Brakes

usered

usered

Senior Member
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.
 
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.
 
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?
 
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.
 
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.
 
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.
 
You must log in or register to reply here.
Back
Top