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Discussion Starter #1
Fellows I need a little help I'm trying to bleed the brakes on my Z and can't
get any real presure on the back to even move the shoes.When I hold the
peddle down and open the rear bleed valve peddle stays the stay dosen't go
to the floor every thing has been rebuild except for the brass block on the
sub frame anyone have any idea's Thanks
 

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I had a problem getting pressure to the rear brakes on a 69 and finally tried rebleeding the master cylinder and that was my problem. The master cylinder had air. It is really important to bench bleed the master cylinder. I hope this help.
 

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You probably have the little sub-frame mounted hold-off valve just below the driver's seat. After 30+ they can go bad and cause problems,..rust from the steel lines, old Dot-3 that's turned to yak, etc. and you could have blockage. Try bleeding everything first, check for leaks, then add this valve to list of possible culprets.
 

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You might check the "button" on the front of the master cylinder. If you push it in it will "reset" the little piston in the MC that splits the fluid flow back to center . With a dual braking system it's designed to seal off the side that has lost pressure. If you remove the brake warning switch from the MC and look inside you can see it move.
At least that was the fix when we had the same issue.

joe
 

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Well, here's the wrong way to do it... I had a clog somewhere for the rears of my '68 (base 327 V8 convt, no prop valve). I couldn't get any fluid out of the bleeders in the rear, and had a solid pedal with both rear bleeders open. I started the engine (to let the booster help) and pushed the brake pedal almost as hard as I could, and something finally gave and the brake pedal went almost to the floor. I shut the engine off, and pumped the brake pedal a few times, and it was still going almost to the floor. Then I checked the bleeder screws and fluid was flowing out of them.

The right way would be to crack open lines until you can isolate the blockage. My first guess would be the prop valve on the subframe since it sounds like you have one.

Side note--I did mine the wrong way because I had already planned to take the car off the road soon and just wanted to get it driveable for the nice weather that weekend. I've since replaced the entire rear braking system from the splitter back. New stainless line, new flex hose, new tee, new lines on the rear end, and shiny new Wilwood calipers.
 

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Discussion Starter #6
Thanks I'll try all of this tonite buy the way I'm using silicone fluid if it makes
a difference
 

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I haven't been keeping up. I know Dot-3 and Dot-4 are ok with our old brake systems but is silicone? Seems I recall a discussion about incompatibilty with the seals used in old rigs. Might do a search.
 

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I recently had the same problem with a '71 GTO which had sat for 6 years. Ended up changing all the rubber brake hoses. No fluid to the rear brakes or the right front, but crack the hose inlet fittings, and you'd get fluid. They swell up inside, and/or delaminate, allowing a flap of the hose lining to fold over, act like a check valve.
 
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