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Strange Reciprocating Noise Sound under hood EV mode Gen 2 prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by KenP, Apr 10, 2014.

  1. KenP

    KenP Junior Member

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    I have a 2005 Toyota Prius. About a year ago it developed an intermittent noise under hood that lately has become more frequent. The gas engine does not have to be on for the noise to be present. The A/C does not have to be on. I have made a youtube video of the sound. Does anyone have any ideas about the cause? Thanks for your help.


     
    #1 KenP, Apr 10, 2014
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Make the Prius READY and open the hood. Look at the inverter coolant reservoir. Do you see fluid turbulence that shows the pump is running?

    Find the inverter coolant pump which is behind the driver's headlight assembly. Place your hand on the pump body, feel the pump's vibrations and see if that corresponds to the sound that you can hear.
     
    #2 Patrick Wong, Apr 10, 2014
  3. KenP

    KenP Junior Member

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    Patrick,
    There is coolant moving in the inverter pump reservoir.
    I found and felt the inverter pump. The car was not making the sound. I drove it for 5 minutes. It then started making the sound. I felt the inverter pump again. Although it seems like the sound is coming from the inverter pump area, I can't say that I felt vibrations on the inverter pump that corresponded to the strange reciprocating noise. I used a stethoscope on the inverter pump. Although this amplified the whirr of the flowing fluid, it did not amplifly the strange noise. The frequency of the reciprocating noise did increase while I was trying to track down the problem.

    Of note I did have the Recall Campaign A0N "Replace Electric Water Pump - Prius" done in Sep 2012. But I suppose the new pump could be bad, or perhaps the original pump was not actually replaced.

    Thanks.
     
    #3 KenP, Apr 10, 2014
  4. edthefox5

    edthefox5 Senior Member

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    Sounds like its down there in the ABS brake circuitry which is behind the Inverter down below. Or maybe the Inverter itself. Ok lets go through what we have to go through every time we see one of these. 20 questions:

    How many miles?
    Any dash check engine or mfd lights on?
    Car been in any accidents?
    Brake fluid low?
    Inverter coolant low?
    How's the brakes work?

    Sounds loud enough to just track down by ear though.
     
    #4 edthefox5, Apr 10, 2014
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I think that Ed has raised a reasonable possibility - that the brake actuator pump mounted to the firewall might be the cause of that noise. To gain access to that, you would first have to remove the cowl tray that the windshield wiper motor sits in.
     
    #5 Patrick Wong, Apr 10, 2014
  6. edthefox5

    edthefox5 Senior Member

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    Been a few reports of that pump failing. Hope not as its expensive.
     
    #6 edthefox5, Apr 10, 2014
  7. KenP

    KenP Junior Member

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    edthefox5,
    90875 miles.
    No check engine or MFD lights have been on.
    (Did a OBD-II scan using Torque app, no codes found)
    No accidents.
    Brake fluid full.
    Inverter coolant fluid full.
    Brakes working as usual.
    ...Ken
     
    #7 KenP, Apr 11, 2014
  8. KhaPhoRa

    KhaPhoRa Member

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    Coolant Control Valve, toyota part number 16670-21010 about $60
    If it fully fails it will throw a p1121 code. Mine did the same thing, it would throw a code for a day then clear then do it again. Relatively easy repair, definitely buy cable operated hose clamp pliers. I used this thread when I swapped mine out:
    P1121 - Coolant Control Valve Replacement (with pics) | PriusChat

    the Seahawks training facility ?
     
    #8 KhaPhoRa, Apr 13, 2014
  9. KenP

    KenP Junior Member

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    SOLVED ! Thanks KhaPhoRa. This is confirmed to be the source of the noise both by feeling the ICE coolant control valve and listening to it with a stethoscope. I will get the part replaced soon. Fortunately I have not had the P1121 error code yet.
     
    #9 KenP, Apr 13, 2014
    Patrick Wong likes this.
  10. KhaPhoRa

    KhaPhoRa Member

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    Glad to help. Don't worry too much about the code. From everything I've read (and dealt with) it's not going to hurt anything if it goes out, cabin heater might not work.


    the Seahawks training facility ?
     
    #10 KhaPhoRa, Apr 13, 2014
  11. cwerdna

    cwerdna Senior Member

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    I've intermittently heard mine make that same noise quite a bit while stopped (easiest to hear when the ICE is off). When the car was new, it didn't make that noise that frequently.

    I have no idea if it's doing it now as my dad's borrowing my car and I don't drive my Prius much anymore anyway.

    I guess now know what likely needs to be replaced if it throws P1121.
     
    #11 cwerdna, Apr 13, 2014
  12. KhaPhoRa

    KhaPhoRa Member

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    And just to add for future self-diagnosers out there: for me it was a much softer wee-ooh wee-ooh wee-ooh that I could barely hear, but the cadence was identical...


    the Seahawks training facility ?
     
    #12 KhaPhoRa, Apr 13, 2014
  13. bill02888

    bill02888 Junior Member

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    I'm having exactly the same issue! Hope that your resolution will work for me, too. Thank you for the post!
     
    #13 bill02888, Nov 9, 2017
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