Run-run-run sound coming from rear

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by dhdfdh, Sep 6, 2021.

  1. dhdfdh

    dhdfdh New Member

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    A 2010 Prius with 92,000 miles. I've only had this car for three months and I can't say if I'm just now noticing this or it's always been there cause, with the AC on high all the time lately, it's more difficult to hear.

    When I start out, everything is fine, but when I get up to 35MPH, hear a run-run-run sound coming from the rear (I think). It's not excessively loud and, if it was a steady sound, you would think it was just road noise.

    It doesn't speed up or slow down as I speed up and fades into highway noise as I get past 50MPH though I can't say it disappears or just covered up by road noise. Once I get under 35 MPH, the sound goes away.

    Any ideas what that might be?
     
    #1 dhdfdh, Sep 6, 2021
    Last edited: Sep 6, 2021
  2. rjparker

    rjparker Senior Member

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    Probably rear hub bearings. You want Timken HA590373 or Toyota OEM as the cheap versions will fail quickly. They have abs sensors built in and can be difficult to remove diy. 23735F17-870F-48B8-A656-6D5FA45EDADA.jpeg
     
  3. burrito

    burrito Member

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    If it sounds like it's coming from inside the passenger compartment, it could be the HV battery cooling fan. It's designed to speed up and slow down in tune with car speed, so that the driver won't hear it. It's air intake is in the right rear.
     
    #3 burrito, Sep 6, 2021
    Last edited: Sep 7, 2021
  4. xliderider

    xliderider Senior Member

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    The fuel pump is under the rear driver's side seat area as well.

    Posted via the PriusChat mobile app.
     
  5. sam spade 2

    sam spade 2 Senior Member

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    How does that correlate with this statement that he made:

    I think it probably doesn't.
     
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  6. rjparker

    rjparker Senior Member

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    Wheel bearing rumble is common on these cars as they age. Any experienced mechanic can recognize the sound. Replacement quality is important as cheap units fail in months.

    Simple tests. On a downhill at 35mph let off on the gas to shutoff the engine. The wheel bearings will continue to rumble, a fuel pump will shutoff.

    For the battery fan hook up your fan control app and shut it off at 35mph. A wheel bearing rumble will continue. The fan will quit. Another test is to simply turn the battery fan to high while parked so you know what it sounds like.

    Finally jack up the rear and give the rear wheels a hard rotate. A bad wheel bearing will often make a low buzzing sound, a good one will be quiet. The wheel should rotate about three turns, a bad bearing will stop in one or less. Realize these direct tests are unloaded. A wheel bearing under load transmits vibrations through the suspension into the body creating the rumble.
     
    #6 rjparker, Sep 7, 2021
    Last edited: Sep 7, 2021
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  7. bisco

    bisco cookie crumbler

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    does it happen in ev and hv?
     
  8. dhdfdh

    dhdfdh New Member

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    This is a 2010. There's an app for that?

    I always drive in EV. I don't know what HV is. Is that Power Mode? If so, I want to say no, I don't hear it, but I need to check that when I leave in about an hour.

    If I don't hear it, what does that tell us?

    I wouldn't call it a rumble. Just say "run-run-run" out loud to yourself and that's what it sounds like.
     
    #8 dhdfdh, Sep 7, 2021
    Last edited by a moderator: Sep 7, 2021
  9. burrito

    burrito Member

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    You'll need a module which connects to the car's OBD port (the app talks to that).
     
  10. rjparker

    rjparker Senior Member

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    Dr Prius is probably the easiest to use app that allows you to turn up the battery blower. It requires a bluetooth obd2 module to interface to the car. You can also use it to monitor the battery temperature which could cause the battery blower to operate on high speed. It is also useful to review the hv (high voltage) battery voltages. There are several apps besides Dr Prius.

    I can tell you you can't hear the battery fan even on high unless the ac blower is less than half speed and you are not moving. Even then it sounds like a muffled blower. You would never mistake it for a wheel bearing that is easy to hear driving at 35-45 mph with the engine and ac on. Same goes for the fuel pump.

    A Prius hybrid, unless it is a plug in version, rarely runs on ev alone. It is constantly switching the gas engine on and off depending on the power required. At a stop the gas engine goes off. Going downhill or letting off the accelerator will turn the gas engine off. Most of the time you are getting some electric power and gas engine power combined.

    But everyone hopes for the easiest solution even if it does not make sense under the conditions described. In any case, the bluetooth obd2 module or similar linked below comes in handy for other purposes.

     
  11. dhdfdh

    dhdfdh New Member

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    Might this be the tire pressure sensor knocked loose?
     
  12. bisco

    bisco cookie crumbler

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    that would be a first
     
  13. xliderider

    xliderider Senior Member

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  14. bisco

    bisco cookie crumbler

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    that might cause a run-run-run sound
     
  15. burrito

    burrito Member

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    I suppose it could be tread separation. How old are your tires? When were they last rotated?
     
  16. drbtz

    drbtz Junior Member

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    Start from easy to hard. The way I'd go about it is as follows...

    1) Go to the rear tires and visually inspect to make sure nothing looks suspect (tread low, bubbles on sidewall, over/underinflated)
    2) Jack up the car in the read and spin the rear wheels by hand to ensure they rotate freely and don't make noise

    Those 2 alone should help you isolate wether it's the tires or something inside. Say those checks pass...

    3) Do the rj test, go up to speed with all blower accessories off, lift of the gas completely so the little EV symbol on the dash lights up. If it does and the sound is heard it's time to revisit the tires

    4) rj test passed, find out when the sound comes on. If you can sometimes get up to speed and not hear the sound it might be the hybrid battery fan

    5) So the sound comes on constantly, check the fan blower behind the glove compartment, make sure nothing has made it's way through the filter into the blower

    That's all I got for now unfortunately.
     
  17. rjparker

    rjparker Senior Member

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    Its the rear wheel bearings
     
  18. drbtz

    drbtz Junior Member

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    If OP is at all handy I believe they're bolt on which are easy to change.
     
  19. rjparker

    rjparker Senior Member

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    They are bolt on but often air hammered off as there is a press fit center piece housing the abs sensor that rust welds.

    C9B1794C-1A51-43B6-8A8C-B50F5E50F607.jpeg

    Possible Solution used by one member

    184FBEAD-4FB0-4048-9090-A15BA60EEEEF.jpeg
     
    #19 rjparker, Sep 8, 2021
    Last edited: Sep 8, 2021
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  20. drbtz

    drbtz Junior Member

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    That double wrench setup is brilliant.
     
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