Brake booster & accumulator issues

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by NYPrius38, Dec 15, 2024.

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  1. NYPrius38

    NYPrius38 New Member

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    new york
    Vehicle:
    2012 Prius
    Model:
    III
    I brought my 2012 to a dealer for diagnosis since the brake, ABS and traction control lights were on. They diagnosed: "internal failures within the brake booster assembly with master cylinder & brake booster pump assembly due to age and mileage (242k). Technician also found excessive leak in the accumulator. Recommend replacement of brake booster assembly with master cylinder, pump assembly and brake booster."

    Ok, so the day before my appointment, all the lights went off and the car drove normally. Well, normal being the pump running every 5 seconds and its been that way for about 50,000 miles. For about 20,000 miles, the brake actuator makes noise when stepping on the brake too hard. So, I know there are problems. I declined the $4200 repair (including EGR replacement) and the lights went off for a week. Back on for a few days and now they've been off for 3 days. Aside from the actuator, this feels more like and electrical short, bad sensor or some other issue. The pump is fine because it is constantly running. Cruise control still works when the failure lights are on. I just don't know how/why the car isn't having these failures 100% the time if all these items need to be replaced. What does the community make of this? Thank you in advance.
     
    #1 NYPrius38, Dec 15, 2024
  2. Tombukt2

    Tombukt2 Senior Member

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    I don't think the pump is fine because it's constantly running It's working and constantly running and I don't think that's how it's supposed to be so there's always that It's not supposed to be constantly running It pumps up this tank that holds brake fluid under pressure. And then the pump shuts off and then when you step on the brake and bleed that fluid down out of that accumulator the pump comes on to pump it back up this is basically what works your brakes I mean if the pump is running all the time then it would seem to me the accumulator is not able to store the pressure and the pump is constantly running to try and keep the accumulator at a given pressure and that's not acceptable I don't think.
     
    #2 Tombukt2, Dec 15, 2024
  3. ChapmanF

    ChapmanF Senior Member

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    Needing to run every 5 seconds is far from fine. Some people do seem to want to put off replacing the actuator for the longest possible time, but at every 5 seconds already, you know that time is coming. (Or, some would say, already here.)
     
    #3 ChapmanF, Dec 15, 2024
    Tombukt2 and Brian1954 like this.
  4. NYPrius38

    NYPrius38 New Member

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    Dec 13, 2024
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    Location:
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    Vehicle:
    2012 Prius
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    III
    Ok, I get it. I know this isn't "fine". What I was really looking for an answer for was why is this part of the car running ok and other times, the dashboard lights are all on. Then they go off for a while and I feel safe to drive it because I have ABS and traction control again. Obviously the parts aren't fixing themselves, I'm just looking for a little insight.
     
    #4 NYPrius38, Dec 21, 2024 at 11:18 PM
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