'70 Challenger (power front disk/rear drum) brake saga continues

[spamtank]

A while ago, I had a problem with the rear brakes over heating.  So, I've replaced the following:

Emergency Brake Cable (PN RSBCE04 purchased from http://www.adealsauto.com/), and the proportioning valve/metering valve blocks (PNs BLK251 and BLK252 purchased from Inline Tube http://www.inlinetube.com/Prop%20Valves/BLK251.htm).

I bled the brakes with the help of the wife.  She complained that the rear was hard to press to the floor.  I cracked the fitting at the axle Tee (more questions on that part later) and had flow.  Fronts bled okay. 

Took it for a ride around the block.  Seemed to have good brake peddle for a short while, but I noticed that it got soft toward the end.

So this weekend, I decided to bleed the master cylinder separate, with tubes looped back into the reservoir.  Didn't seem like any air was purged.  But I did notice that the larger rear reservoir was cloudy.  I removed most of that cloudy fluid and filled with fresh before bleeding the 4 corners.  I started at the most distant, working my way finally to the closest.  I did this one by myself with the "one-man brake bleeder setup".  And I now understand what my wife was describing.  When bleeding both rear brakes, first inch or two of travel went pretty easy, then it stiffened up, and continuing pressure eventually forced the peddle  to the floor.  The fronts were easy.  I bled both front and back until fluid was running clear.

After all that, I took it for another ride, but the brakes are still no good.  I'd expect to be able to lock them up, but they don't even make an attempt.

I read about at least one other member who had problems with the Inline Tube valves.  I started to wonder if I should have purchased them from Classics Industries.  However, close scrutiny of the catalog photos makes me think they come from the same supplier, even though the part numbers are different from the two retailers.  I don't seem to be having any leaks from the valves, or any where (externally) in the system for that matter.

I'm going to pull the master cylinder away from the vacuum booster to see if there is any evidence of fluid there. 

I know that the collapsed brake hose was suggested as a potential problem.  I'm going to replace the one to the rear axle Tee.  But that brings me to my next question.  That Tee seems to have some sort of vent on the top of it, sort of like the air scavenger on a forced hot water heating system.  It has a thimble shaped cover that has crimps preventing it from lifting off, but otherwise it's free to move.   Is that vent really a differential pressure relief cleverly disguised as a brake line Tee mounting bolt?  Does the rear axle Tee contains sort of pressure proportioning with in it?  I figure if I'm replacing the rear hose, maybe I should consider replacing the Tee as well.

Any other suggestions or comments?

Thanks

Rick

[Bullitt-]

The thimble on the tee is a vent but it's not for the brakes it's for the rear end. 

[spamtank]

The thimble on the tee is a vent but it's not for the brakes it's for the rear end.

Thanks.    That's kinds what I figured.  Are those parts available if I round if off or otherwise damage it?     I don't recall seeing that listed anywhere, but then again, up to now, I wasn't looking.

[Bullitt-]

I've seen them a few places...here's one http://www.rtspecialties.net/proddetail.asp?prod=4032798

[spamtank]

Finally solved my brake problem.  I tried re-bleeding the brakes, to no avail.  Recall that I was not getting good flow to the rear brakes.  So I removed the rear brake line at the proportioning valve.  Still had stiff pedal.

I figured that it must be the new Inline Tube Reproduction Proportioning valve.  I decided to try to resurrect the original valve.  I disassembled it and cleaned 41 years of crud out if it, and inspected all the o-rings, bores, and fluid channels.  The seals were in remarkably good condition for being that old.  I gave everything a good coating of brake fluid as I assembled it. 

I kept the Inline Tube reproduction metering/hold off valve used in the front disk brake circuit, because my original was seized up.  Then I put the freshened up proportioning valve back in.  When I started bleeding the rear brakes, it was immediately obvious the problem was solved.  Brakes are back to what the should be, and not overheating.  I can now drive the car like she deserves to be driven.   

I followed up with a call to Inline Tube Technical Support.  I explained my findings.   Chuck said that the valve needs centering, because sometimes it shifts in shipping.  He said that you need to open both bleeders on the wheels that are getting good flow, and that would center the valve.  I suggested that they should provide this guidance with the valves.  He told me it would be too much trouble to print out these instructions for each one they sell.  They would rather have folks call the Technical Support line after they have had trouble, and then they would give the verbal instructions or email them.   

Interestingly, the Inline Tube proportioning valve doesn't include a centering spring on both sides of the proportioning valve.  In fact, I didn't know that spring was in my original, until I was cleaning the bore out with a q-tip and it felt kind of spongy, and out popped the smallest spring of the group when I turned it on its end.  Probably saved them a buck or two to eliminate it.

I was hoping they would take it back.  Chuck told me that since I already had it installed, they would not take it back.  I'll chalk that one up as a lesson learned and put it on the shelf after I print the instructions out for future reference.  I was going to eventually purchase brake lines, but I won't likely go back to Inline Tube for those.

Hopefully, this will help someone else who has the same problem.