Brake bias/proportioning valve clean/rebuild | FerrariChat
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Brake bias/proportioning valve clean/rebuild

Discussion in '308/328' started by Dockboy, Jan 9, 2023.

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  1. Dockboy

    Dockboy Formula Junior
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    #1 Dockboy, Jan 9, 2023
    Can the brake proportioning valve be cleaned or rebuilt?

    My rear brakes are working harder than the fronts and when the connector is plugged into the valve, the "brake failure" light is on.

    Thanks
     
  2. ragtop1

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    #2 ragtop1, Jan 9, 2023
    Last edited: Jan 9, 2023
  3. Dockboy

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    #3 Dockboy, Jan 9, 2023
  4. ragtop1

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    #4 ragtop1, Jan 9, 2023
    no problem, I had a similar issue with the warning light coming on and rebuilt the valve
     
  5. Dockboy

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    #5 Dockboy, Jan 10, 2023
    ragtop1,

    How did you get the pistons out?

    Thanks
     
  6. ragtop1

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    #6 ragtop1, Jan 11, 2023
    I only had to replace the electrical switch part # 108955 and then crimped on a new spade connector from the original wire feed. I think it was about $30 for the part. It was a few years ago and it corrected the warning light issue.
    I didn't remove the pistons, so I'll admit it wasn't a complete rebuild.
    From the links above, some remarks state that they didn't have a problem removing the pistons, while others took the valve to a brake shop and needed a press to remove them.
    I was fortunate that my problem went away by just replacing the switch and the pistons weren't seized.

    If your Ferrari valve is seized beyond repair, perhaps purchase the replacement Volvo valve part # 1273052 (less than $100)
    The OEM Ferrari is about $1400 - ouch!
    Sorry I couldn't have been more help with the piston removal.
     
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  7. Dockboy

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    #7 Dockboy, Jan 11, 2023
    Thanks.

    I pulled it out last night. Removed the cap and switch. the switch area was completely gunked up and the pistons are pushed towards the closed end of the body. I have it soaking in penetrating oil, but am not holding much faith that the pistons will free up. I'm going to try blowing the one out with air later.

    As soon as I had it apart and saw it, I ordered the Volvo unit! LOL!

    By the way, I believe the connector has been disconnected for years! When I rehabbed the suspension and steering rack, I noticed it disconnected. Connected it and the light came on.

    Thanks again for your help!
     
  8. ragtop1

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    #8 ragtop1, Jan 11, 2023
    The previous owner disconnected it to turn off the warning light. He wasn't as ambitious as you are to fix it properly.
     
  9. absostone

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    #9 absostone, Jan 11, 2023
    Anyone know where to get those seals on the pistons?
     
  10. ragtop1

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    #10 ragtop1, Jan 11, 2023
  11. Dockboy

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    #11 Dockboy, Jan 12, 2023
    absostone and I have this valve

    [​IMG]
     
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  12. Dockboy

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    #12 Dockboy, Jan 12, 2023
    I'll take a picture of the seal and numbers I was able to remove later today. Maybe that will help!

    Since I have the Volvo valve coming anyway, I'm thinking of trying to drill out the closed end of the body and pressing out the pistons. Then tap and plug the hole.
     
  13. absostone

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    #13 absostone, Jan 12, 2023
    when i had mine apart i ripped a seal on the piston, and cant find the dimensions
     
  14. Dockboy

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    #14 Dockboy, Jan 12, 2023
    I'll get a picture and dimensions later today.
     
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  15. ragtop1

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    #15 ragtop1, Jan 12, 2023
    I asked Eurospares, but they don't have a rebuild kit. I'm going to keep asking other suppliers.
     
  16. absostone

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    #16 absostone, Jan 12, 2023
    Problem I found was that none of the mcMaster or grainger O rings were thick enough. I thinner one will still work and have no ill affects on the braking, Mine is ripped and occasionally the brake warning comes on. No big deal
     
  17. Dockboy

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    #17 Dockboy, Jan 12, 2023
  18. absostone

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    #18 absostone, Jan 12, 2023
  19. Dockboy

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    #19 Dockboy, Jan 12, 2023
  20. absostone

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    #20 absostone, Jan 12, 2023
    what car do you have?
     
  21. Dockboy

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    #21 Dockboy, Jan 12, 2023
    '77 GTB
     
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  22. absostone

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    #22 absostone, Jan 12, 2023
    [​IMG]
    Mine is like this one, strange yours is different. No pistons inside on yours
     
  23. Dockboy

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    #23 Dockboy, Jan 12, 2023
    Mine is like the one in post #11 & #17
     
  24. absostone

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    #24 absostone, Jan 12, 2023
    yup
     
  25. Dal308

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    #25 Dal308, Jan 14, 2023
    I ordered one of the Volvo ones new from IPD and it was less the 70 bucks plus freight. If that fits it's not worth the project to rebuild one. I believe the one on my 76 is the style with two pistons.
     
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