On my 94 idi turbo there is a rear disc brake conversion. It's awesome untill my calipers went so I replaced both rear calipers and pads then I bleed the brakes and now no pedal. I've changed the master cylinder and the brake booster and bleed all of the brakes lord knows how many times. I've gone through a gallon of brake fluid bleeding. still no pedal. Could this be the proportioning valve? That's the only thing left I haven't changed. Also when I bleed the rear calipers the fluid comes out a little stream but the pedal does not go to the floor ? Only when the fronts are bleed it does. Little pressure being applied to the rear.. And yes I've made sure there are absolutely no leaky lines. Any help will be more than appreciated. Thanks

 

did you adjust the plunger rod when you changed the master cylinder, it has to be just right or it will cause problems, Proportioning valve is unlikely but possible, should be able to crawl under truck and have a buddy push on brakes, should be a little nipple on valve that moves when brakes are pushed, if the little nipple moves then the valve is good. dont know much about the rear disk conversions, but might have to pump it quite a while to get the rear break callipers to tighten up against the rotor like they need to.

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does the peddle fall to the floor, or is it very hard to push?

 

No I didn't adjust the rod do your mean the rod coming out of the booster tht pushes into the master cylinder ? And how do you adjust it ? And the proportion valve has a nipple to bleed it but that's the only nipple it has on it and I have tryd bleeding it but nothing works. And the calipers on the rear are out they are touching the rotor

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And yes the pedal goes to the floor unless you pump it really fast it will get real hard then just fade and I know it sounds like air but I just can't get any more air out of the lines ?

 

yes, i mean the rod that comes out of the booster and engages the master cylinder, sounds like it might be to short, there is a tool for adjusting it to the right length, but i just turn it out until it wont let the MC go all the way on without pushing the rod, then i turn it in to where it will just go on flush and just touch the rod. that should get you really close. Had the same issue with one of my old trucks and that fixed it completly.

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I dont remember the Prop valve having a bleed nipple, i thought they just pushed the fluid through and bleed at the brakes, have to force the valve in the prop valve one way or the other to get the fluid to bleed to the correct set of brakes, (front or back). but i may be wrong, been a long time since i messed with one of them, just sounds to me like the plunger rod for the MC.

 

So I just twist the rod by hand and it will move in and out ? Do I have to use a special tool? Well ill try it and let you know how it turns out thanks

 

there should be a little "nipple" on the end of the rod that unscrews from the shaft to lengthen the rod out.