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Prius V-Brake Booster & Pump Assemblies Failures

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Kenneth S, Nov 18, 2021.

  1. gromittoo

    gromittoo Active Member

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    Is it possible that @Tim Jones changed using a used part, that was never separated? I would consider buying a used combined part from a late 2015 or later Prius V, just to have on hand.

    Actually, I started to watch the video. In the video, the customer "Opted for a used unit", which came separated in two boxes. At least as far as I watched, no mention was made about new units being all in one piece, but the mechanic talked about purchasing them separately from the dealer for about $700 each.
     
    #21 gromittoo, Dec 20, 2021
    Last edited: Dec 20, 2021
  2. ChapmanF

    ChapmanF Senior Member

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    They're separate, as in, bolted down in different places under the hood. There is one steel brake line that passes between them (and a hose for low pressure connection to the reservoir).

    I would be surprised that you could even get them "together" from a junk yard. You'd be talking two large, heavy, bulky, obviously separate assemblies, hanging together by one flimsy steel brake tube, hoping to survive shipping, and that's what you would have to be calling your never-separated "part". And trying to remove them from the car or install them together like that would be a nightmare.

    The lower of the two units (the booster pump/accumulator assembly), per the original repair manual, was only to be replaced by dropping the subframe out the bottom of the car. When there later ended up being a recall on it, Toyota scrambled and manufactured weird-shaped single-purpose tools just to create an easier way to replace it.
     
  3. Georgina Rudkus

    Georgina Rudkus Senior Member

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    I guess Toyota is keeping the data as a "trade secret." I would like to know the percentage of the installed base has had a brake-booster failure.
     
  4. rjparker

    rjparker Tu Humilde Sirviente

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    Everybody I know with a gen3 has had a brake booster failure. My 2012 was the pump. On the other hand, no one I know with a gen2 , including my old 08, have experienced a failure.
     
  5. ChapmanF

    ChapmanF Senior Member

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    Has your 2012 also had a booster failure (the top unit here), in addition to the pump (the bottom unit here)? Or just the pump?

    [​IMG]

    From what I've seen, it seems to be the boosters more commonly, but not without exceptions.
     
    #25 ChapmanF, Dec 20, 2021
    Last edited: Dec 20, 2021
  6. rjparker

    rjparker Tu Humilde Sirviente

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    Both were replaced
     
  7. ChapmanF

    ChapmanF Senior Member

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    My sympathies.

    Were there proven problems in both, or was it a case of "just replace both and call it a day", or of the more frustrating "first replace one then find out it was the other"?
     
    #27 ChapmanF, Dec 20, 2021
    Last edited: Dec 20, 2021
  8. Georgina Rudkus

    Georgina Rudkus Senior Member

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    From Chap's posts of the YouTube video, it appears that there was a design defect an/or porous part in the alum casting of one of the components. The number of failures must be related with a certain lot run, until the casting was redesigned, It could be that not all of the castings in the lot were compromised by porosity.
     
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  9. ChapmanF

    ChapmanF Senior Member

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    Could you specify (or link) which video you're thinking of?

    I don't recall posting any video myself where casting porosity was suggested, nor can I remember encountering that suggestion before in anything I have seen or read about the brake issues. Maybe you were thinking of a video somebody else posted? If so, I'd be interested in seeing it.

    Or, maybe it was in a video I did post but I missed that point when it went by? That last one I posted was kind of long. Was there a particular spot within the video where you got the suggestion of casting porosity?
     
  10. Georgina Rudkus

    Georgina Rudkus Senior Member

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    The one in this post.

     
  11. ChapmanF

    ChapmanF Senior Member

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    Ok, where in the video, then?
     
  12. Georgina Rudkus

    Georgina Rudkus Senior Member

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    When he was starting the car and found that the booster did not retain the fluid, leaking and require the pump to keep refilling it.
     
  13. ChapmanF

    ChapmanF Senior Member

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    That is a common way that the 'booster assembly internal leak' issue manifests.

    But I have never seen it suggested before that casting porosity is the cause. So far, the best information that seems to be available is the NHTSA investigation titled "Brake Actuator Valve Wear". That's the hypothesis that has always seemed most natural to me as well; there are a bunch of small valves in there, and they get opened and closed a bunch of times in 150,000 miles, and they could either wear or become contaminated so they don't fully seat when closed.

    Regrettably, the petitioner who set off the investigation withdrew his petition, so the investigation got closed last January without giving us a final story.
     
  14. Georgina Rudkus

    Georgina Rudkus Senior Member

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    If it is found to be a design or materials defect, and since it is a safety issue that might cause an accident due to brake failure, there might be an unlimited recall on this item like the Takata air bags,

    By taking responsibility for the issue and repairing them at their cost, Toyota has avoided an investigation and a recall of all units. If this was to occur in the commercial aircraft industry, each and every unit would be replaced by the manufacturer.

    It would be likely that Toyota will be repairing these in secret way beyond the stated expiration date of their notice.
     
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  15. Tim Jones

    Tim Jones Senior Member

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    I was just kidding.............................
     
  16. gromittoo

    gromittoo Active Member

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    Silly me...
     
  17. nate358

    nate358 Junior Member

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    Is this the Break Booster leaking? I have a 2012 Prius v Five with 126,359 miles... I just replaced the rear wheel bearings, all 4 brake rotors and pads. I have been burning oil... And I saw a small leak that is now a huge leak while changing out the spark plugs. And from what I see I need to call Toyota today! IMG_4425.jpeg

    Posted via the PriusChat mobile app.
     
  18. ChapmanF

    ChapmanF Senior Member

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    No, that's a leak of engine oil.

    It might be leaking around the timing chain tensioner cover (that lozenge-shaped piece with the two nuts), which would be an easy-ish fix; you can buy a replacement gasket for that. If it is at that cylinder head to block joint instead, that's more of a challenge.

    In general, when you read about a brake actuator leak, it will be an internal one: fluid just returning to the reservoir instead of staying put. It is not typically the kind of leak where any fluid leaves the system.
     
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  19. Air_Boss

    Air_Boss Senior Member

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    That looks like a long-term leak. Spray it down with brake cleaner, and see where the seepage is occurring.
     
  20. rjparker

    rjparker Tu Humilde Sirviente

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    Could be the timing chain cover which is pretty common on these cars.
     
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