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Weird grinding noise when regen braking

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by akh1685, Nov 5, 2014.

  1. akh1685

    akh1685 Member

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    The topic is as much as I can say to what my car's problem is.

    2010 Prius II with 50k miles now.

    When I'm slowing down and regen braking, I hear some weird creaking noise (imagine a metal bed frame squeaking -- sorry, this is the only noise that comes to mind lol). The creaking noise slows down as the car slows down. creakcreak creak creak creak..... creak.... creak....... creak............ stop. It's not a grinding noise that's constant. It's an interval noise that goes with the speed of the car as it slows down.

    I've tested the friction brakes (next paragraph) and had them checked, TWICE by the dealership I bought it from (Subaru; I will have a toyota dealership check when I have time), and they are stumped. All they can say is that my brakes are practically brand spankin new and the rotors have no rust/debris. Reason why I went to Subaru is because I have a 1 month warranty with them and I'd rather get my car fixed through that warranty, in which they cover 100% before I turn it over to a Toyota dealership -- if not, then Luscious Garage in San Francisco.

    When testing the friction brakes, I was rolling down a hill from 55mph and set it on neutral. Slowed down to a stop and there was no noise. Went up the hill again and did the same thing..... no noise.... until I put it on drive at around 15mph while braking, and the noise came back.

    I have a sound clip I will upload once I transfer it from my phone.

    But can anyone chime in and see what my car is suffering from? My 1 month powertrain warranty from the dealership I bought it from (Subaru) expired on the 3rd of November. I brought it in for inspection on the 1st. They claimed nothing was wrong. HOwever, this seems fishy. This noise is obviously bad. Are they supposed to use their ignorance card just because it's not a car from their manufacturer or are they supposed to make sure EVERYTHING is in WORKING CONDITION before they sell a car, new or used?

    Thanks.
     
  2. WilDavis

    WilDavis Senior Member

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    What happens when you use "B" for regen braking? (just curious…)
     
  3. akh1685

    akh1685 Member

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    The same thing that happens when on drive, actually. Noise. I recorded both N and D. I'll go out and record the B portion of slowing down to make sure it's documented.
     
  4. akh1685

    akh1685 Member

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    Ok, ran all tests.

    B produces NO NOISE when not pedal

    N produces NO NOISE when not pressing brake pedal

    D produces NO NOISE when not pressing brake pedal

    When pressing brake pedal:

    N produces NO NOISE
    B produces noise
    D produces noise

    Remember, this creaking noise comes from <25mph only. Very audible from 15-5mph.
     
  5. WilDavis

    WilDavis Senior Member

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    Bent rotors (front)
    Crud & dirt in rear drums (my Gen II (2009) has drums on rears which require cleaning out occasionally (every 100K or so…)
    just a couple of ideas… - Good luck! - Wil
     
  6. defrankond

    defrankond Member

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    My 07 had the same problem. Grinding type noise. The rear drums usually need cleaned and adjusted regurally. Especially after a heavy rain and such or driving on dirt roads a lot. Nothing serious though
     
  7. akh1685

    akh1685 Member

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    The noise I have only comes from the driver's side, front, wheel.
     
  8. sabasc3

    sabasc3 Junior Member

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    Hi akh, my 2011 Prius wasn't making the noise when I bought it almost exactly a month ago.
    It now makes the same sort of noise as yours, i.e. regen braking at low speed, a kind of a slightly undulating low-frequency "squeak", almost like my colleague's old office chair :D.
    In my case it's not very loud, easily drowned out by the radio. Same location: driver's side front wheel. I noticed that it didn't make the noise when it was raining this week.
    My suspicion is that the rotor's warped only slightly, i.e. not enough to cause a noticeable pulsation in braking but enough to cause the brake components to shift in sync with the disk rotation, and that two components that normally slide together (besides the rotor past the brake pads) may be making the noise. I'm thinking perhaps regen causes a force that alters the angle/magnitude of forces against the suspension or brake parts in a way that introduces the noise. Kind of like my colleague changing how the squeak happens depending on angle of chair, direction of leaning etc. I am also suspecting that water lubricates the squeak, so I might try squirting the caliper/piston area (a place where two parts must be able to slide past each other) with a spray bottle full of clean water, then drive around a bit and see if the noise changes or disappears.
    Scott
     
  9. Britprius

    Britprius Senior Member

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    The noise is likely to be one of the axle drive shafts CV joints "inner or outer". Under regen braking (braking in D or B above 7 mph) the braking load is carried by the shafts, and CV joints. When braking in neutral there is no regen and the normal disc brakes do the work so there is no load on the shafts, and CV's.

    John (Britprius)
     
  10. DaneH5

    DaneH5 Member

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    Gen IIIs have four wheel disc. No rear drums here.

    Are you able to upload sound files yet? My experience with CVs is usually a knocking noise and when turning sharply under load left or right should produce the knock for a bad CV joint.
     
  11. akh1685

    akh1685 Member

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    Thanks! This is exactly the noise I'm hearing. In fact. I had cleared things up with the Subaru dealership on my visit there today.


    My day ended pretty well today when I left the Subaru dealership. Although it took 3 hours of my time, 6 different people, including the GM... I have a scheduled appointment set to get my car worked on by Subaru.

    I made my case pretty loud when they gave me the real reason why they didn't work on my car in the first place, "our service department was going to work on your car to get the noise looked at, but sales didn't want us working on it and end up paying for it." I pointed at documentation stating my warranty that covers powertrain [INCLUDING BRAKES and parts that were serviced and replaced by the dealership prior to the purchase] and he got really quiet. I don't think he expected me to bring documentation and slap it in his face. 3 other customers waiting in line heard that comment and was furious and almost caused a riot inside the dealership because they, too, were having similar issues about cars being checked out 'fine' but still end up having defects after driving away.

    I had another test drive and it took 1/4 of a block to hear the noise and we were back in the garage that fast. I spoke to the GM and threatened them about bringing in an attorney to handle the dispute if they don't honor their warranty. GM says there's no need for that and he will personally take care of all my needs.

    Their promise? Fix the noise. If they can't fix it, send it off to Toyota to get it fixed. Will I get billed? Nope. Everything is in paper and still under their warranty they had given me. Typed up and documented.

    I was furious. But, at least everything is documented and I'll be having my car serviced this tuesday. Perhaps I can mention this CV part.
     
  12. Former Member 68813

    Former Member 68813 Senior Member

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    So, what is wrong with your car again? If only the ticking sound, I don't think it's really a defect, even though some people managed to get dealers to replace the drive-axles. I don't think I have that much argumentative power to even try. The mechanics in the dealership I use are pretty much deaf to subtle sound like that.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    May be this, not sure, but worth checking: I wonder if they've actually pulled off the calipers and had a good look at the inside of the rotors? The inside face is virtually obscured by the dust shield, when you do a simple visual inspection without some disassembly. This is what our rear rotors looked like, at around 46000 km:

    photo 4.JPG

    This is looking at inside face. Note the inside half is getting little or no pad contact, as evidenced by the rusty zone.

    After removing rear rotors and steel wooling, replacing rear pads, carefully positioning the piston cross pattern and reseating the pads, re-assemble and build up pressure before driving, they made a sound much like you're describing, for first day or two. Till the residual rust on rotors wore off, and the pads got seated.

    My take: the rear disc parking braking break mechanism is a poor design, can be compromised by less than ideal assembly technique. Specifically, there's a cross pattern on the rear brake piston, that needs to oriented to straddle a pin on back of inside brake pad.

    And the piston needs to be in firm contact with the pad, before the parking brake is engaged. Otherwise the piston may rotate on the pad. If the cross pattern can manage to shift up onto the pin, the inner pad gets uneven pressure, resulting in uneven contact on the rotor, which leads to rusting on a portion of the rotor. Per the pic.
     
    #14 Mendel Leisk, Nov 9, 2014
    Last edited: Nov 9, 2014
  14. DaneH5

    DaneH5 Member

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    From what I have read here only makes noise when in gear and braking, not when in neutral and braking.
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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    That's weird, cause it really seems from description of rhythmic sound, syncing with speed, to be rotor related. Puzzling.
     
  16. akh1685

    akh1685 Member

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    The noise, as I've read here and other forums, isn't a serious issue mechanically. However, it's not NORMAL. I shouldn't have to hear such noise coming from a car. Furthermore, I shouldn't have to DEAL with the noise just because it's a minor defect. Thus, getting it fixed is something I wanted done just because the 'what-if' factor down the line.
     
  17. akh1685

    akh1685 Member

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    View My Video

    Here's the sound clip. When I said, "right here", the noise was barely noticable because of the wind... but toward the 27 sec mark, it is very audible.

    Again, this was driving straight, no turning, between 20-5mph.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    That audio's very inconclusive for me, nothing standing out. ;(
     
  19. akh1685

    akh1685 Member

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    I know, camera phone audio sucks. But that's the best I can do. That was, btw, with windows up. With them down, the noise sounds much more like metal ticking.
     
    Mendel Leisk likes this.