[KyleSeal]

Originally Posted by MikeB

I once had a pressure bleeder kit and never could make it work right. But it was great for making a mess!

How about old fashioned manual bleeding? That's where a helper does "pump, pump, pump, hold" and then you open the bleeder screw. Then you close the screw and repeat the process until there are no more bubbles. If you get very little fluid out the wheel cylinders using that method, then I give up.

I've also used a MityVac, which works fine, but as mentioned a couple times in this thread, it will suck in air past the bleeder screw nipple. Makes it look like there's air in the lines when there's not -- or probably not.

I tried the two person method tonight, and I got little to no pressure, I tried even punching the pedal to rush fluid - nothing. I have found at the tee on the rear end, one side will not drip any fluid or maybe once when I crack the line open, one side will run like a river. I am thinking I have an issue there. Which is so strange - I had no issue before the master cylinder swap.

Originally Posted by dmjlambert

Interesting behavior. Brings me back to wondering if the master cylinder has front reservoir for for rear drum brakes and rear reservoir for front disc brakes the way they are typically set up for C20.

As mentioned in this other recent thread by geezer#99 and earlier in this thread by kwmech the master cylinder may have residual pressure valves that are specific for drum or disc, and the residual pressure for drum is greater.

I don't know the confidence level that should be trusted in what the "people who sell these" saying about the design of it. I would want to see the actual specs and would like to have the tools and equipment to do measurements (like for the residual pressure, as if I would know how to measure that). It's hard to put a brake system together and trust that the specs are right. This thing you're going through is mysterious and I wish I had advice to remove the mystery and just determine the facts.

The action I would take is highly biased so you may not find it useful, biased by my preference for manual brakes on a C10. So I'd be putting a manual master cylinder that I know works for disc/drum on the firewall and call it a day. The manual master cylinder has a deeper bore for the push rod. Kit type master cylinders often have a deep bore and an adapter pin that fit in the push rod hole to make it compatible with a booster that requires a shallow push rod hole. I'm sure there's not very much to adapting a deep push rod hole to a shallow one, it's just a small rod of metal. So perhaps one of those manual master cylinders could be adapted for power, or a different power master cylinder that somebody here on the forum can attest to working on a C10 could be used. 71-72 C10 that came from the factory with disc/drum had 1.125 bore regardless of whether they were power or manual, and that has been shown to us by Keith Seymore right from the engineering specs he posted. A MC with 1 inch bore is not to spec for a C10, I'm not saying it won't work, it just reduces my confidence in the people who sell these kits and makes me wonder what the heck. Anyway I ramble, sorry too much rambling, saying bye now and I hope you find the solution.

Originally Posted by dmjlambert

I agree with regular manual bleeding is best, it's just simple. I tend to use the one-man method that does not require a helper. It is where you put the hose at the bottom of a jar that has some brake fluid in it, and open the bleeder. Then once that little bit of air is pumped out of the hose by brake pedal action, no more air can be sucked back into the system. Pump the brakes gently and slowly until you mostly fill the jar, and replenish the MC periodically. Then close the bleeder before removing the hose. O'Reilly auto parts have one-man bleeder kits, but it is also OK to just use a coffee can and submerse the end of the hose. If you think you're getting any air past the bleeder threads, you can remove the bleeder and put a little chapstick on the threads, and re-insert the bleeder screw.

I am at the point I may end up buying some special brake pressure measuring tools to help determine some of my issues. At this point, I may be disassembling the rear ends brake lines and tee, to check for blockage, if none is present, my next move will be diagnosis with specific tools.
I normally do the one man method, but I cant even get a small amount of fluid from the rear. Its mind boggling. Even punching the pedal does nothing. I figured a pressure rush would at least make it do something, but nothing at all.

Originally Posted by MikeB

About master cylinder built-in valves, I cut this from a post on The H.A.M.B.

An easy way to check any dual master is to take a paper clip or similar small diameter object and slowly push it into the output ports. If you feel a spongy resistance, you are pushing against a residual valve. If none are present, the object will easily go into the master bore.

I seriously doubt if yours has a built-in valve or valves. Everything you need is in the combination valve.

I will check this next as well.

Originally Posted by dmjlambert

That is interesting information. There's too much general information that's confusing, and not enough actual technical specifications about what is in each component. I understand the factory combination valves don't have residual valves, they just have the shuttle switch, metering valve (for 71 manual brakes they didn't have one, but for other applications they did), and proportioning valve. Who knows what is in the chinese brass block style replacement combination valves. I'm kind of doubting there are residual valves in there. The residual valves would have been in the master cylinder way back when, but there is other information on the internet about modern wheel cylinders not needing residual valves any more and who know the specs on the master cylinders they are selling in parts stores (or anywhere).

Originally Posted by geezer#99

Did you measure the bore yourself or just look at a spec sheet?

These measurements are from their spec sheets. I am not versed really in most brake system specifications, more so a general sense, which seems just enough to get me into trouble at this point