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Old 11-01-2019, 08:47 AM   #1
usered
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Default Brakes

I'm putting 39 -48 hydraulic brakes on my model A frame and have a couple of problems that hope someone maybe able to help we with.

Configuration:
I have a single wilwood master cylinder with 1" piston mounted to the transmission below the floor boards. I've run 3/16 brakes lines from the Master first into a residual valve 10psi then into a "t" one line going to the rear and front to the front.
The pedal ratio is 6.5 to 1. There are no leaks of fluid anywhere I can detect.
I should mention all parts are new.

1st problem is I can bleed the brakes getting fluid out of each wheel cylinder. The pedal at this point as pressure but is soft. The brakes work. If I let it set over night and then depress pedal it goes all the way to the floor, no brakes.

The second problem is when I have some brake pressure if I depress the pedal and hold pressure on it for a few minutes (checking for leaks) the two front wheel cylinders leak fluid around the rubber seals. Again these are new 1 1/4 wheel cylinders. The pedal will eventually go to the floor, no brakes.

Open to any ideas as to what the problem could be.
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Old 11-01-2019, 09:04 AM   #2
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Default Re: Brakes

There was a post here on the Barn about some aftermarket wheel cylinders having a steel sleeve that leaks/moves in the bore. Might check for that. I assume your brakes are adjusted correctly. Also.. 1 1/4 wheel cylinders? Seems awful big for a 1" master cylinder.
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Old 11-01-2019, 10:29 AM   #3
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Default Re: Brakes

Tommy, tanks for some feedback.

I have 1 1/4 on the front and 1 1/8 on the rear I think got them from Mac's they didn't specify what the size was. What do you think they should be??

As to the sleeves are they all steal?
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Old 11-01-2019, 12:52 PM   #4
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Default Re: Brakes

There have been a lot of reported issues with the import brake parts, especially the wheel cylinders. Some have the holes drilled incorrectly as well. You probably don't want to hear this, but I would look for some U.S. made wheel cylinders. I purchased some from Rock Auto a few years back, but they may be gone. You could check with the suppliers that are here on the Barn that sell NOS and U.S. manufactured parts.
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Old 11-01-2019, 02:27 PM   #5
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Default Re: Brakes

Leaking wheel cylinders is certainly part of your problem. Get those replaced as a first step. Getting to a firm pedal requires a sound fluid system.
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Old 11-02-2019, 08:52 AM   #6
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Default Re: Brakes

If you can't find locate good wheel cylinders; you can address the miss-drilled holes by milling the slot in the large piston a little deeper, 1/8" works. This lets the cup sit clear of the hole. You can use a cut-off wheel to "mill" the slot.

1/4" lines would be a better choice with early Ford Lockheed brakes.
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Old 11-02-2019, 06:49 PM   #7
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Default Re: Brakes

Thanks all for the feed back, given me a few things to try.
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