Dual Master Cylinder Bleeding

[dstrausb1]

Hi Board.
I’m trying to do the dual master cylinder conversion per the Uglytruckling.com article and I’m having a problem bleeding the brakes.
I’m using master cylinder “Cardone 10-1584” which my auto parts store says is equivalent to the cylinders mentioned in the article. I’ve followed the bench bleeding instructions. I’ve plumbed the front axle to the chamber nearest the front of the truck, the larger chamber, and the rear axle to the rear most chamber, the smaller one.
If I open both a front and a rear bleeder and pump the peddle, the peddle goes down fairly easily and I get fluid out the back bleeder, but none, or at most a couple of drips, out the front.
If I close the back bleeder and pump the peddle, the peddle goes down a couple of inches and then gets firm. Continued pressure on the peddle has it slowly going down, maybe another six inches over 30 seconds. I get a couple of drips of fluid out the front bleeder sometimes and sometimes not.
If I take the front line off at the master cylinder, fluid leaks out from the cylinder without pumping the peddle and a few (dozen maybe) drops of fluid also come out of the bleeder, by gravity I guess.
I originally believed that the master cylinder was defective but I’ve put on another with the same results.
What little I know of brake systems causes me to conclude I’m probably doing something wrong.
First thought is that a dual circuit system might have to have both circuits bled simultaneously because if one circuit is empty of air and that bleeder is closed, then the peddle will go hard. Is this right?
If so, do I just keep pumping fluid out the rear hoping to eventually get enough out the front to do the job?
Second thought is, I wonder if I should have plumbed the axles to the opposite chambers (though I don’t see how that would affect bleeding)?
If anyone has got any suggestions I’d sure appreciate hearing them. I’ve been fiddling with this thing since March and I want to get her back on the road.
Thanks,
Dan

[MSeriesRebuild]

The best way to do it is with the use of a pressure bleeder. You can easily destroy a new master cylinder by pedal pumping, especially if you are pushing it all the way to the floor. Also Cardone is a rebuilt M/C, you are better off to source a new M/C.

Other issues could also come into play. Do you know that the lines, hoses, wheel cylinders, etc in the front circuit are in good shape? If you are not sure, you'll need to check all this in search of other issues. I'm not sure of what you are doing other than adding a dual circuit M/C. If you are doing this on an otherwise unchecked system, that is not a good idea. It is best to change the M/C over during a complete system rebuild.