My son and I installed a disc brake conversion kit and bled the brakes after we replaced the hard lines. It bled fine then but still has a soft pedal. Yesterday I removed the mc from the booster to level it to get any air trapped there yet. we tried gravity bleeding the rear brakes and nothing came out. the bleeder screw was almost out, that's how open it was. When that did'nt work I filled the mc all the way before reinstalling it and tried pedal bleeding. Nothing. I pumped up the pedal, held and Mike cracked open the bleederand nothing came out again. we didn't try the front brakes yet.
Any ideas? the mc has bleeders on it. I didn't open them when gravity bled because I had the topp off the mc.:sad:

I've had this problem getting the master cylinder to start working. Put a bunch of towels to catch the splash, hook up a hose to the MC bleed valve like a wiper width hose, and route it back into the MC. Loosen the screw and then pump the pedal until you get fluid going through it back into the MC. Then you can bleed your rear lines.

thanks I'll try that

What year is the car? Is there a hold off valve on the rear cross member?

If the push rod between the power booster and the master cylinder is to long it will not allow the piston in the master to return completely. Try loosening the bolts that hold the master cylinder to the power booster and bleeding the system.

I bled the system when we installed it this past winter. the pedal is a little soft yet. that is when we pulled the MC off the booster. we were told there might be a bubble in the mc yet so we leveled the mc and tried to gravity bleed, nothing. so I reinstalled the mc on the booster and tried pumping up the pressure and still nothing. I'm going to try using the mc bleeders.

ok i did my novas brakes a while back and the rear brakes were completely dry of any fluid so the proportioning valve got stuck so it only actuated the front brakes. i would only get a small trickle out the rear bleeders and it would periodically pop out some air, no pressure at all. so what i had to do was bleed the fronts and you will hear a pop (well with me it was loud so it should be noticed) and then you can bleed the rears. so bleed front till you hear a pop, i would do both sides just incase and then bleed the rears. if the pedal feels good take it for a short test drive!!

Your combination valve has a neat safety feature. If you loose pressure, say to the rear brakes, a piston moves and blocks the rear brakes off and then the fronts keep working. To get the piston to recenter, open up the front brake lines with the backs closed and step on the brake pedal sharply. I had to do this on mine when I rebuilt the whole system.

thanks. I didn't here anything like that before. I'll try that.