The Stovebolt Site Forums The Shop Area Engine Shop brake adjustment question

I am in the final phase of completing my brakes (56 3/4 ton). EVERYTHING is new except a rebuilt master cyl.

No leaks, but sadly not much pressure either. I have done all the brake, 2 person, pump the pedal, bleed the brake, items etc.
I dont really get any gravity bleed at the rear wheels.

So heres my question before I bite the bullet and figure the master cylinder rebuild didnt work, and I lose my built up pressure here.

Is is possible since I have not adjusted the brake shoes to the wheels yet through the slot in the rear of the wheels, could the new wheel cylinders pistons be pressed out to far in the wheel cylinders and this is where I am losing air pressure?

I am really confused becuase I do not see fluid anywhere. I am thinking w/ any pressure at all, I would eventually lose fluid too. Wondered about the master cylinder cap too, with that little bit of air, maybe it leaks here???
Thanks you any advise.

I never build enough pressure at the farthest wheel to quirt fluid. the front cylinders shoot 2 feet!

Hy 56 stepside, did you bench bleed your rebuilt master cylinder before you installed it? You have to adjust your brake shoes up to proper clearance to achieve any pressure, otherwise the shoes have nothing to press against, and hence no pressure on the pedal. Incidently we don't want any air in the hydraulic brake system, that is what you are trying to remove in the bleeding process, air can be compressed, liquids cannot, so if you have air in your system it will compress before the brakes can apply, resulting in a spongy or no pressure pedal. You said everything was new, does that include your steel brake tubing and the three flex lines in the system?

hi 3b,
yes everything is new except the MS is it rebuilt. I did not bench bleed. I have not adjusted my shoes. I know no air should be in there. I didnt really know what goes on under the cap in the MS when its screwed on, I thought some ait might be in there at the top.
sounds like before I give up on the MS rebuild, I should bench test it, adjust the shoes and give it another shot. I have no flex lines, jsut steel lines.

56 stepside,

You are right, if a wheel cylinder blew its piston out, you would see brake fluid cascading out of the backing plate area.

I wouldn't do anything until I adjusted all four wheels up dead tight, then back each of 6 clicks or so. Adjusting them up fully is critical, it centers them and gets everything on an even keel.

After you have done this, start your bleeding procedure at the wheel cylinder farthest from the master cylinder.

With two people, pump-pump-pump and hold, then crack the wheel cylinder. Don't allow the master cylinder to run dry.

Do each wheel until the big burps and bubbles stop coming out. I'll bet you have super hard pedal before you know it.

EDIT. IMHO, there is no need to bench bleed the master cylinder. Nothing happens on the bench that doesn't happen when it's bolted to the vehicle.

Stuart

You mentioned that you don't have any flex lines, just steel lines. You should have 3 flex (rubber) brake lines - one to each front wheel, and one to the rear axle. If you have steel lines instead of flexible line in those places, the steel lines will break as soon as you go over some bumps.
Samantha

Thanks Stuart, will do and yes i do have rubber lines to the wheels not solid ones.

56,
Just a ? ..did you replace the rubber flex line at the rear with a new one ?
Just asking because when I redid my system my flex line looked great on the outside no dry cracks or nothing so I reused it but internally it was shot and caused me MANY HRS. of frustration when I tried to bleed the system, internally it had rotted and plugged up and would not let me get any pressure, after replacing it the Rear brakes darn near gravity bled themself.

Tim

good call I will try it

Thefluid you see in the master cyl under the cap is in the resorvoir. It will naturally have air above it. Just dont let the level get below the bottom or you will have to start over. Its a good idea to bench bleed a master cyl. but you have gone this far it is not nessesary now. Adjust them like the guys said & if you still dont get pressure to the rear wheels you have a blockage like they describe. I believe you are getting close.