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GaryBudd

29" DeSoto brakes again

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I have to be missing something.I have bleed brakes at least 6 times at each wheel,still no back pressure.I had the brake pedal to the floor and not one wheel locked up.There are no leaks anywhere,when the brake pedal is pressed fluid and air come through.I did rebuild the master cylinder and I will admit I didn't bleed it.It seems like that couldn't be the problem.Just went through them again,same ,no back pressure.Any ideas?

Thanks

Gary

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Will they pump up?

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Yep....sounds like the master cylinder still needs to be bled. The lack of doing that WILL cause you problems. Unless the master cylinder is bled, you may still have air inside it. That air will just transfer back and forth and NOT go away. As an ex-brake mechanic, I can attest to that. I certainly could be wrong about yours. Did you say that you adjusted the brakes as mentioned in another post, to where you can hear a little rubbing of the shoes on the drum?

Edited by keiser31 (see edit history)
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Hmm, Then either master cylinder problems or brakes are way out of adjustment.

Are you closing the bleeder valve while letting the pedal back up? (I guess there could still be lots of air in the lines if you are getting air and fluid).

The procedure would be to start at the furthest wheel from the MC.

Have someone sit in the car, open the bleeder, then have the guy push the pedal down, close the valve before letting the pedal back up.

Wait a few seconds and do it again, repeat until you get straight fluid.

All the while making sure the master cyl reservoir doesn't go empty.

Then move to the next furthest wheel and so forth.

The old idea of a tube in a bottle doesn't work for me as you will get air back thru the threads of the bleeder.

The very best would be a pressure system over the master cylinder, but those may be hard to find let alone adapt to your MC.

 

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Keiser posted while I was typing.

Yes, master cylinder has to be bled out first. Very important.

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Is there the possibility that you may have used the wrong master cylinder rebuilding kit??? When you installed the piston did it go right in without having to work the cups into the bore of the cyl.?? If it did then the cups and /or piston is to small.  Before you remove the master cyl. again  remove the lines and plug the hole with your finger and have someone press on the pedal and see if the fluid sprays out. It just came to mind I had a neighbor come over complaining of that same problem on a 55 Ford. Said he has had a number of people look at it but no one could find the answer. I removed the master and found that the piston he used for the rebuild had to deep of a tunnel in it where the push rod from the brake pedal rest. The push rod was being allowed to move in without moving the piston. I had to replace the piston in order to bleed the brakes.

Edited by retiredmechanic74
further information (see edit history)

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OK first of all it's 56 degrees in Upstate NY today.I took a deep breath and went over all your suggestions and happy to say I have brakes now.I believe the master cylinder was my biggest problem,bleeding it that is.I also found one wheel cylinder leaking.I have said it before the guys in this group are the BEST.I am a one man army doing something I have never done before and I love it.

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