Master cylinder help

[erock805]

When I got my 64 it had a cpp master cylinder (power) unit. It has the cpp distribution block an al.. the Power unit looks like a stock unit.

Went to bleed the brakes today. Got the fronts to push fluid all the way to the disc brake calipers. I cant get the rears to get any fluid. So I started at the master cylinder and found that no fluid would come from the rear outlet on the master cylinder itself.

So...the fronts work. But the rears push nothing. Any ideas?

[jocko]

Assuming the master cylinder fluid passage to the rear port isn't physically blocked (i suppose it could be) then the only other "easy" thing I can think of is the proportioning valve (you mentioned cpp, so am guessing a prop valve came with it also? - if not, then disregard this jibberish) - maybe it is adjusted/biased all the way to front wheels only. If not that, the only other thing I can think of is a possible mismatch in brake pushrod length (since it sounds like there has been some mods done to the braking system) with the result of not pushing the master cylinder piston in far enough to uncover the rear brake port. But I'm guessing a little bit on that last one...

[markeb01]

Another possibility is the master cylinder wasn't bench bled before it went on the truck. If it sits on the truck at an angle, air will be trapped inside and you'll never get it out.

Here's a link showing how:
http://www.superchevy.com/technical/...nch/index.html

[erock805]

It doesnt push fluid right out of the master cylinder... so its not the distribution/proportioning valve.

I will try to bench bleed it next weekend...