Anyone replaced JUST the 'Brake Booster Pump' w/o replacing the (upper) 'Brake Booster'

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

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  1. davekro

    davekro Member

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    Brake Booster Pump (lower unit) Pic.png Brake Booster (upper unit) Pic.png I know the dealer and all repair videos say to replace both the Brake Booster Pump assembly (lower unit) -and- the Brake Booster assembly (upper unit), to fix the "C1391 Leakage in Accumulator" DTC code. Obviously, it would be a roll of the dice if replacing just one of the two units to save $600 on parts, risking your time/labor to go back in again, would fix the issue. I am curious of a few things:

    1) Would both units have a similar useful life? Meaning, if you only replace one unit, say the lower Booster Pump/Accumulator assy now and put the original Brake Booster assy back in, and you got lucky and the C1391 does not return in the short term, you should not expect the upper Brake Booster assy. to last another 220K (Gen 3's current mileage at time of this repair)? If likely not, then replace both and hope for another 220K before the issue might reappear.

    2) We don't know in a given Prius which unit caused the internal leak, or maybe a weak pump not producing enough pressure to spec. Is there any data to suggest which unit is most often the culprit?
     
    #1 davekro, Dec 3, 2024
  2. ChapmanF

    ChapmanF Senior Member

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    I've heard/read about a small number of cases where somebody replaced just the pump and s solved the issue in their car. More people give the odds the other way: if they're not going to replace both, they'll try just the actuator first. That's where most of the valves are that can the up leaking.

    It is just a matter of playing the odds: whichever unit you pick to replace, sometimes you'll turn out right. The odds just favor replacing the top one (the actuator). Or both at once, if you dislike a gamble.

    As far as expected longevity, it seems like the pumps can keep on ticking a long long time. But also, there are people who will let the problem go until it has the pump running every few seconds before doing anything about it.

    In a case like that, it's worth asking for how long the car was driven with, like, a year of 'normal' pump wear every week. The pump may not owe you very much after that. On the other hand, if the actuator got replaced not long after the first sign of trouble, the pump is probably ok.
     
    #2 ChapmanF, Dec 4, 2024
  3. davekro

    davekro Member

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    ChapmanF,
    Thank you for the informed perspective and context about my consideration to possibly replace just one of the two units. When I get the time to do the repair, I am leaning towards just replacing the upper Brake Booster. The idea that it has many valves, thus more potential places for failure, makes sense. Since my wife has now made clear that she does not feel safe driving her Prius in its compromised condition, it will remain parked until I can do the repair. I'll need to check if the Brake Booster is an in stock item. If it has a lead time, I'll order it sooner rather than later.
    Thank you again.
    Dave
     
    #3 davekro, Dec 6, 2024
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