Master Cylinder Rebuilding Question

[John Kuzman]

Greetings!
I have two questions as I am rebuilding my dual Master Cylinder for a '59 Bugeye.
1. There is a black washer that came with the kit that is about 1/8" thick with an outside diameter the same as the cylinder bore. I did not remove a similar object during the teardown. Does this washer go into the brake cylinder as the very first piece? When I disassembled the brake side, the last piece to come out was the spring that had the metal cup with a rubber insert.
2. Is it absolutely necessary to bench bleed the MC, or can I install it dry and get a good bleed using my pressure bleeder. If I must bench bleed, what size are the outlets? Can I just screw in some bleeder screws?
As always, thanks for any, and all advice.
John

 

[mailbox]

Bench bleeding is not required, but will make it much eaiser to bleed when you install it on the car. The best method of bench bleeding I have seen is to attach 2 short brake lines to the MC, bend the tubes around until they are in the reservior, fill the resevior with brake fluid, insert a large screwdriver in the back of the MC and push all the way in. Do this until no air comes out of the brake lines. I would still pressure bleed the car afterwards. I can't help you with the 1st question. Sorry. /ubbthreads/images/graemlins/frown.gif

 

[spritenut]

John

That thick rubber washer is the brake proportioning valve or some sort of brake valve. It is the first piece in the brake side bore of the master. That is the first piece to go in, all the way in the back of the bore. Do make sure the old one is out. Most of the time they have turned to a black goo but they are still stuck in the bore way back there.
Also be careful on which bore is what. You are working on it reversed and it's real easy to stick that washer in the clutch side.

Bench bleeding is not neccessary, but as Mailbox explained, it sure helps. I do the 2 short lines back into the master aswell. Just pump til there are no more visible bubbles.

Frank

 

[John Kuzman]

Mailbox and Frank,

Thanks for the advice. I will bench bleed in the vice. Frank: Thanks for clarifying the washer. I think that if there was one in there, it was the black crud and sludge I saw when I blasted some brake cleaner in the bore and hit it with compressed air.

John