Rear brakes don't have enough oomph

[ronfis]

I completely refurbished the brake system in my '57 Oval. The front brakes work fine, but the rear wheel cylinders only work when the brake-pad springs are disconnected. The system has been bled fully. Any thoughts?

[splitjunkie]

Did they work before you did your work?

Did you replace all of the hard lines and the rubber lines?
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Chris

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[ronfis]

Splitjunkie: The car was in lousy shape when I got it -- the old wheel cylinders were rusted in place. I replaced everything. When I pull the springs off the brake pads and press the brakes, the cylinders move so far that the rubber seals separate from the cylinder housing. With the springs on, no movement. Thanks.

[57BLITZ]

An early master cylinder is a single circuit that provides equal pressure to all four corners.
A plugged line (or possibly the tee fitting) would cause a problem, but then you would not be able to bleed the rear wheel cylinders properly.
Are all the brakes stock (type) drum brakes?
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[slalombuggy]

A sealed hydraulic system will have equal pressure in all directions no matter how many points there are in it. Did you kink the front to back line or has it been pinched somewhere. A restriction in the rear lines is the only reason you will not have the same pressure front and rear. Since it affects both rear cylinders the same I would examine the front to back line.

brad

[ZENVWDRIVER]

... what did you replace? You might have to replace hard lines and flex lines to the back... sounds like a blockage, to me.
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[tisius]

You stated that you've replaced everything; could you have made a bent in one of the hard brake lines (most likely the longest line which runs along the tunnel from front to back) too sharp, which would now obstruct the full flow of brake oil to the wheel brake cylinders in the rear?
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[Snort]

You either have failed seals inside the master cylinder, or you are mistaken when stating that the system is fully bled, or both.

I ran into a problem doing some brake bleeding last year on my Vanagon and the solution for me was to push a little bit of brake fluid from the wheel cylinder back towards the master cylinder and that was all it took to dislodge a pocket of air inside my master cylinder. You can even use air to push a small amount of fluid back up the line, then bleed that air out again.

[ronfis]

Guys: Thanks to all. Grteat ideas, and I appreciate the help.