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A single clunking noise from the rear after each time the car comes to a stop

Discussion in 'Prime Main Forum (2017-2022)' started by leaftoprius, Dec 12, 2018.

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  1. leaftoprius

    leaftoprius Junior Member

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    In hindsight, my problem resembles even more tothe other post I mentioned in the original post.
    Prius "clunk" when coming to a complete stop with moderate braking | PriusChat

    That one turned out to be a problem with brake as well. Although the OP fixed himself (after the dealership gave him the run-around) and did not elaborate more on the details.

    Unfortunately, the dealership I went to have the organization structure that the customer facing folks aren't the actual mechanics. The "service adviser" writes up the service order. I thought I was lucky that they got a mechanics to test drive with me for less than 5 min in the parking lot without asking me wait or come back later. Given the run-around mentioned by the other poster in the referenced post, I was fully prepared not being able to get a test drive. Thus, I recorded the video/audio and prepared to show it to the service adviser and even text him the video if he needs it.

    I was rather surprised by the amount of time/tries it took to isolate the problem. I certainly appreciate their persistence. It could turn out much worse if they just gave it up and said problem could not be reproduced. At the end, I think/hope they fixed the symptom (and along the way fixed the problem). But the service report did not really go into the true root cause. True root cause analysis and trending are what allows a company to prevent occurrence of similar issue in the future. I assume those Technical Service Bulletin is probably a result of such analysis. I hope someone at Toyota quality is gathering all the warranty service records and plotting the trend.

    The hypothesis by SteveMucc sounds quite probable. In hindsight, the fact that the noise only occurs when the car comes to a stop, but does not occur when the car moving (even when over speed bump) probably points more to issue with brake than issue with suspension. It does sound like something in the brake is loose and raised when the wheel is still rotating forward/counter clock-wise (if using the driver side rear wheel as an example, the caliper is on the back of the wheel, 3' o'clock position when looking at the driver side rear wheel). Then once the car comes to a stop, that component is settling back down and making the knocking noise at that moment. Just a guess.
     
    #21 leaftoprius, Dec 15, 2018
  2. Since2002

    Since2002 Senior Lurker

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    Pads last so long on the Prius, and I would think even more so on the Prime since it can do more regenerative braking with the larger battery. So assuming they didn't grind that much off the pads they should still be good for a long, long time.
     
    #22 Since2002, Dec 15, 2018
  3. KrPtNk

    KrPtNk Active Member

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    If you have a problem in future, request the same mechanic. It might mean a bit of a delay, but he did good work and a request by name might be a feather in his cap. A friendly relationship built on mutual respect is what most of us dream of.
     
    #23 KrPtNk, Dec 15, 2018
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Probably no ID of the mechanic on the invoice, might be more than one.
     
    #24 Mendel Leisk, Dec 15, 2018
  5. SteveMucc

    SteveMucc Active Member

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    sure... I'm on my 4th Prius so I'm well aware of pad length (I've actually had pads out-last the bearings on a car (120K miles)). But that's not the point... the point is that they had a failure covered under warranty and they went and lessened the life of a disposable part as part of the fix without even asking if that was ok. Kind of a sleazy move. If it was bad enough to warrant resurfacing something tells me they removed a decent amount. And I hope that they used a purpose built machine to do it... if they sanded it by hand then there's no way in hell you're going to get the angle correct and until you wear the pad flat you're going to get less than 100% contact and less than 100% breaking force.
     
    #25 SteveMucc, Dec 16, 2018
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I think when they sand pad faces they're removing next-to-nil, just doing a quick roughening.
     
    #26 Mendel Leisk, Dec 16, 2018
  7. Since2002

    Since2002 Senior Lurker

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    You raise valid points if in fact they did substantially shorten the life of the pads through sloppy or over-aggressive sanding, or created future problems through incompetent work. But it's also possible that they removed very little material and did an overall good job. We just don't know. We also don't know if sanding the brakes was necessary, good chance it wasn't, but it sounds like the mechanic tried less invasive solutions first, and when that didn't fix it they spent time doing several brake noise mitigation steps, one or more of which appears to have fixed the problem. Yeah I guess they could have done each of the noise mitigation steps one at a time and test drove the car after each one, but they were chasing an elusive problem. And yes they could have added additional time informing the OP that they were going to sand the brakes and giving them an estimate of how many miles of reduced pad life that would result in. But if it was me I'd probably be like the OP and be happy with the service that they received, but each person has their own criteria which is how it should be.
     
    #27 Since2002, Dec 16, 2018
  8. SteveMucc

    SteveMucc Active Member

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    I personally would have let it go as well... but it would have niggled for a bit though...
     
    #28 SteveMucc, Dec 17, 2018
    Since2002 likes this.
  9. leaftoprius

    leaftoprius Junior Member

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    Well, the same noise came back again in less than 2 months after last visit the dealership. It seems like they did not fixed the root cause last time. I made another appointment to have it checked out.
     
    #29 leaftoprius, Feb 12, 2019
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