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Brake Booster is going out, brought it to mechanic.. does this seem right???

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Stardustkarly, May 12, 2023.

  1. Stardustkarly

    Stardustkarly New Member

    May 12, 2023
    2011 Prius
    I can hear the accumulator/brake booster system (I don’t know the right terminology) re pressurizing every 15-20 seconds when parked and stationary. I took it in to the mechanic and they want to replace “both the Master Cylinder Brake Booster Assembly and the Brake Booster Pump Assembly”.
    Itemized with pricing is “Remove & Replace: HYDRAULIC POWER BRAKE BOOSTER-Master cylinder Includes: Bleed System” $1088 plus tax
    “Remove & Replace Brake Power Booster Unit-Accumulator” $1714 plus tax

    Does this seem correct? It is not clear if both are absolutely required, as it appears they are basing this off of “what Toyota recommends” and not which component is actually experiencing the issue. Unless it really is customary to replace both??
    Should I go ahead and let them replace it all or look around for cheaper parts?
  2. Tombukt2

    Tombukt2 Senior Member

    Nov 29, 2020
    Durham NC
    2009 Prius
    I have a 2010 JBL solar roof loaded car that's just started doing this and I'm going to start with the accumulator assembly apparently that house is all of the electronics that commands all the lights to come on for the most part then if it turns out that I have a hydraulic pumping issue from the pedal then I'll deal with the master cylinder or whatever they're calling that in this series of car usually from what I've experienced so far is something to do with that accumulator and pump assembly generally speaking so I'll hold off on the master cylinder that's just what sends some fluid over to the accumulator pump assembly and then all the computer start doing their thing and that's that.
  3. rjparker

    rjparker Tu Humilde Sirviente

    Jun 6, 2008
    Texas Hill Country
    2012 Prius v wagon
    On a 2011 I would change both. Some will say try the master cylinder alone but it is a lot of duplicated labor if you go in twice.

    These are known to go bad. Toyota changed them free for about ten years. They started that program with only one part but quickly defaulted to both because of come backs. Many including my 2012 v went out in five to seven years rather than twelve like your case.

    As a result it is very risky to go used since the remaining functionality of the used part could be short.

    Some used buyers get the wrong part because there are different part number versions per year and per model. The only way to know compatibility for sure is to crosscheck part numbers obtained from a vin lookup of the donor car and yours. Several have changed master cylinders two or three times because of this alone.

    I would go for the new master cylinder alone before going used.
  4. ChapmanF

    ChapmanF Senior Member

    Mar 30, 2008
    Indiana, USA
    2010 Prius
    Tombukt2 might be a bit mixed up about which parts of the brake system do what (or maybe I just can't tell what Tombukt2 is saying about it). Anyway, there are these two things:


    Note that both things have 'booster' in the name, making them extra tricky to keep straight. The bottom one is the "booster pump" (never forget to say pump!) and combined with the accumulator, and that's the thing making the noise you hear.

    More often than not, the reason it has to make that noise so often will turn out to be in the top thing (called booster in the picture, also sometimes called master cylinder and sometimes actuator, as it combines all those things) because there is much more action up there, around a dozen different little valves.

    Sometimes you'll get a successful repair by just replacing the top thing. Sometimes you can use a mechanics' stethoscope and hear a hissing, leaking sound in one unit or the other in between the pump runs.

    On the other hand, if it's been this way a while, making the pump run that often (normally it can go hours between, if the brake isn't used), that can have put a whole lot of extra wear on the pump and accumulator, even if the original problem was in the top thing. So that can be a consideration in favor of changing both.
    CR94 likes this.