Dumb (?) Brake question - JeepForum.com

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post #1 of 11 Old 03-20-2017, 09:00 PM Thread Starter
jackler
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Dumb (?) Brake question

Let me apologize in advance for what may be a dumb question. I am trying to finish off my brake upgrade and am having a really difficult time getting the air out of the brake system. Here is what I started with;
new booster/master for Jeep CJ (ebay)
all new brake lines (hard and soft) front to back
all new front and rear brakes (calipers and wheel cylinders)
new proportion valve

I did bench bleed the master (2x) and have attempted to bleed the brakes a few times, both gravity and traditional two person method. The most recent time I had my helper depress and release the pedal at least 25 times, and I consistently had air coming out. Also never got a "firm" pedal. I am doubting a proportion valve problem at this point as I am always getting fluid out at all four corners, just too much air. I assume with all new parts and the system being "dry" this would be a longer process, but this seems wrong. The symptoms lead towards air be re-introduced into the system somewhere, although I have no leaks.
First question is, should I have a firm pedal after pumping the pedal in succession? Or would the pedal only firm up when hooked up to vacuum?
Second, any ideas on the next step?

Thanks for any help you can offer

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post #2 of 11 Old 03-20-2017, 09:44 PM
WindKnot
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There is a special tool that must be threaded into the proportioning valve to keep it from thinking the air in the brake lines were caused by a damage. There is a shunt that shuttles back and forth in the valve and it shuts off the flow of fluid to either the front or rear brakes so that your brakes don't fail completely. (or so it thinks...) Threading this tool into where the warning light switch fits blocks this shunt from moving back and forth and allows you to bleed the brakes.

There have been about 17 kajillion threads on this; it's a common dilemma for people trying to bleed their brakes after replacing the lines. Use the subject search. You will find much information.

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post #3 of 11 Old 03-20-2017, 09:57 PM Thread Starter
jackler
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Quote:
Originally Posted by WindKnot View Post
There is a special tool that must be threaded into the proportioning valve to keep it from thinking the air in the brake lines were caused by a damage. There is a shunt that shuttles back and forth in the valve and it shuts off the flow of fluid to either the front or rear brakes so that your brakes don't fail completely. (or so it thinks...) Threading this tool into where the warning light switch fits blocks this shunt from moving back and forth and allows you to bleed the brakes.

There have been about 17 kajillion threads on this; it's a common dilemma for people trying to bleed their brakes after replacing the lines. Use the subject search. You will find much information.
I have read alot of those threads, they all seem to share the fact that they can not get fluid to one end (or the other) of the brakes. I am not having that problem, I have plenty of fluid coming out, just can not eliminate the air.
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post #4 of 11 Old 03-20-2017, 09:59 PM
hickslawns
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It is also possible you got a bad master cylinder. When your helper pumps the brakes can you hear an air swooshing sound?

Second thought I have is more of a question. Not to make you feel foolish or look foolish. I do not know how much experience you have. Forgive me if this sounds insulting. How are you pumping the brakes? If he is pumping and releasing it isn't doing much. If the helper pumps the brakes until there is some pressure and then holds the pedal down as you open and close the bleeder, this is how we do it. Once your bleeder is tight the helper can pump again until they are firm. Once firm the helper holds the brake pedal down until you open AND close the bleeder. I was taught to always start farthest away from master cylinder. Right rear, left rear, right front, then left front. Be sure to check the reservoir periodically as well to ensure you haven't run it dry.
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post #5 of 11 Old 03-21-2017, 06:40 AM Thread Starter
jackler
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Originally Posted by hickslawns View Post
It is also possible you got a bad master cylinder. When your helper pumps the brakes can you hear an air swooshing sound?

Second thought I have is more of a question. Not to make you feel foolish or look foolish. I do not know how much experience you have. Forgive me if this sounds insulting. How are you pumping the brakes? If he is pumping and releasing it isn't doing much. If the helper pumps the brakes until there is some pressure and then holds the pedal down as you open and close the bleeder, this is how we do it. Once your bleeder is tight the helper can pump again until they are firm. Once firm the helper holds the brake pedal down until you open AND close the bleeder. I was taught to always start farthest away from master cylinder. Right rear, left rear, right front, then left front. Be sure to check the reservoir periodically as well to ensure you haven't run it dry.
This is not insulting at all, thanks for the response. I do hear air moving in the master when the brake pedal is depressed, and can see fluid moving in and out of the master when bench bleeding.
I have tried it both ways, depress pedal, open bleeder screw, close bleeder screw, release pedal. I have also tried "pumping up" the pedal and then releasing. This is where my knowledge of what should happen is lacking, when I pump the pedal (4-6 times), should the pedal get firm? Because in my case, it does not. It will get "firmer", but never firm.
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post #6 of 11 Old 03-21-2017, 07:19 AM
festerw
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Not sure if it's possible on a CJ but i know I've accidentally reversed the calipers on a TJ. Makes it impossible to get all the air out with the bleeders on the bottom.
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post #7 of 11 Old 03-21-2017, 08:03 AM
hickslawns
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Should feel a little more firm each time you bleed a wheel.

I have a clear hose I put over the bleeder to watch fluid exit. Have you done this or how are you watching the fluid exit?

You might check that seal in the master to ensure it is properly seated. Or just check the drivers side floor. If it is leaking due to the seal, you will likely have some fluid on the floor and firewall.
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post #8 of 11 Old 03-21-2017, 08:29 AM Thread Starter
jackler
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Quote:
Originally Posted by festerw View Post
Not sure if it's possible on a CJ but i know I've accidentally reversed the calipers on a TJ. Makes it impossible to get all the air out with the bleeders on the bottom.
I checked this as well and fortunately the calipers are in the correct position with the bleeder screws up high
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post #9 of 11 Old 03-21-2017, 09:00 AM Thread Starter
jackler
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Quote:
Originally Posted by hickslawns View Post
Should feel a little more firm each time you bleed a wheel.

I have a clear hose I put over the bleeder to watch fluid exit. Have you done this or how are you watching the fluid exit?

You might check that seal in the master to ensure it is properly seated. Or just check the drivers side floor. If it is leaking due to the seal, you will likely have some fluid on the floor and firewall.
What I have been doing is using a clear length of hose attached to the bleeder screw, the other end in a Gatorade bottle with brake fluid in it, making sure the hose is below the fluid level. Then I watch the hose for fluid and watch for air bubbles in the bottle. I am having no problem getting the fluid to move through the lines and into the bottle, but it is always accompanied by air.

I did check for a leak at the master (as well as all brake line/hose connections) and have found no leaks.
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post #10 of 11 Old 03-21-2017, 09:13 AM
hickslawns
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Sure sounds like you are doing it right. Hmm. . . Now it is looking for tiny oddities. Maybe a pinhole leak in a line? Maybe a fitting sucking air? Maybe just a good air pocket that will let loose and you will suddenly have them bled in no time.
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post #11 of 11 Old 03-21-2017, 10:56 AM Thread Starter
jackler
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Quote:
Originally Posted by hickslawns View Post
Sure sounds like you are doing it right. Hmm. . . Now it is looking for tiny oddities. Maybe a pinhole leak in a line? Maybe a fitting sucking air? Maybe just a good air pocket that will let loose and you will suddenly have them bled in no time.
The former is what I'm working on now, the latter is what I am hoping for!! Would it be possible that air to return to the line through the bleeder screw? I was thinking maybe getting some speed bleeder screws?
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