Ok, a little story here. I'm 33, been doing this a while. Probably rep'l 15 master cyl's in my life, done conversions, etc. This ain't my first rodeo. I CANNOT get the rear brakes to work on my 72 Monte. I'm on my third master. I've replaced the wheel cylinders. I've replaced the rear hose. I Put on a junkyard prop valve out of a 74 Chevelle. I've shot air through the rear system and all is free and clear. All i get is air and a dribble of fluid for the first few releases, then bupkis. Even with the new prop. This all started with a slow seeping leak @ the mate between master and booster.Fronts have seemed to work fine through all of this. So here's a few questions.

1. How does one check for a bad prop valve?

2. Is it possible that I have screwed up the bench bleed? Never have before, but always a first. As stated in the directions, I put in the plastic SOLID plugs and pumped the plunger until I got no air upon kickback. Never saw this method before, always had plugs w/hoses in them run back to the reservoirs.

3. Is it possible that a misalignment between the booster is knocking out the rear ports? On the 2nd master, had no fluid @ the rear port, loosened the mount bolts, neighbor kicked pedal by accident, and she shot fluid everywhere.

4. Any truth to the rumor about the short booster thing? I have about half my pedal travel gone before I feel ANYTHING on the current master, much less resistance.

5. I can buy a matched master/booster set for $90 from Oreilly. This worked well on my brother's conversion in his 67 Velle. Ya think?

Any help is appreciated, as I am truly at my wits end with this nicely painted, leaking, pig-rich, no brake piece of #@@% ! TIA, Chip.

If you crack the line going to the rear brake port of the prop valve. Do you get air/fluid or not?

If no fluid, the your master's front plunger is sticking internally or bad.

This can happen on a new master too, where it has been bled (pushing plunger in) too agressively before it filled with fluid. Never more than 3/4 push. Of course, if you saw fluid going from the ports when you bench bled it, then it's ok.

Afer that then it's the pedal rod to master relationship, as I have never had a bad prop valve. Leak, but never go bad.

I will crack the lines open after the master but before the prop valve to rule out the master/pushrod issue before changing the prop valve.

Check out MPBrakes (http://www.mpbrakes.com) for more troubleshooting info.

Try gravity bleeding for an hour or so. Many times it is damn near impossible to get the sytem to start bleeding properly until you get most of the air out already. Could also try reverse bleeding, that requires a 200 purchase of the bleeder though.

sounds like the pushrod might be a little to long
try backing the nuts off of the master cylinder itself about two full turns and try bleeding them again
if they bleed now the the pushrod is too long or the pedal to power booster is to long
also try bleedind it with the car running and push the pedal slowly and release it slowly to pump them up about 3 or 4 times before opening the bleeders

DG- I went there on the last prop valve NADA- Too po'd to look this time. I'm with you-never seen a bad prop. Tried cracking the lines on #2 master- haven't on this one as I think it's a short master and might be goin' back to the parts house. Went easy on the bench bleed on this one on purpose. Saw turbulence @ the ports on both wells.

Dennis-Tried gravity. As usual, got 2 good squirts then zilch. Seems like it seeps down w/ gravity, but not under pressure. I know what you mean w/the reverse thing, but I've never needed it in 15 years. somethin' ain't right.

Tom- That's what happened w/#2. Then, nuthin again. Tried it w/the car runnin' and same result.

Thanks for the replies! Any one else feel free even if it sounds dumb! This is why I'm asking, cause I've tried every trick I know and even visited some good shops, and I've got squat. Thanks again, Chip

You could use this tool to reverse bleed.
http://www.mpbrakes.com/ac20010.htm

Update: I went ahead and ordered the booster/cyl combo (matched set) and I'll have it today. If this ain't it I'll have to douse it in gas ian throw matches at it!

It sounds like what when we swapped from drum to disc in the burb. Would work like 3 times then nothing, no pressure @ the pedal NOTHINg. Ended up being the pushrod was to long, we cut about 1/4" off the rod and there we go. To test this we also just backed the nuts off the master and tried pushing on it.