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Thread: Another brake bleed problem!

  1. #1
    Jim Arnett jfa.series1's Avatar
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    Default Another brake bleed problem!

    Iíve spent this week installing new springs and all is complete, now its time to bleed the brakes. I cannot get a flow of fluid to the rear brakes.

    Iíve bled the MC twice Ė once with a vacuum bleeder, once with the old pump-bleed-tighten-release method. Iíve repeatedly tried to bleed both sides of the rears but cannot pull fluid with the vacuum bleeder. I even disconnected the RR hard line on the body that connects to the flex line and attached the bleeder. It pulled a solid vacuum and held it for 30 min. with no flow. Here are a few other bits of info:
    - Everything was working properly before I started the project.
    - The MC is ĒnewĒ, only two years old and about 2k miles since the resto was completed.
    - The front brakes bleed just fine.
    - The pedal is very hard with only a little movement Ė even if the rear bleeders are open.
    - I drove the car a few feet to check that the MC is working Ė itís clear only the front brakes were actually being used.

    I really need some ideas on what is blocking the flow to the rear. Iíve checked the archives but just did not spot any old posts with the same symptoms. This is a real hair-puller - except I've none to pull!!!

    Thanks in advance for suggestions.

    Jim Arnett
    HLS30-15320 12/1970, original owner
    L24-020208 (original)
    IZCC Original Owner Registry #53

  2. #2
    Barn Find Daily Driver Captain_Zeros's Avatar
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    Default

    Brake proportioning valve?
    1973 240Z w/ roundtop carbs, 280zx e12-80 distributor, 280zx alternator, late model Altima junkyard electric fans. 115 Blue Metallic & white side stripes.

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    Default

    That sounds like what happened to me after i rebuilt the rear wheel cylinders. So I had a dry rear system. I started on the LR. I barely got anything to flow. It would seem the master would slowly refill back up when I let off the pedal. After about an hour I decided to try the LR and it bled normally. Then went back to RR and it bled normally.

    This is what I used. Longer clear hose than what is shown and placed on a bench beside the wheel I was working on. I could watch it while in the car when pumping the brakes.


    I do have one of the air assist brake bleeders, but only bought it to get the self filling reservoir.
    things will only bother you if you let them.

    82 280zxt 4 spd auto
    73 240z--lsd, cv axles
    short throw info

  4. #4
    Jim Arnett jfa.series1's Avatar
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    Quote Originally Posted by Captain_Zeros View Post
    Brake proportioning valve?
    I think we have a winnah!!!

    Working upstream is a great idea - lots of fluid available on the master side of the valve, dry on the other side. Now to figure out if I can clean/service this thing or have to replace it. The FSM has great diagrams and explanation of operation. Its off to the archives again.

    Thanks for the input!

    Jim Arnett
    HLS30-15320 12/1970, original owner
    L24-020208 (original)
    IZCC Original Owner Registry #53

  5. #5
    Registered User LeonV's Avatar
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    Quote Originally Posted by jfa.series1 View Post
    I think we have a winnah!!!

    Working upstream is a great idea - lots of fluid available on the master side of the valve, dry on the other side. Now to figure out if I can clean/service this thing or have to replace it. The FSM has great diagrams and explanation of operation. Its off to the archives again.

    Thanks for the input!
    Same thing happened when I was helping a buddy bleed his Z. He ended up getting a regular tee to replace the prop valve and installing a Wilwood adjustable in the engine bay.
    2/74 260Z

  6. #6
    Jim Arnett jfa.series1's Avatar
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    Leon - thanks for the suggested alternative.

    Of course, this valve is NLA from Nissan and it turns out the FSM is really a tech writer's physics exercise with no details on servicing said valve! So... has anyone ever successfully disassembled and reassembled one of these critters? I tried tugging on the end of the plunger to see if it would easily full free but no joy. Please keep in mind this is the rear valve - none on the firewall for my car.

    Jim Arnett
    HLS30-15320 12/1970, original owner
    L24-020208 (original)
    IZCC Original Owner Registry #53

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