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Brake booster and master cylinder... Bleeding?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by bagn, Jun 8, 2022.

  1. bagn

    bagn New Member

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    I replaced the brake master cylinder and booster. I blead the brakes at each wheel. and I see there is a bleed point on the master cylinder.. So without tecscan how do I bleed it?

    Thanks !!
     
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  2. ChapmanF

    ChapmanF Senior Member

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    Without Techstream, you don't. (Strictly speaking, that's not quite true; there can be other scan tools, like maybe an Autel or a ThinkDiag, that also have the bleeding functions.)

    There are valves inside that unit you replaced that only open when the ECU commands them to, and without something like Techstream making that happen, nothing you do gets the air out behind them.

    If you are only bleeding brake lines (say, if you had simply replaced a caliper), you can get away with non-Techstream options.
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    I've attached with/without Techstream methods, from repair manual. I'm clueless, definitely defer to @ChapmanF : Techstream method is the way to go for this.
     
  4. ChapmanF

    ChapmanF Senior Member

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    Mendel has posted (it's happened before) with/without Techstream methods for brake fluid replacement. You can see that's the heading of those repair manual sections.

    The key to replacement is that you start with an already-bled system filled with fluid and no air, you let no air in during the process, and you end up with replaced fluid and no air. There is a non-Techstream method for that in the manual, as Mendel has posted.

    If there is air in there, as when the actuator has been swapped, you are not doing fluid replacement, you are doing bleeding. And because of the valves inside the unit that have to be commanded open for that to work, there is no non-Techstream bleeding procedure.

    Again, you can find some other scan tools that also have the bleeding functions. So I should really say there's no procedure for that "long-form" head-end bleeding that you don't initiate with Techstream or some other scan tool that can do it.

    If you are only bleeding lines out to calipers, that's easier.
     
  5. bagn

    bagn New Member

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    thanks
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    So if he goes with the Techstream method (as I suggested), he's ok? Or no?
     
  7. ChapmanF

    ChapmanF Senior Member

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    Yes, the Techstream brake bleeding for new actuator procedure is what does the trick.
     
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