Haha! Adjustable?

My 70 may be going to rear discs in the future so it'll already be set up for such an upgrade.

 

I still don't think you're wrong.
Notice how the disc side is spinning free while the drum side pumps up?
My WAG is the pistons are backwards.
I could be full of prunes but as long as we are theorizing.

 

You make me laugh.

 

Yeah Marc, I'm having second thoughts about my second thoughts (I really should stop over analyzing ).
I started thinking that because the drum brakes actually have fluid flow as the shoes expand and contract that the fluid should go up and down, but the circuit is already filled with fluid to move the shoes. The reservoir is there just for a reserve and the level shouldn't change........I think .

Anyone ready for over analyzing round three .

 

This is the fun stuff.

 

Yeah after watching it again(and again) I can see what you are talking about. There is plenty of pump to clear the lines and you can see the bubbles in the reservoir.

 

I tink I'm gonna tear my $29 rebuilt OEM MC apart to see what the innerds look like. Great thread for a noob like me.

 

I'm actually thinking of forgoing the return reimbursement and taking mine apart also just so I know what is going on.
Have to say I'm done with cheap replacements from the auto parts store.
This has been a weeks worth of r&r (not the good kind).

 

Well, I tore apart my old MC and it was a little more complicated than I thought. Each cup seal goes past two orifices, the first is 1/8", the smaller one measures about .020". I guess the second small orifice allows the pressure in front of both cups to equalize before going past them?

You can see the front orifice, the back one was full of crud, but it's there.

I'm glad I replaced it, 'cus it was full of crap.....and now I am glad I ripped out ALL of the old brake lines.
I hope this helps Turbo.
Let the analyzing begin.

BTW - my wife saw your sig pic and thought it was hilarious.

 

Cool
Glad you posted that pic.
That'll give me a good comparison.
I'll get to mine tomorrow, gotta work today.
BTW got my new mc from CCP. It's freakin beautiful.
It's gonna look awful lonely in that engine bay being all chromie with all that nastiness around it. But soon to be joined by a brand new engine and more chrome.
I like chrome.

On the sig pic, some kid called me an *** a while back on a thread so I thought I'd own it.

 

Ok fellow theorists settle in this may take a while.
I'll start by going over the new mc.
It's a thing of beauty. It's made of aluminum with a chrome finish. Not polished.






The bowls are huge compared to an OEM. And there is a leveling passage between the bowls so that it can use fluid from the other bowl so it's pretty hard to run it out of fluid. You still have separate circuits for safety but there is an additional level when you have a bigger fluid supply.





The integrated proportioning valve is what really turned me on. The plumbing is now so simple it's great. I'm trying to keep as much room as possible in there to fit all the new engine stuff. So for me it's a win/win.



Bleeding and installation was normal. They even give you a little syringe with a curved tip to suck out air or force in fluid to the bore feeds.



So Sunday I installed the new mc and while I was at it changed out the rear wheel cylinders so that in my head I have a brand new system to start with.
All went normal, but I could still only get the rear brakes to work. WTH.
That was the end of Sunday so I came to work yesterday and had lots of sitting around time to think about it.
It didn't help this whole process that I got a bad mc, but, that is what got my attention and is where my theory starts.
We know that it worked before, we know that I had a bad mc the second time.
That got me thinking, the first mc worked then nothing after I replaced a line.
Why?
Here's what I think happened.
The bores/fluid chambers of the calipers are round. The bleed screw is at the highest point of that chamber so that air can escape through the highest point and not be captured inside.
When I put together my front end I put on 7 degree bushings which rotates the housing backwards which rotates the bleed screw basically counter clockwise leaving it below the actual top of the caliper bore. This is usually offset by the lift on the truck rotating the housing back towards the front end.
When I first did the bleed job the front housing was at full droop on jack stands so the bleed screw had the proper relationship to the bore.
Then I set the truck down and drove it and everything was fine because it had been bled with everything in proper relationship.
Now, I take off a line to make it better and re bleed the system.
Everything should work right?
Wrong, the truck is now sitting on the old springs that have not been replaced yet, so the axle housing is rotated towards the rear lowering the bleed screw below the to of the caliper bore thereby leaving an air pocket in the top of each front caliper.
Still bleeds fine but there is an air pocket that can't be bled out.
So, how do I fix it.
Friday I have the day off. I'm going to install the new springs and let the axle housing fall to full droop then re bleed. If that doesn't do it then I'll take each caliper off and stick a spare rotor in there and bleed again with them in optimum position.
If that doesn't work then I already have them torn apart for r&r.
If this works then I have you all to thank for keeping my head in the game.
I'll let you know how it goes.

 

That kinda makes sense Marc, you've covered everything else it could be. This type of theorizing is called "process of elimination" .
You beat me to the punch with your solution. I was going to say remove the calipers, block the pads, point the bleeder screws in the right direction and have at it.
I hope this solves your problem, if it doesn't I'll probably hear the screams all the way in Florida.
Good luck
PS: That is one nice lookin' MC.

When ya gonna add hydroboost?

 

You're the devil.

 

Looks like you have it handled.

I can play demon to the devil! I LOVE MY HYDROBOOST!!!!

 

With friends like you guys......................