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Thread: Bleeding Brakes 79 CS

  1. #1
    Member ianmcc's Avatar
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    Default Bleeding Brakes 79 CS

    So I am having quite the time trying to bleed the brakes and I am posting up to see what I am failing at.
    Background-car is a 1979 Country Squire so no ABS. Replaced all of the rear brake lines right to the wheel cylinders. Replaced the soft line as well.
    The original distribution block/proportioning valve or whatever we call it was full of dirt and seized up so I replaced it with one from the 85 CV in the local picky pull.
    Underneath all the dirt and road grime it was full of actual brake fluid and cleaned up fine.
    Also replaced the hard lines from the master cylinder as the originals were rounded off and had seized fittings.

    So the problem is I can't get any brake fluid to the rear brakes. I have tried pumping them up and holding them but the rear brakes spin freely but the fronts lock up and only release when I crack the bleeder screws (one good thing-none are seized). I use a vacuum pump to bleed them but nothing except residual drops.
    Tried gravity bleeding and nothing flows. And I did remove the stop switch and put in a stopper to keep the shuttle valve in place.
    From what I understand is the valve assembly does two jobs-proportioning brake fluid to front and rear and a pressure regulator.
    This is the original stripped down aluminum one from my car. Gives you an idea of the one I replaced it with.

    Click image for larger version. 

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    So there is a button under the rubber cover on the back. My understanding is it is a bleeder rod. Bleeder indicates it may have something to do with bleeding.
    Is it a reset button of some kind? Do I press it in or pull it out when bleeding brakes? I have seen pics of vehicles that have a tool that either pulls or depresses and holds the rod while bleeding. Example...

    Click image for larger version. 

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    I have bleed brakes countless times but this has me stumped. It is like something is keeping the fluid from flowing but except for the brake cylinders everything in the rear has been replaced.

    Advice?

  2. #2
    Fastest Boxes In South Jersey 86VickyLX's Avatar
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    Default

    I am assuming you've replaced the rubber brake hose that's on the center of the rear differential?

  3. #3
    Wagon Addicted Tiggie's Avatar
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    "I have tried pumping them up and holding them but the rear brakes spin freely but the fronts lock up and only release when I crack the bleeder screws"

    So the back is getting nothing and the front is holding pressure (assuming you don't open the bleeders)? I'd be looking really hard at the master cylinder.

  4. #4
    Donating Member massacre's Avatar
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    Fronts are locking up and won't release
    Rears have no fluid.
    When gutting the stock prop valve, it is recommended to install an adjustable prop valve.
    ..

  5. #5
    Donating Member massacre's Avatar
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    Fronts are locking up and won't release
    Rears have no fluid.
    When gutting the stock prop valve, it is recommended to install an adjustable prop valve.
    ..

  6. #6

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    Replace the rubber lines to the front brakes. The rubber is disintegrating, and a small piece is probably obstructing the flow, and acting like a check valve. Enough pressure lets the fluid into the caliper, but it won't flow in the opposite direction when you take your foot off the pedal.

  7. #7
    Member ianmcc's Avatar
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    So to update a bit and add more info; front passenger side has a new caliper and hose I installed previously and the drivers side is rebuilt (couldn't get a new one locally) and the hose was also replaced in the past. Both calipers are a later design with the banjo fitting.
    I decided to basically tear back into the entire rear brake setup and blow brake cleaner through everything to ensure no blockages.
    That includes all of the new rear lines and yes a new rubber rear hose splitter.
    The combination valve (I am going to call it that now) was taken apart and cleaned but it looks like I missed the rear section which looks similar to this.

    Click image for larger version. 

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    The basics are the same-I borrowed this pic from https://www.musclecarresearch.com/articles as I picked up some ideas from the links.
    The GM 10223533 Combination Valve looks very similar to the Ford unit I am working on.

    This part of the combination valve was filthy and the black gasket on the red valve thingy was stuck inside.
    Cleaned it out as best I could and re-assembled.

    Took apart both rear wheel cylinders and it not surprisingly it appears neither one had fluid in them. But both were dirty but not terrible. And the passenger side was fairly seized up. Took some work to get it apart. Ran a small hone lubed with brake fluid through both cylinders and both cleaned up nice. No damage to the rubber nor the pistons and took the time to run a tap through all the bolt and bleeder screws and lots of brake clean before the reassembly and re-install.

    After buttoning everything up I filled the master cylinder with the last of my fresh fluid. Used a vacuum pump and was able to get fluid passing through to the furthest brake.
    Then set up a gravity bleed and walked away while I cleaned up and ran to Princess Auto (Canadian eh?) for more fluid.
    Came back to a considerable amount of fluid in the jar. Success! Moved over to the captains side and repeated the process. Only got a bit more fluid on that side but at least things are flowing.
    Today the plan is vacuum pump all four and see what transpires. Will update as I go.

  8. #8
    Member ianmcc's Avatar
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    Should add that I did have fluid in the lines I disconnected so the issue may have been filthy wheel cylinders since they were dry.

  9. #9
    Donating Member massacre's Avatar
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    Great to hear you get it fixed!
    ..

  10. #10
    Member ianmcc's Avatar
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    Test driving and they are a little soft so some more bleeding is in order.
    But now I found a few rad leaks that turned into a geyser! And a fuel leak from the drivers side frame rail. If it's not one thing.....

  11. #11
    Beater gonna beat sly's Avatar
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    Bah. But progress.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

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