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Front brakes not working
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57Groucho
Posted 2019-06-16 11:36 PM (#583549)
Subject: Front brakes not working



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Location: Minneapolis
I swapped in dual reservoir master cylinder in my 57 Fireflite, I also put in all new lines and wheel cylinders. I did bench bleed the master, I've got no leaks and all the air is out of the system as far as I can tell, there's no more coming out of any of the bleeders anyway.
The stream of fluid is nice and strong coming out of the bleeders when I crack them but the front brakes aren't working and the pedal goes pretty much straight to the floor. The rear brakes seem to be working fine, I can't turn them by hand anyway. I've got the pushrod adjusted to the factory spec and the shoes are adjusted correctly, I'm kind of at a loss. The master cylinder is for a 67 B/C body with power drum brakes and they're cheap Chinese wheel cylinders. I'm thinking it's something with bleeding the dual wheel cylinder setup because it's acting like there's still air in the system. Hopefully it's something simple that I've overlooked. Here's some pictures of what I'm working with. Any help would be appreciated.

-Dan

Edited by 57Groucho 2019-06-17 12:19 AM




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Coronet_Jeff
Posted 2019-06-19 8:34 PM (#583743 - in reply to #583549)
Subject: Re: Front brakes not working


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My first thought is that the 1967 m/c doesn't move enough volume up front to actuate both wheel cylinders. Perhaps a disc/drum m/c would push enough volume for the dual cylinder setup?
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58coupe
Posted 2019-06-20 10:26 AM (#583764 - in reply to #583549)
Subject: Re: Front brakes not working



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describe how you bled the master cylinder. Did you bleed it on the bench before installing it? The best way to do this is with short pieces of tubing bent to to flow back into the top of the reservoir and with the MC clamped in a vise. Pump it until you are sure all the air is out. I have had air trapped in the forward side of the MC even though it appeared to be bled.
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57Groucho
Posted 2019-06-20 10:37 AM (#583765 - in reply to #583549)
Subject: Re: Front brakes not working



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That is exactly how I bled the master cylinder. At this point I'm thinking the master might be bad. It certainly wouldn't be the first time I've had bad parts straight out of the box. I'll try putting another one in this weekend if I have time and let you guys know if that works. It's Back to the Fifties this weekend though so I might not have time. Thanks for your input.

- Dan
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wizard
Posted 2019-06-20 10:51 AM (#583769 - in reply to #583549)
Subject: Re: Front brakes not working



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Brakes are not rocket science - I've never bench-bleed any m/c and never had any problems getting the air out.

My guess is that the displacement is too low in m/c for the front brakes.


Try to adjust the front brakes to full Contact and see if you can get some resistance in the pedal.
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57Groucho
Posted 2019-06-20 11:54 AM (#583774 - in reply to #583549)
Subject: Re: Front brakes not working



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That was my thought too, they're very simple, they should work. I have already adjusted them to full contact, no luck. Maybe you guys after right about the master.
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57chizler
Posted 2019-06-20 12:43 PM (#583779 - in reply to #583549)
Subject: RE: Front brakes not working



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Did you plumb the rear MC outlet to the front brakes like the factory did? Are you sure of the pushrod adjustment i.e. there is free play in the pedal before the pushrod contacts the MC piston?

Like Jeff said, the 1" MC bore might simply be too small for your system, original was 1 1/8".
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57Groucho
Posted 2019-06-20 12:52 PM (#583780 - in reply to #583549)
Subject: Re: Front brakes not working



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I did not plumb the rear outlet to the front. I figured the larger of the two outlets would be the front, also, it's in the front. Maybe a big mistake?... I'm pretty sure that the freeplay is right...

Is there a fish reservoir master cylinder with a 1 1/8 bore?
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57Groucho
Posted 2019-06-20 12:56 PM (#583782 - in reply to #583549)
Subject: Re: Front brakes not working



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fish reservoir master cylinder = dual reservoir master cylinder
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Powerflite
Posted 2019-06-20 3:41 PM (#583788 - in reply to #583549)
Subject: Re: Front brakes not working



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I must confess that I don't know if it would make any difference swapping front to back on a drum/drum master. If the reservoirs are equally sized, I don't think it would matter, but there may be some other reason not to do it like some internal proportioning system. The best way to troubleshoot is to start eliminating the possibilities before you go changing parts around. Take a hose clamper and clamp one front hose at a time to isolate that wheel and see if it makes a difference to the pedal. Make sure the edges of the clamp are rounded so you don't damage the hose. After you clamp a line and the pedal is magically fixed, you know that the problem isn't in the master and is present in that one wheel. If you end up clamping all the hoses and it still isn't fixed, you know that the problem is either in the lines or in the master.

One thing I don't like about your system are the use of those plugs in your distribution block. I have had terrible luck with them leaking. But others have gotten away with them, so they might be OK.
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1960fury
Posted 2019-06-20 4:37 PM (#583795 - in reply to #583780)
Subject: Re: Front brakes not working



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57Groucho - 2019-06-20 12:52 PM

I did not plumb the rear outlet to the front. I figured the larger of the two outlets would be the front, also, it's in the front. Maybe a big mistake?...


Of course not, you did it right.
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57Groucho
Posted 2019-06-20 5:59 PM (#583805 - in reply to #583549)
Subject: Re: Front brakes not working



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I like the hose clamper idea, I'll try that. As for the plugs in the distribution blocks, I couldn't find any replacement blocks that would distribute the lines like I wanted. Hopefully they'll work ok for me.
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57Groucho
Posted 2019-06-20 6:01 PM (#583806 - in reply to #583795)
Subject: Re: Front brakes not working



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1960fury - 2019-06-20 3:37 PM

57Groucho - 2019-06-20 12:52 PM

I did not plumb the rear outlet to the front. I figured the larger of the two outlets would be the front, also, it's in the front. Maybe a big mistake?...


Of course not, you did it right.


That's good to know. I didn't see how it would make sense the other way.
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