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Noise from brake, wheel bearing, or CV joint?

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by John Kuhn, Apr 17, 2020.

  1. John Kuhn

    John Kuhn Member

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    I have a 2017 Prius Two Eco, and it's been through three Wisconsin winters. This spring I've noticed a noise that I suspect is from the brakes, especially when driving in a parking lot in EV mode. It's a chirp-chirp-chirp, once every wheel revolution most likely. The front discs have a fair amount of corrosion in the area within about 1/5" from the outside edge. I'm a driver who tries not to brake hard, to maximize mileage, but the result may be brakes didn't get hard enough use.
    I set the park brake, jacked up one side at a time to spin the wheel to see if I could tell the source of the noise. Problem is it has to be in neutral to spin the wheel, and if you exit the car with power on in neutral, you get a very loud warning tone, plus another noise from somewhere under the hood, and it makes it hard to hear other stuff. Is there anyway to override the noise maker? Any thoughts on what I might be hearing?
     
  2. John Kuhn

    John Kuhn Member

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    Forgot to say the car has over 45,000 miles, and plenty of pad left on the front brakes.
     
  3. Tyfly

    Tyfly Member

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    With the warning sound, if you leave the key fob inside and then shut the door, it should stop the noise. Roll a window down just to make sure you don’t get locked out.
     
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  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Toyota USA recommends a fuller brake inspection (not just the 5k "visual" inspection), every 30K miles or 3 years. Try that first?
     
  5. bisco

    bisco cookie crumbler

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    any difference in d vs n?
     
  6. John Kuhn

    John Kuhn Member

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    Great idea, thanks, I should have thought of that!
     
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  7. John Kuhn

    John Kuhn Member

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    Yes, that's a good point. But I guess they would want to replace the rotors, am not sure I'm ready to go there yet.
     
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  8. John Kuhn

    John Kuhn Member

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    I only had it in N jacked up on one side, wouldn't be comfortable with D unless I had both front wheels completely off the ground.
     
  9. bisco

    bisco cookie crumbler

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    i meant when driving
     
  10. ChapmanF

    ChapmanF Senior Member

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    There will always be an outer narrow band of corrosion because the edge of the pad isn't all the way out at the edge of the rotor. It's not beautiful but it doesn't hurt anything, and isn't the cause of a noise (because the pad isn't touching it). There's also an inner band, beyond where the inner edge of the pad touches.

    It's when the narrow bands of corrosion start growing toward each other that there's an issue.

    In regular driving, the pads will scrub off whatever light surface rust gets on the braking area of the rotor.

    But in less-regular driving, those growing corrosion bands can get rough enough that they scrub away the pad instead:

    [​IMG]

    [​IMG]

    (Notice, in the top photo, the pad is munched away at both the top and the bottom. The profile photo doesn't show how deep the bottom munching is, because its radius doesn't reach the side edges of the pad yet.)

    If you have a jack, jackstand, and basic tools, you can do the kind of basic inspection that's needed to catch these things.

    There are options for dealing with the rotor if there is corrosion. Light enough, some 100 grit wetordry sandpaper and elbow grease can clean it up. Beyond that, it can be turned on a lathe, though in the aftermarket there are cheap replacement rotors these days for no more money than a typical shop charge for the lathe.

    If the dealer does it, they can use a lathe that attaches right to the car and cuts the rotor in place. Toyota recommends that because the surface ends up precisely normal to the rotation axis.

    You can also turn the wetordry sandpaper over onto a flat surface and rub the pad on it until flat again, if there's just minor munching of the edges and too much pad left to want to replace it. The wet paper will keep the dust down. Don't breathe it.
     
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  11. John Kuhn

    John Kuhn Member

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    Good stuff, thanks. The 1/5" I wrote was a typo, should have been 1", so a wider rust band I think than your pictures. I don't recall seeing any rust coming from the inner diameter. Haven't had a chance to get back to it.