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Brake Bleeding Problems..

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Old Jul 20, 2008 | 09:15 PM
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Default Brake Bleeding Problems..

Working on a friends 81 that had a leaking rear driver side caliper... Well I have been trying like hell to get the damn things bled but just can not get the peddle to stiffin up... Here is how I am going about things tell me if I am doing something wrong... First I filled the master cylinder up second i cracked the bleeder open and then used the vacuum pump I bought from autozone I would pump til the little container on it was about half full close the bleeder with it still attached empty the container refill the cylinder and then do the same thing with the bleeder on the other side of the caliper... Continued this process 5 times and the peddle still goes clear to the floor... Now if you take the car out on the street depress the brake peddle clear to the floor the front brakes will hold the car in place and burn the tires but the rear rotors remain cold so what am I doing wrong with getting the air out of the rear brakes??
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Old Jul 20, 2008 | 09:26 PM
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I also use a vacuum bleeder that I bought at Autozone. Mine has a vacuum gauge attached. I connect the hose to the bleeder screw, pump until I get a good vacuum, then open the bleeder screw and close it before the vacuum gets to zero. I continue doing this until I'm satisfied that all the air is out of the system, making sure the master cylinder is filled with brake fluid.
I'm not saying that my way is the right way, but my brake pedal is full and hard.

Last edited by 71 Green 454; Jul 20, 2008 at 09:28 PM.
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Old Jul 20, 2008 | 09:50 PM
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Sounds as if the proportioning/combination valve needs to be recentered. Upon initial failure the valve would have shifted internally. Is your dash brake warning light illuminated?
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Old Jul 20, 2008 | 10:15 PM
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I'm guessing the rear reservoir in the master cylinder went dry...did you bleed the master cylinder?
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Old Jul 20, 2008 | 11:31 PM
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Did you prime the master cylinder? Also did you ever pump up the brakes before bleeding originally? May need to see if it will pump up before doing any bleeding. May have a master cylinder problem if you can't pump it up.
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Old Jul 21, 2008 | 06:30 AM
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bleed master cylinder first
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Old Jul 21, 2008 | 01:06 PM
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Originally Posted by slk230red
I also use a vacuum bleeder that I bought at Autozone. Mine has a vacuum gauge attached. I connect the hose to the bleeder screw, pump until I get a good vacuum, then open the bleeder screw and close it before the vacuum gets to zero. I continue doing this until I'm satisfied that all the air is out of the system, making sure the master cylinder is filled with brake fluid.
I'm not saying that my way is the right way, but my brake pedal is full and hard.
This way works great. Like he mentions, you already need to be pulling about 15psi in the pump before you crack the bleeder and make sure you close it as it reaches 0psi. Repump to 15psi and repeat. Don't let the MC go dry!

Having said all of that, if you never get a firm pedal I would suspect your MC went bad. Mine did the same thing last month when I was working on my calipers. Too much bleeding can lead to an old MC going bad - even if that wasn't originally the problem. I replaced mine and the problem was solved!
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Old Jul 23, 2008 | 11:10 AM
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how do you bleed the master cylinder... and yes the brakes will pump up..
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Old Jul 23, 2008 | 01:20 PM
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Originally Posted by Dante7
how do you bleed the master cylinder... and yes the brakes will pump up..
Here's a paper on the subject to help you. There should have been instructions with the m/c and the tools to bench bleed it.

http://www.superchevy.com/technical/...nch/index.html
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Old Jul 23, 2008 | 04:54 PM
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Originally Posted by Jud Chapin
Here's a paper on the subject to help you. There should have been instructions with the m/c and the tools to bench bleed it.

http://www.superchevy.com/technical/...nch/index.html
Neat article. Short and to the point. The idea of installing the M/C to get the other components aligned and then removing it to bench bleed is a good one for newly installed systems.
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Old Jul 23, 2008 | 04:58 PM
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Originally Posted by CA-Legal-Vette
Neat article. Short and to the point. The idea of installing the M/C to get the other components aligned and then removing it to bench bleed is a good one for newly installed systems.
Yes, About the best one I ever seen on the subject. I put it in my vault of articles.
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Old Jul 23, 2008 | 07:30 PM
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Also, get a motive brake bleeder. You'll never look back.

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Old Jul 23, 2008 | 07:38 PM
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I like the good old fashioned way ......... the missus sitting in the car, me yelling out pump 6 times, hold, pump again etc. etc. That way I get to see the bubbles in the clear plastic tube & know when to stop.
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Old Jul 23, 2008 | 08:40 PM
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That was a good link to the article. It doesnt matter how good you bleed the brakes if you have air trapped in the master cylinder.

Will continuing to bleed the brakes eventually get the air out of the master cylinder?

kdf
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Old Jul 23, 2008 | 09:06 PM
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Originally Posted by kdf1986
That was a good link to the article. It doesnt matter how good you bleed the brakes if you have air trapped in the master cylinder.

Will continuing to bleed the brakes eventually get the air out of the master cylinder?

kdf
Possibly, but it would take a lot of bleeding. The M/C has a lot of air in it when dry and all that air would have to be pumped through the entire system.
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