4 wheel disk brake bleeding issue

put 4 wheel disk brakes on the car and am ready to junk the whole car.

4 Days now working on the brakes and still no brakes. Well I do have some fronts buy nothing in the back.

I used a late 60's corvette masrter (4 wheel disk), standard disk from a nova on the front and GM metric on the back. Well as some of you alrady know I am having problems. I can not get a good pedal in the back. The brakes will push out fluid if you try to bleed them but the pedal will not go down. It's like you not opening the line at all. The pedal feels soft not matter what you do, I have pulled the calipers off and made sure the bleeder is at the top, changed master cylinders and still the same issue. Proprotioning valve is disk/ disk not leaks.... WTH am I doing wrong.

Joe

If the pedal was going all the way down and you had fluid to the rear, I would say theres still air in the line. Being that the pedal will not go down, I'm thinking that there may be a blockage in the line somewhere. Maybe a small piece of debris thats allowing a little fluid by but not enough to apply pressure to the brakes. Check for a blockage. Maybe blow out the lines with air. Billy.

Open the line at the inlet side of the flex line at the differential and check for flow there. If ok then do it at the outlet side. This line can collapse internally and cause probelm, even if new. Catch the fluid so you can check for any debris flushing from the lines.

What GM car did the calipers come from? I am using 82 Cadillac Eldorado brakes and know the bleeding is going to be a PIA because the bleeder isn't all the way to the top. I am going to remove them from the mount, place a block between the pads, put the bleeder at the top and then bleed them. When the air is gone I'll install and adjust the pads out with the parking brake lever.

All of the above sounds like good advice but,have you thought about using an adjustable proportioning valve? Just a Thought.

Did you try gravity bleeding the brakes. I had the same problem on my 72 after a complete brake rebuild minus the hard lines. It took forever to get a pedal out of it.Also there is a unit but dont remember the name the bleeds off the system with assistance from compressed air and does the hole system from one bleeder screw. Hope this helps.
Greg

did you replace all of the brake lines? including the soft line at the rear. When I did my 4w disc swap that is what got me.
I ran all new hard lines and left the soft line and it
ended up taking a shat after about the 2nd brake
application I made. Also my brakes take 2 pumps to
get a hard pedal. I'm told this is normal so you wont get brake drag.

Did you bench bleed the master cylinder first!

If not this can cause major head aches!

this is a good instruction link

http://www.superchevy.com/technical/chassis/brakes/0509sc_bench/index.html

Try pinching off the rubber hoses and check if the pedal is firm. If it is release 1 hose at a time to determine which caliper is the problem. Do you have calipers with a built in parking brake? If so you will not get a good pedal until the parking brake is adjusted. If the pedal is still low with the hoses pinched off, plug the ports in the master cylinder. If the pedal is still low then the problem is in the master. If the pedal is firm, it is air in the lines.

http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm

Danny Nix
CPP

Are the bleeders on the rear brakes on the top? If not they should be.....

A few more thoughts; is the pushrod from the pedal to the m/c adjusted correctly; no preload with a slight bit of clearance between it and the cup of the m/c.
Do you have a factory style prop. valve; does it it have a small button/stem? If so you need to depress this while bleeding; will require a helper or some way to hold it in.