I need to stop......literally!

[mobileortho]

Still tinkering around with the rear end/disc brake swap for my truck. Finished up the emergency brakes recently and bled the brakes but I have no pedal pressure. I bled them twice now with no success. Any ideas on the cause?

[OrrieG]

Is the master cylinder on the firewall or low on the frame? If low you need the back flow resisters to hold the pressure in the lines. Is your proportioning valve working right? Is there any place in the lines that an air bubble could get trapped (high loop)? Do you know the MC was good (I'm on my third from not exercising them when sitting)? Are your calipers installed with the bleeder on the top (they will fit with the bleeder down on the opposite side trapping air in the top)? Except for the back flow I have had all of the other issues. It took me two weekends to get the air out of my system and find all the little problems.

[youngrodder]

How about the MC? Is it new or completly dry? I had to bench bleeded mine prior to bleeding the entire system. Just a guess..

Marc

[mobileortho]

I believe it's the mc. I'd used a vaccuum pump to bleed the lines. Had my son the pump the pedal last night while I checked the bleeder and got nothing. I had changed master cylinders right before I started the rear end swap. It's the same type I had before (corvette style) that I swapped ou because I came across this one that had a proportioning valve already attached. It's a new unit that I got from someone who had purchased, then went another route. Can't swap the proportioning valve to the old mc because they use different size lines.

[youngrodder]

Originally Posted by mobileortho

I believe it's the mc. I'd used a vaccuum pump to bleed the lines. Had my son the pump the pedal last night while I checked the bleeder and got nothing. I had changed master cylinders right before I started the rear end swap. It's the same type I had before (corvette style) that I swapped ou because I came across this one that had a proportioning valve already attached. It's a new unit that I got from someone who had purchased, then went another route. Can't swap the proportioning valve to the old mc because they use different size lines.

I bought a bench bleeding kit at NAPA when I bench bleed my MC. I was surprised at how long it took to get reid of all of the air. You could also get fittings to make your current lines wotk with the proportioning valvue you have.

Good luck.

[youngrodder]

Originally Posted by mobileortho

I believe it's the mc. I'd used a vaccuum pump to bleed the lines. Had my son the pump the pedal last night while I checked the bleeder and got nothing. I had changed master cylinders right before I started the rear end swap. It's the same type I had before (corvette style) that I swapped ou because I came across this one that had a proportioning valve already attached. It's a new unit that I got from someone who had purchased, then went another route. Can't swap the proportioning valve to the old mc because they use different size lines.

I bought a bench bleeding kit at NAPA when I bench bleed my MC. I was surprised at how long it took to get reid of all of the air. You could also get fittings to make your current lines wotk with the proportioning valvue you have.

Good luck.

[mobileortho]

Found the problem! I disconnected the MC from the booster and compared it to the other one I'd removed. The pin on the booster was too small and not making contact with the plunger when the pedal was depressed. I changed the screw and added a washer that was large enough to make contact to the plunger and the problem was solved.