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Brake Master Cylinder Failure

Discussion in 'Gen 3 Prius Main Forum' started by Shank, Aug 14, 2022.

  1. Shank

    Shank Junior Member

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    I have a 2010 Prius with 135,000 miles. Last year I changed the rear brake pads and a month later the brake master cylinder and brake booster failed and it was almost $2,000 to replace.

    When I changed the pads I did not bleed the caliper while turning the piston back into the caliper because I've never done that before in 30 years of doing my own repairs. Now I'm reading from some sources that if you don't bleed while compressing damage to the master cylinder may be the result.

    I know there is a history of problems with this part on the Prius including a class action lawsuit, but what is your opinion - did I cause the failure by not bleeding the caliper or is it just a coincidence? It has kind of been haunting me ever since.
     
    #1 Shank, Aug 14, 2022
  2. Tombukt2

    Tombukt2 Senior Member

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    Possibly but who cares now You've done put the 4K in the mess to fix it so. Or whatever it cost I just threw that figure out there I have no idea 2950 whatever. Hind sight generally isn't 20/20. I wouldn't have bled I would have just cracked dessert fitting at the offending caliper so as I screw the caliper down or squeeze it down the pressure I'm squeezing with my big 24-in pliers is not running back through the line to the actuator master cylinder and pump is squirting out dessert fitting on the ground on a towel or hitting the fender liner that way I know my pressure that I'm creating hasn't done anything except exit the caliper. I do that on cars that don't have ABS in actuators like before all that existed I always cracked the zerk that wheel. Watch the fluid exit on compression close the zerk .
     
    #2 Tombukt2, Aug 14, 2022
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Coincidence. No mention of this in the attached.
     

    Attached Files:

    #3 Mendel Leisk, Aug 14, 2022
  4. ChapmanF

    ChapmanF Senior Member

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    It wouldn't be easy to tell after the fact. That's pretty much why I open the bleeders when I shove pistons back. That way I won't be haunted later by an unanswerable question.
     
    #4 ChapmanF, Aug 14, 2022
    Tombukt2 likes this.
  5. PriusCamper

    PriusCamper Senior Member

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    But won't we always be haunted by unanswerable questions? Suspect it's the value of the human experience at such an early stage of our mostly malformed consciousness.
     
    #5 PriusCamper, Aug 14, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    I might be haunted by some other unanswerable question.

    Just not by the one about whether I knackered my $$$$ brake actuator by back-forcing old fluid through it.

    There are questions it's nicer to be haunted by than others.
     
    #6 ChapmanF, Aug 14, 2022
    Last edited: Aug 14, 2022
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