71 B Body Brake Issues

71 B Body Brake Issues - 07/30/13 02:47 PM

Hey guys i have been fighting with me front brakes on my 71 Super Bee eveytime i drive it (which isnt far because of the issue i have been having.

I bought a complete brake line setup so they are all new along with a front proportion valve. My front disc brakes seem to lock up on me everytime i drive. I am not sure if its the calipers or the prop valve. 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?

I was thinking of finding an original front prop valve but didnt know if it could be a possible caliper issue as they were used. But they do retract when you crack bleed valve?

THanks,

Steve

Posted By: moparmarks

Re: 71 B Body Brake Issues - 07/30/13 03:45 PM

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.

Posted By: HemiChallenger

Re: 71 B Body Brake Issues - 07/30/13 09:17 PM

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

Posted By: 71birdJ68

Re: 71 B Body Brake Issues - 07/31/13 12:05 AM

Who did you get the valve from? I'm asking cause I bought all my stuff from the right stuff, and well its really the wrong stuff.

Posted By: Lefty

Re: 71 B Body Brake Issues - 07/31/13 12:25 AM

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?

Posted By: moparmarks

Re: 71 B Body Brake Issues - 07/31/13 12:41 AM

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.

Posted By: THESHAKERPROJECT

Re: 71 B Body Brake Issues - 07/31/13 05:45 PM

The first run of the repoped prop valves were defective and I had the same issue with my 71 Charger RT. The problem is the top piston letting fluid travel one way to the calipers but not back to the master when you release the brakes. You may be able to search my prev post a few years ago about this issue. The simple fix is to replace the upper piston with one from a oem valve. My valve worked perfectly when I did this. I notified some of the suppliers of the defect but I saw many at Carlisle selling the defective valves the same summer.

Posted By: HemiChallenger

Re: 71 B Body Brake Issues - 07/31/13 09:13 PM

Thanks for the replies. I bought one two to three years ago and had the problem. Then i bought one last year and im still having the problem. I got it from FINE LINES. My rubber hoses were originals i got from a car with low miles that was wrecked in a roll over. I drove the car again and it locked up again. I didnt touch the thing and after about two hours the the brakes came undone. Maybe a slow release or poor spring on the piston? Im getting annoyed as i just want to drive the car without a problem for once!

Steve

Posted By: therocks

Re: 71 B Body Brake Issues - 07/31/13 09:34 PM

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

Posted By: steve70

Re: 71 B Body Brake Issues - 07/31/13 09:44 PM

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.

Posted By: screamindriver

Re: 71 B Body Brake Issues - 08/01/13 02:20 AM

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...