That already known shut off noise became constant even when the car is on

Discussion in 'Gen 2 Prius Technical Discussion' started by Brasa, Dec 4, 2021.

  1. Brasa

    Brasa New Member

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    All of a sudden that noise that the car makes when it is off became continuous from the moment I open the door until sometime after it’s off again. I noticed it comes from somewhere by the coolant. I’ve also seen other posts similar but confusing with different answers. Does anybody know how to fix it?

    Follow videos:

     
  2. PriusCamper

    PriusCamper Senior Member

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    Whatever you posted that's on Google drive is not visible to us... And can't make sense of what you mean when you say: "noise that the car makes when it is off became continuous from the moment I open the door until sometime after it’s off again."

    Has the noise always been there or has it changed in some way?

    I think you might be talking about the brake accumulator pump, or maybe the heat storage pump or maybe the sniffers that periodically check for leaks?

    In other words, you're gonna have to be more specific!

    You can also read your owner's manual to get an explanation of various noises.
     
  3. Brasa

    Brasa New Member

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    Sorry… I don’t know why the video won’t upload. I said it because the noise seems normal for a Prius as it was just regular in my car after shutting off, but then started to be more constant even when on and driving from the time I open the door until sometime after shut off. It sounds like this video but non stop intermittently.


    I must mention that there is no light on and brakes look fine. Car drives fine too.
     
    #3 Brasa, Dec 4, 2021
    Last edited: Dec 4, 2021
  4. PriusCamper

    PriusCamper Senior Member

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    Well, bleeding the air out of the inverter cooling system and brake system would be a good first step. The noises in the video are similar to those problems. Then once that's done you'll better be able to listen for what else to needs to be done.

    Also consider getting a device like this: Hybrid battery diagnostic and repair tool for Toyota and Lexus to keep in your glove box... It allows you to connect your phone to your vehicle via Dr. Prius app and you'll be able to read and clear error codes, as well as monitor the hybrid system. That way if bad goes to worse you'll be better prepared and less likely to get stuck waiting for a tow truck.
     
  5. ChapmanF

    ChapmanF Senior Member

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    If you mean the noise that sounds like a windup toy—the first noise heard in your video, before the other fans and such kick in, and again the first noise heard after your "one more time"—that is unquestionably the sound of the brake accumulator pump. It is that very distinctive sound and there is nothing else under the hood that sounds anything like it. There really shouldn't be so many different or confusing answers about it.

    It is normal to hear when you open the driver's door first time in a day. It is also normal to hear while driving, every few times you use the brakes.

    It is not very normal to hear that pump when you shut the car off, and that may be why some of us were slow to pick up on what you had in mind. If you were regularly hearing it when shutting the car off, your brakes have probably been in incipient failure for quite some time then, and recently it has just progressed.

    When somebody has a Gen 3, they face the puzzle of deciding which of two different assemblies they might need to replace for that condition, but back in Gen 2 those were combined into a single assembly, so you don't have to make any tricky call about what part is needed.
     
  6. Brasa

    Brasa New Member

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    Alright guys, thanks for clarifying. I feel now inclined to replace the brake accumulator pump. My only question now is whether bleeding the brake could be a possible solution/temporary fix, or is there really no way if not by replacing the whole unit and hurting my pocket.
     
  7. PriusCamper

    PriusCamper Senior Member

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    First step is to measure the time period between each time it runs... Once you can't go a minute before it turns on again you'll have been clearing warning lights for a while and will need to replace. Until then, just monitor it and once you have data on how often it turns on bring it back to this thread please.

    I'm still thinking you're worried about normal noises from your car as you've not clearly indicated anything to the contrary yet.
     
  8. ChapmanF

    ChapmanF Senior Member

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    If you have a pump that runs more often than expected when you use the brakes—say, it runs every time you brake, instead of every few times, which would be normal—then you might have an issue that the bleed procedure might improve for you, at least for a little while.

    If you have a brake pump that will repeatedly cycle even when nobody is touching the brake pedal at all—which is never, ever normal—then you have an issue that no half-measure is going to solve for you.
     
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  9. Brasa

    Brasa New Member

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    The noise runs every 10sec, and even when I am driving with my foot on gas. I asked about bleeding it because I brought my car to the shop not too long ago and I asked to bleed the brakes. However, they said it wasn’t necessary as the real issue was worn pads and a little lower fluid level; they topped off. Since I don’t have any lights on, I thought the problem wasn’t something major like brake actuator.
     
  10. PriusCamper

    PriusCamper Senior Member

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    You'd definitely have warning lights that can only be cleared very briefly if your accumulator pump is running every 10 seconds. If you don't have warning lights then the noise you're hearing is playing tricks on you...

    And as always the case, people with hard to understand noise concerns and no warning lights waste more diagnosis time then any other type of person. So for most mechanics, we'd prefer to think you're just crazy and know our day will go better if we avoid you rather than help you.
     
  11. Brasa

    Brasa New Member

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    I’ve seen other posts where this same issue didn’t bring the lights on with exact symptoms, so nothing unusual in my case. For what I understand not many mechanics know how to work on a Prius, which I’m aware, so they instead assume this and ask that until they pass it up. I think I was able to describe what it sounds and its period, and brake actuator does makes sense by how ChapmanF explained. I will order it.
     
  12. ChapmanF

    ChapmanF Senior Member

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    Do you have a laptop set up to run Techstream?

    You'd need that for replacing the actuator anyway.

    Since you'd need it anyway, you can also use it to watch the brake accumulator pressure live. If you see the pressure going up when the pump runs, and going down by itself even with no use of the brakes when the pump isn't running, then that will eliminate doubts about any noise playing tricks on you.
     
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  13. Brasa

    Brasa New Member

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    I don't have Techstream yet, but I will make sure to use it first as I just ordered. All I can tell is that it is the brake and the noise is incessant, and no, it is not playing tricks unless something else became severe. I recorded, but for some reason I am not allowed to upload so you could see it firsthand. If it helps to diagnose, my abs and brake lights briefly linger for a moment after starting up sometimes but they go off. I also recall sometime when the brake would fail when backing up slowly which would get me startled. I just really never paid attention because, like I said, there was never something major or lights on. Anyway, let's see if Techstream will tell.
     
  14. Brasa

    Brasa New Member

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    So I’ve run accumulator test and it did show the pressure going up and down all the time, non stop. It went from 3.3 to 3.6, and 3.19 when I pressed the brake. Does it confirm that I have to replace it?
     
  15. Another

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    Sure sounds like that’s the next step.
     
  16. ChapmanF

    ChapmanF Senior Member

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    Confirmed.
     
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