Re: 71 B Body Brake Issues
[Re: HemiChallenger]
#1476419
07/30/13 11:45 AM
07/30/13 11:45 AM
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Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
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Hey Steve.
I've had this problem on a couple 71's and it was the valve not releasing the pressure. Lock up the brakes like it is doing and then pull the little bypass pin on the valve and see if they release.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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Re: 71 B Body Brake Issues
[Re: HemiChallenger]
#1476422
07/30/13 08:25 PM
07/30/13 08:25 PM
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Joined: Sep 2005
Posts: 6,516
Santa Cruz, California
Lefty
master
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master
Joined: Sep 2005
Posts: 6,516
Santa Cruz, California
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Quote:
If i crack the bleeders on the front i can then push the car then re bleed them and it works fine for a short time until it does it again. What would you suggest i do?
That tells you the master cylinder or prop valve is not releasing brake line pressure. It's usually caused by incorrect pedal to MC push rod adjustment or MC to booster push rod adjustment.
Make sure you have a little play in the brake pedal before it pushes the piston in the master cylinder. Same for the MC to booster if you have one.
If you have not done anything to the MC or booster that could have changed the gaps, it's probably a bad prop valve ,MC or clogged brake lines. How old are the flex lines to the calipers?
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Re: 71 B Body Brake Issues
[Re: HemiChallenger]
#1476423
07/30/13 08:41 PM
07/30/13 08:41 PM
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Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
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Quote:
Mark i tried this and it worked. BUT that being said it does this quite frequently, is there a solution to the problem? Ive heard of this problem with these prop valves and i really dont want to have to do this all the time. Is there a fix or should i just hunt an original?
Steve 
If it releases with the bypass pin then its probably the valve.
My issues were with original valves, not repros. I just took the valve apart and cleaned it up real good and then they worked fine.
Probably have had around 5 71B/E disc brake valves do this.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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Re: 71 B Body Brake Issues
[Re: HemiChallenger]
#1476426
07/31/13 05:34 PM
07/31/13 05:34 PM
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Joined: Jan 2003
Posts: 21,072
Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,072
Niles , Ohio
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So you used old used hoses?That makes no sense.No matter the mileage they can be swelled inside.Aside from that Id guess PP valve.I run one from a 5th Ave on my 65 disc conversion.Been on at least 12 years and no problems.Rocky
Chrysler Firepower
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Re: 71 B Body Brake Issues
[Re: therocks]
#1476427
07/31/13 05:44 PM
07/31/13 05:44 PM
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Joined: Dec 2011
Posts: 892
MA
steve70
super stock
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super stock
Joined: Dec 2011
Posts: 892
MA
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I'd start with the brake hose. I've seen a few collapse and cause the same issue. They're cheap and easy to change.
1970 Challenger T/A 4 speed
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Re: 71 B Body Brake Issues
[Re: Lefty]
#1476428
07/31/13 10:20 PM
07/31/13 10:20 PM
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Joined: Feb 2004
Posts: 7,196
Harrisburg, Pa.
screamindriver
master
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master
Joined: Feb 2004
Posts: 7,196
Harrisburg, Pa.
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Quote:
Quote:
If i crack the bleeders on the front i can then push the car then re bleed them and it works fine for a short time until it does it again. What would you suggest i do?
That tells you the master cylinder or prop valve is not releasing brake line pressure. It's usually caused by incorrect pedal to MC push rod adjustment or MC to booster push rod adjustment.
Make sure you have a little play in the brake pedal before it pushes the piston in the master cylinder. Same for the MC to booster if you have one.
If you have not done anything to the MC or booster that could have changed the gaps, it's probably a bad prop valve ,MC or clogged brake lines. How old are the flex lines to the calipers?
If you're looking past the prop valve take this posted advice and confirm the pushrod legnth as the second thing to do...If the pressure released at the pin then the hoses are'nt the problem...Would I run the old hoses ??? Absolutely not but the pressure would be from the hoses out {at the caliper} not all the way back to the prop valve... My guess is the prop valve as other have suggested... 
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