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What causes rolling noise at low speed? Can it be this small link under car?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Jenny2010Prius, Apr 24, 2017.

  1. Jenny2010Prius

    Jenny2010Prius Junior Member

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    2010 Prius, about 110K miles. A few weeks ago, I started to hear a strange low rolling noise under the car, when drive from stop to go at low speed. Can't hear it after reaching above 20 miles/hr. It sounds like a metal ball rolling back & forth under. Hard to pinpoint where the sound comes from. Doesn't matter going straight or turn. No change when car is cold or hot. However, I can't hear it when slow down before stop, even in that low speed range.

    A friend had a look, and said there is a small link under the car, close to rear passenger side wheel, that is kinda loose. Holding the link and shaking it, there's some rattling sound. But we have no idea what this link is, and can it really be the cause of the sound I hear.
    small_link.jpg
     
  2. AzWxGuy

    AzWxGuy Weather Guy

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    That looks like a headlight leveler sensor for an HID headlight system. You have HID headlights? Yes, those ball-and-socket joints, and even the electronic bit which is just a rheostat that isn't sealed against the elements very well, can start making noises when corrosion has been working on them. Looks fairly corroded under there.
     
  3. Jenny2010Prius

    Jenny2010Prius Junior Member

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    Sensor? But there is no wiring out of it at all, and it's at the back side of the car. Rust, yes, that's the price we pay for city using salt on road in winter time.
     
  4. Unproductive1

    Unproductive1 New Member

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    It does look like a leveling sensor, I haven't checked what mine look like but judging from other cars I have worked on it looks about the same. The sensor is usually on both front and rear suspension, that way it can detect if the rear of the car is loaded down vs the front and aim the LED headlights down.

    It doesn't need to be stiff or tight it carries no weight.

    I don't think that is the cause of the noise.

    You mentioned you don't hear it when slowing down, I assume that means you don't hear it while applying brakes, I would check the front brakes
     
  5. fuzzy1

    fuzzy1 Senior Member

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    What is that thing in the upper right of your picture? It appears like an electrical connector and wiring harness, and is mechanically linked to the portion you circled.

    The leveling sensor is to compensate for weight in the back end, so is expected to be at the back of the car.
     
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  6. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Maybe get a dealership mechanic to test drive, see what they think.

    And yeah, that picture is the levelling mechanism for headlights, it's wired, and likely not the source of the sound.
     
  7. bisco

    bisco cookie crumbler

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    welcome!
    iirc, someone actually had a ball bearing rolling around in there car somewhere.
     
  8. Jenny2010Prius

    Jenny2010Prius Junior Member

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    Never thought it's a sensor, but now after reading what you said, it makes sense, too flimsy to be load bearing. Will take to a real mechanic to do a test drive etc. to figure it out. Thanks for all your kind replies!
     
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  9. bisco

    bisco cookie crumbler

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    please keep us posted, all the best!(y)
     
  10. Jenny2010Prius

    Jenny2010Prius Junior Member

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    Half year passed & finally confirmed what caused the noise - wheels! After changing all season tires (wheels actually - with rim) to snow tires, the strange noise totally disappeared. Looking back, the noise appeared right after changing snow tires to all season tires after winter.
     
  11. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    Nail in a tire?
     
  12. Jenny2010Prius

    Jenny2010Prius Junior Member

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    No nail or any obvious damage. Maybe wheel nuts were tighten too much, or not enough? Seems nothing to worry about
     
  13. NutzAboutBolts

    NutzAboutBolts Senior Member

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    Were the wheels balanced?
     
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  14. Jenny2010Prius

    Jenny2010Prius Junior Member

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    Balanced a few years back. Just occasional noise at low speed. No vibration
     
  15. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Can you clarify, was the noise tick-tick-tick, tied to car speed? Or sporadic.
     
  16. Jenny2010Prius

    Jenny2010Prius Junior Member

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    Kind sporadic & only at speed around 20 miles/hr. Those are alloy wheels if that makes a difference. (Winter tires have steel rims)
     
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  17. NutzAboutBolts

    NutzAboutBolts Senior Member

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    I wonder if there’s a rock in the tire on one of the wheels or somethings inside the tire o_Oo_O
     
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  18. Joabel

    Joabel Junior Member

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    I just had this problem. Took it to Midas and they found a pebble trapped behind the brake disk and had to disassemble the entire assembly to get it out. $130
     
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  19. AzWxGuy

    AzWxGuy Weather Guy

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    Pretty low mileage for a 2010. Makes me think of brake disk rust, but that usually only happens after it has sat for a while in humid or salt air conditions. The fix is to take it down the road, shift to neutral, and apply the brake. Do a couple cycles of this until the grinding noise is gone. This probably isn't what is causing it though. Thinking hub bearings and such, or some foreign body stuck where it shouldn't be.