm....but will not release. all four brakes locked up. After sitting for 2 weeks while I was away for work, it finally released enough to move a wheel by hand....but still dragging. I pumped it again....same thing. Took the master cylinder loose from the booster thinking the pushrod wasn't adjusted right, but even when I separated them the brakes stayed locked up. Only thing I have done to successfully release the brakes was to crack open a bleeder on the rear wheels. Anybody know what the problem could be???
 
When you removed the master from the booster was the piston back against the retainer? Sounds like it's not fully returning to expose the ports to allow fluid to return. Especially with all four wheels locking.
 
Betcha the piston in the master cylinder is pushed in too far and won't come back enough to release the fluid back into the master cylinder.
You can prove this easily by loosening the master cylinder to booster mounting bolts and the brakes should release.
If this is the case you have a few choices to fix it.
1. Back off the brake push rod
2. Get a shorter push rod
3. Space the booster and master father from the firewall.

I'll bet your pedal is at full up and tight when this happens right?
Make it lock and then loosen the master cyl bolts and if that is it, then it will probably make sense.

:D Typing at the same time, but at least we agree.
That ought to make the OP feel better.
 
Your screwed! (just kidding man). Hopefully it will be something simple like the master cylinder piston. good luck!
 
He said he took the m/c loose from the booster. Has to be the master cylinder.
 
Yes, I have taken the master cylinder loose....pulled it about 2 inches away from the booster, and all four corners stay locked. It kinda sounded like a master cylinder problem to me as well, but I'm not really that much of an experienced brake guy. I have not looked to see if the piston was all the way back out, but I will check that first thing when I get home this weekend. Been building this car for 2 years, and right now the brakes are the only thing keeping me from being able to drive it for the first time!!!
 
Easy proof for that would be to crack the lines loose at the master then.
It should let go.
If it does, then you got it whipped.
 
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