Brake problem?

1990 Dodge RAM, 4x4

Well I'm still going freakin nuts, here's the full run down of where I'm at and how I got there:

I'm driving along going down a hill, go to brake and I suddenly I have no pedal, the 4 wheel light thing on the dash flashes for a second. I pump the pedal and it comes back up and I brake fine. As long as I pump it a few times the pedal comes back.

I drop it off at my son's as he's a mechanic so I get him to do most of my work, he owes me :-D Anyway, he has a look under the hood because I mentioned I had some leaks as well so could he check it out, the power sterring pump is about empty so he figures there's a vacuum issue. Topped up the pump, no difference. Pulls the back brakes off, they're cracked and totally worn out, replaced them, front looked ok for now, bled the system, still no pedal. The RWAL system has been bi-passed at some time so it's not a factor. Replaced the master cylinder, bench bled it, no pedal. Got another master as the first one was a rebuilt and maybe it was crap, this one was new, bench bled it to death and bled the whole system again, no pedal, pressure bled the sytem, no pedal. :angry7: Oh, and there are no leaks anywhere, wheel cylinders work fine, calipers seem fine although he said one was a little wonky so he gets another.

At this point he takes it to the brake shop a few doors down from his shop. They conclude that the calipers aren't working quite right and the rotors are screwed up, they replace them and guess what, no freakin pedal :angryfir::angryfir::angryfir: There's 4 brake techs staring at this thing without a clue. If you clamp the line by the caliper you have full pedal, unclamp and it's gone :banghead:

What the hell could be wrong???? :cussing:


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