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Waterpump stays on after car turns off. Killing 12v battery

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by zoeboi954, Jun 4, 2023.

  1. zoeboi954

    zoeboi954 Junior Member

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    Yesterday I came to my car to find out that the battery dead. So dead that I was having a difficult time Jump starting it. As soon as I got the jump I unplug the jumper cables and the prius immediately turned off and went into a limp mode that prevented it from going ready mode. So i figured the battery was dead dead. So I let the battery charge for about 15 minutes unplug the battery for about 2 minutes so I can clear the codes than it started.

    When I got home I turned the car off but I heard a slight hum coming from the engine bay. I pop the hood and located the noise was coming from the engine waterpump not the hybrid waterpump. It was weird because It wold turn on for a little than turn off than back on. And I can hear the relay clicking in the fuse box... I'm worrying because I don't want the pump turning on when the thermostat closes and burning it up. How do I fix this. I was thinking of replacing the computer box next the fuse box.
     
    #1 zoeboi954, Jun 4, 2023
  2. JC91006

    JC91006 Senior Member

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    What you're hearing is most likely the brake actuator, which is normal. I think you should just replace the 12v battery and then see if you have anymore problems.
     
    #2 JC91006, Jun 4, 2023
    Montgomery likes this.
  3. DirkAshburn

    DirkAshburn Member

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    Mine does the same thing - you can hear it while the car is running. Every ~10 seconds, it turns on then off. Repeat forever. After the car is off it does it a few cycles and stops. Have no idea how to fix it beyond trying to replace the thing. I don't know when it started, but its been like this for at least 8 months.
     
    #3 DirkAshburn, Jun 4, 2023
  4. zoeboi954

    zoeboi954 Junior Member

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    No it not my brake actuator I know what that sounds like. It's my waterpump. It sound like a small fan is on like a slight hum. The brake actuator makes a louder arrrgggh sound and that only last for a couple of second and it's done.
     
    #4 zoeboi954, Jun 4, 2023
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  5. JC91006

    JC91006 Senior Member

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    So you think it's the inverter water pump that's not turning off? Or the Engine water pump? Both of those should be changed by around 150k miles

    How old is your 12v battery? If it's 5 years old or more, I would just replace it and then continue your diagnosis and pull codes.
     
    #5 JC91006, Jun 4, 2023
  6. rjparker

    rjparker Tu Humilde Sirviente

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    I would certainly verify what the system thinks the coolant temperature is (not over 205f perhaps) to ensure that aspect.

    I would also verify the 12v under this condition.

    I would see if the first two relays below were sticking. Maybe just replace them. Otherwise it might be some sort of shorted wiring (unlikely) or a bad ecm. TIS has a test procedure but it is not specific for this condition.

    IMG_2136.jpeg
     
    #6 rjparker, Jun 4, 2023
  7. Montgomery

    Montgomery Senior Member

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    From what you wrote, its hard to tell if you had a old 12v battery that died and you tried to jump it and charge it ...........or...........you were having the water pump issue prior. From what I have learned here in Pruischat, jump starting a Prius can cause all kinds of electrical issues. I would follow RJparker's advice and see what your results are.
     
    #7 Montgomery, Jun 4, 2023
  8. PriusCamper

    PriusCamper Senior Member

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    This has never been an issue because the inverter coolant pump has to have the vehicle on to get power... I suspect you're referring to coolant heat storage pump, which normally but not always runs briefly after the car is shut off. Of course if your 3 way coolant valve has failed you might not of ever heard this pump and then if the valve came back from the dead briefly you would, which I suspect is what you're dealing with.
     
    #8 PriusCamper, Jun 4, 2023
  9. ChapmanF

    ChapmanF Senior Member

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    This looks like the kind of thread where the question on the floor is "which pump is that really?" and that should be a pretty easy question, either with a mechanics' stethoscope on the different pumps, or by looking for different fuses that serve the different pumps, and selectively pulling them.
     
    #9 ChapmanF, Jun 4, 2023
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