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why brake pedal won't release

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steeters View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote steeters Quote  Post ReplyReply Direct Link To This Post Topic: why brake pedal won't release
    Posted: Jan/09/2009 at 11:06pm
Okay, the subject line is a "hook."
 
The real deal is that my '70 Javelin never ran when I got it (still doesn't run, but getting close to that big day).  All I know about the brakes is that it has a drop of fluid in the master cylinder (front disk rear drum) and that, get this, someone previously ran a spring from the brake pedal to the dash board.  It appears that this was some attempt at getting the brake pedal to come back up from the floor after it was applied.
So, I'm going to assume that the previous owner discovered that when they applied the brake pedal that the pedal stayed on the floor, and that this spring somehow got the pedal back to its original position.
Any suggestions as to what the real problem was that causes this condition, and what I need to do to correct it?
 
Thanks!
 
Steve
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Jan/09/2009 at 11:41pm
I'd say your master cylinder needs to be rebuilt.  Joe
Happiness is making something out of nothing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote steeters Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2009 at 10:05am

Is the pedal not returning to its original position an issue of a bad (brake) vacuum booster?  Is there a process to solving this, like: First replace the master cylinder to see if that solves the problem, and then 2) replace vacuum boster?  Or just replace it all?

Thanks!
Steve
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2009 at 10:25am
the test for a bad booster is with pressure on the pedal, start the engine, and the pedal should "fall away" under your foot, as the vacuum booster makes it easier to push...
My guess is that the spring does not indicate anything about the condition of the brakes.  bleed the brakes, see if the pedal is hard, if not, probably really do need a master cylinder.  then test the booster once the brakes are functional.  Should be able to push the car, hold the car with the brakes, and then when the pedal is released push the car. 
BB
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pat D Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2009 at 10:50am
There is yet another circumstance that would result in the brake pedal being attached to the dash with a spring, I've had to do this myself. Where is the brake light switch? If it is connected to the pedal under the dash, it may be that when the car is parked nose down, the pedal may sag just enough to activate the brake lights when the car is unattended, thus leaving a dead battery, or at a minimum, phone calls from concerned neighbors. You won't really know until you rebuild the system and get it fully functional.
Pat in MD
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bigbad69 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2009 at 5:20pm
Originally posted by Pat D Pat D wrote:

... the pedal may sag just enough to activate the brake lights when the car is unattended...
Why not just adjust the switch so the brake lights don't come on until the pedal is given a real push? Easier than rigging up a spring.

However, if the pedal goes to the floor and stays there, there is something wrong with the brake system. Maybe the PO saw the overcentre spring on a clutch pedal and thought the brake pedal was missing it's spring. You won't really know what (or if anything) is wrong until you bleed out the brakes and test them.

69 BBO Javelin 390 T10
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/12/2009 at 9:13am
My SC/Rambler initially had the brake pedal being pulled to the floor so I just gave the booster hose a quick squirt of CRC 56 lube and that was the end of that.  The flapper (my name not the the official name) diaghram on the rebuilt booster was stuck from sitting for so many years and just needed a little bit of lubricant to free it up.  It stopped pulling the brake pedal as soon as the squirted in the little shot shot of lubricant and works fine now.
Dan Curtis, AZ AMC Collector Quality Restorations & Parts - amcmusclecars.com
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/13/2009 at 3:28pm
The booster does have a big spring in it to help return the pedal (well, the diaphragm in the booster, but it's connected to the pedal...). Could be broke, and the external spring would work if that's the case. The brakes should otherwise work well.

I'd start by checking the brakes for proper operation with the spring still connected. Crank the engine with pedal pressed, it should go down. Release pedal should come up, and you should have a good pedal feel when you press it again. If all feels right, disconnect the spring and try again. That should at least reveal if the spring is there because of a booster problem.

The spring could be there because the brake light switch wasn't contacting the pedal enough. Either the PO didn't know how to adjust the switch or that it could be adjusted, it's the wrong switch and won't adjust far enough, bracket bent, etc. I've seen some stupid things done even when a minor adjustment would have correctly fixed the issue, so don't rule out the brake light switch until you check it!

If all seems well, best to jack up the front, put it on jack stands, spin a tire, then hit the brake. Repeat on other side then do rear. If all seems well it's time for a road test, but do find a safe, level area before actually taking it out on the road! Might want to check the park brake before doing this too.

I know that last sounds like a no-brainer, but some who read this might be new to working on cars and not think about it until too late. I know I've occasionally had something "go wrong", and then think that the preventative measure was obvious! Like getting shocked by a wire I thought was disconnected when wiring my house addition yesterday. Was just a surprise, no harm done, but turning off the breaker just-in-case would have been the wise thing to do, even though I thought the other end wasn't connected yet! Apparently I DID connect it in a junction box under the house... could have swore I left it disconnected! Got the "reminder" instead...
Frank Swygert
American Motors Cars Magazine
www.amc-mag.com
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