Still tinkering around with the rear end/disc brake swap for my truck. I added 98-02 LS1 rear discs to a mid 70's Camaro 10 bolt. Finished up the emergency brakes recently and bled the lines but I have no pedal pressure. I bled them twice now with no success. Any ideas on the cause?
Need more details are you running an MC with a booster? Under the floor or firewall mount? Late model MC, separate chambers? Did the truck stop fine prior to your brake work? My guess is: - You still have air in the lines somewhere - You have a leak - Your MC pushrod isn't engaging properly Start with the basic stuff and work your way through the problem.
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 (firewall mounted corvette style with a 7"booster) 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 would check the push rod coming out of the booster to see if it is long enough and engaging the MC properly. If your pumping the pedal like a mad man and it falls to the floor with no fluid coming out the lines... that would be my first guess. The MC could be the same style but could have a different engagement point.
Did you bench bleed the master cylinder? Is it putting out fluid out of the rear port? Sounds like it might have sat on somebodies shelf for a bit, and the rubber in the rear ports might be done. Just a thought...
The brakes need to be adjusted. Rear GM discs are not like fronts. get ahold of Raven61 he's got the later discs on his AD truck and has been through the whole adjustment thing. He can point you in the right direction.
Does the proportioning valve have a little pin on it that slides when there isn't equal pressure. For my truck the pin was pushed way over and I was getting barely any fluid to the rear lines. I put a clamp to hold the pin down and then bled the rear and now I have much better pedal pressure. Your proportioning block might be different though, mine was in an 86 chevy truck.
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 screwand added a washer that was large enough to make contact to the plunger and the problem was solved.
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