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Thread: Spongey brakes

  1. #41
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    Quote Originally Posted by westy1 View Post


    For me that's clearly showing the lower, rearward piston (secondary system) in a metric system (81 ish onwards) gets its supply from the bottom calliper port.

    Which piston is which is clearly shown in a METRIC era layout diagram.

    And this is showing the primary bleed screw is connected to the upper port.

    Thanks Westy.

    DL

  2. #42
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    Quote Originally Posted by DoubleChevron View Post
    How does the twin circuit brakes work inside the master cylinder? Possibly the primary circuit circuit is leaky internally inside the master, so you're ending up one the secondary circuit, even though they are both bled ?

    Attachment 177366


    Here we go. Do the back brake work? if they are't working, I'm betting the primary circuit in the master is dead.

    Actually, what you are saying is 100% right. The differential/priority switch may be stuck over on the secondary circuit. Same deal, do you have rear brakes ?
    That diagram is how the imperial system worked. There was a shuttle switch in the proportioning valve that operated the brake warning dash light if either circuit faiied.

    On mine (AP M/C metric...... 81 body and brakes) only the secondary system runs through the proportioning valve, the warning light switch is on the side of the M/C, as per the WSM.

    The later ones (Lucas Girling M/C) use a float switch on the M/C tank for the brake warning light.

    DL

  3. #43
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    What's the difference in the WSM layouts pre front flexi pipes shown here?

    The first is AP M/C, the second is Lucas Girling.

    Remember the top flexi tubes go to the lower (secondary) calliper ports.
    Attached Images Attached Images

  4. #44
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    The WSM diagram below is for the system with the Lucas Girling M/C.

    Assuming the layout is the same each side at the front from the flexi hoses onwards (top hose goes to bottom port on the calliper ......... secondary system) who can spot what's wrong?


    LucasGirling metric brake layot.jpg

  5. #45
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    Even tho it’s from an 81,These are imperial AP Lockheed calipers.
    As per the videos,following the hardline pipes from the bracket where they join to the Flexipipes,the top line feeds the upper bleed nipple,the lower pipe shares feed to the two mid caliper bleed nipples.


  6. #46
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    Quote Originally Posted by westy1 View Post
    Even tho it’s from an 81,These are imperial AP Lockheed calipers.
    As per the videos,following the hardline pipes from the bracket where they join to the Flexipipes,the top line feeds the upper bleed nipple,the lower pipe shares feed to the two mid caliper bleed nipples.

    All the AP callipers I've seen (imperial or metric) have the same internal plumbing as you've pointed out.

    All have had the top hard line from the flexi hose junction going to the bottom (secondary) port on the calliper and the bottom hardline going to the upper (primary) port on the calliper.

    As per your original pic:

    9ACFE250-3F58-4536-B339-D3B1D2E55D29.jpg

    and the WSM:

    Calliper lines.jpg

    It's easy to get the pipes bent when the calliper is off the car and being played with.

    Another issue is what was doing my head in years ago................

    The WSM shows the hard lines going from the primary M/C ports (closest to the booster) to the rear of the brackets each side above the flexi lines.

    AP metric brake layout.jpg

    Mine went to the front of each bracket FROM THE FACTORY and still do................ took me ages to figure it out, after I'd installed new flexi's according to the diagrams of flexi lines in all the books.

    Of course it wouldn't bleed properly till I simply swapped the lower ends of the flexi lines to the other circuit at the hard line unions on the hub.

    Bled straight up and has been fine ever since. Was like a revelation.

    I'm not saying everyone may encounter the same issue ............the thing to check is each line, on each side, needs to be traced from the primary and secondary ports on the M/C to the primary and secondary ports on each front calliper if there is an issue bleeding the ****ing thing.

    cheers, DL

  7. #47
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    Quote Originally Posted by 350RRC View Post
    What's the difference in the WSM layouts pre front flexi pipes shown here?

    The first is AP M/C, the second is Lucas Girling.

    Remember the top hard line tubes after the flexi lines go to the lower (secondary) calliper ports.
    Just fixing a typo in a previous post.

    DL

  8. #48
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    At the end of the day, if all the pipes are going to where they're supposed to, the only reason for the system failing to bleed properly is because people are using the one man bottle bleed method or a vacuum bleeder, instead of the two man method of opening and closing the bleed nipples with each slow pump and release of the pedal.

    The nipples threads do not seal well enough in the callipers to anything but the latter IME.

    cheers, DL

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