brakes wont work

[fredscarryall]

i have a 1950 suburban with an aftermarket firewall mount power booster, 1970 chev truck master cylinder,1978 ford granda new front disc brake setup the came with my ifs, used 1994 lincoln mark 8 rear with discs brake set up (disc where resurfaced and new pads),and a new aftermaket disc/disc portion valve mounted on the frame. i have gone through my forth master cylinder and the brakes wont bleed and i cant get a pedal. the last master cylinder bench bled perfectly on the bench but as soon as i get the lines hooked up it doesnt bleed. i have power bled, open up the bleeder and tried to let it bleed on it own, and ran a tube from the bleeder to a bottle filled halfway with fluid and pumped the pedal. nothing happens. what could be the problem? i think we have spent about 6 hour trying everthing. there are no leaks anywhere. anybody ever have this problem.

[chev3600]

When you push the pedal, nothing happens? No air or fluid flow? Is the pushrod at fhe pedal correct? On some headaches, I will use an older style oil squirter bottle filled with brake fluid and force the fluid and air back up from the bleeder to the master. Good luck, you'll get it working.
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[fredscarryall]

i bench bled the master on a bench and just in case i kept the bleeding kit hooked up and bled the master cylinder again on the firewall hooked up to the brake pedal. both way the master cylinder bled perfectly. when i hook the line to the master and push the pedel in and release, fluid does flow up in the master cylinder (looks like a little one inch fountain)and sometimes a get an occasional bubble.i will try blowing air up the bleeder.does anyone else have something i can try or look for.

[OrrieG]

Start with the basics. Does the pedal move the MC rod far enough to move fluid? Crack the lines out of the MC, does fluid squirt out when you push the pedal? NO, then something is haywire in the mc or linkage. YES then move to the next joint at the proportioning valve. Fluid at the valve outlets when you push the pedal? NO then the proportioning valve may need centered or ?? This usually only affects the front or back. YES move on down the lines to the calipers. If your proportioning valve is lower than the calipers (usually the case with lowered rigs) you will need check valves in the lines to keep pressure to the calipers. Check for fluid into the calipers, then at the bleeders. Speed bleeders are a big help. I have never used a power bleeder, just the pump it a hundred times method. Speed bleeders allow one person to open the valve and pump, they have a built in check valve. It took me two weekends and probably 8 hours before I figured out I was trapping air in an expansion loop I had put in my lines. Also, I don't know about Ford calipers but GM can be swapped side for side which puts the bleeder on the bottom and traps air in the top of the caliper ( fought that one on my kids truck when she was given the wrong caliper by a parts person). Make sure your bleeders are on the top of the calipers, you want the trapped air to rise up to the bleeder, it will not get forced to the bottom with pressure. Also check to make sure you do not have any vertical loops or places in your lines that can trap air. Good luck, bleeding brakes is not one of my favorite things to do, but I HAVE had lots of experience!

[dwcsr]

Make sure the prop valve is centered.

[fredscarryall]

thanks for the help. i started with the basics and went through everything one more time. it end up being that the front caliper where on the wrong sides. as soon as my friend switched them and the bleeders where on the top of the calipers. the brakes bled good and i got a brake pedal back.