The Stovebolt Site Forums The Parking Lot Big Bolts Master cylinder reassembly

Working on my 59 2.5 ton master cylinder. I have reassembled it and i was pumping it to bleed it. I got no fluid out the end. This has me questioning my reassembly order. I have a picture but am not at a computer right now so I can't upload it. Maybe some one here can tell me if I have it right base on my description. This is a 1.5 inch bore.
The Order the parts came out ( starting at the pedal end)
Push rod and end cover
Piston ( rubber gasket end has divot to receive the push rod next to push rod)
Brass washer
Cup (cupped side over the spring flat side against the flat end of piston
Then the last thing is the spring

This order of assembly seems like the brass washer would prevent fluid passing through the small holes on the flat end of the piston. Maybe I don't know how to bleed it properly

Anyway a picture is worth more than all these words so let me know if it is necessary
GJ

Photo link (I hope)

[IMG]http://i408.photobucket.com/albums/pp165/datagirl79/Mobile%20Uploads/image.jpg[/IMG]

Hy Gene_Spartan80, your assembly order sounds correct, did you disassemble/clean the end nut which contains the residual pressure valve? Are your intake and bypass ports inside the master cylinder bore clean?

I cleaned the large nut on the end. you mentioned a residual pressure valve inside it? I could see straight through it but i did not see anyway to break it down further. Both ports in the reservoir are clear.

These brakes are driving me crazy. there is a fluid at the back end, where the boot is. I am waiting on the master cylinder kit to arrive and the drip is only slight and i believe i should be able to bleed the brakes and see if all the other work i have done has accomplished anything.

so far i have honed the master, reassembled it, new hydrovac, new wheel cylinders up front, rebuilt back wheel cylinders, new hoses (all 3). at this point i think bleeding properly is the only thing that i need. The only thing left of the original is the fittings and steel line. I have a good flow of clean fluid at each bleeder but the air never seems to stop coming out of the bleeders, all 8 of them.

i have tried pressure bleeding and manual pumping with 2 people and neither seems to be working.

BTW, i can't seem to find a replacement master cylinder for this. I can find one that looks exactly like it but i am not sure of its bore size. Its NAPA part number is NMC P21698. They have it listed for 1 1/2 ton trucks they don't have any listed for 2 1/2 tons. My master cylinder bore is 1 1/2", raybestos 21698 has 1 1/4" bore but looks right.

NMC P21698..... I think is a 1 1/4" bore.

It seems there should be a check valve that goes on the back end of the spring. Then there is a rubber washer against the big nut at the rear. Did you bleed the booster also?

Gene,

If I remember correctly the check valve snaps into the end of the spring and would be located at the outlet end (don't see it in the picture)...is it there?

I also don't remember the brass washer in that location, but it's been a while since I've been inside a MC...might have a junk one laying around that I can knock apart, I'll look tomorrow.

Also, you've done all this work, why not replace the steel lines as well? They fail from the inside out...just a thought.

Mike B

This cylinder did not have a check valve or washer. I did bleed the booster. The rear brakes showed a little movement at first but the more I bled the wheel cylinders the less pedal I felt.

I think I will plug the master cylinder and see if I have pedal then if I do then I will go back to work bleeding the system. If I dont have pedal after plugging I will wait until my rebuild kit arrives. Btw, does it matter is the cap is tight on the reservoir during bleeding I have tried it both ways. A few times with the cap off fluid shot up out of the reservoir when the pedal was released.

Does this mean you are using the original parts? That may be the problem. Ive never seen a single MC without the check valve. Maybe the kit will have one in it. Like 3B says make sure the ports are open. One is a very small hole. Poke a tag wire through it to open it up.