2012 Prius - New Calipers, Pads Still Dragging (hot brake discs)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by andreimontreal, Nov 17, 2019.

  1. andreimontreal

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    It was all about the caliper's cylinder not retracting.

    The Raybestols RL calipers that I got, both are not retracting properly. Either because somebody got in too much grease that's not of good quality and the piston slips on the O-ring. OR because the rubber they used in the O-ring is not doing it's job of flexing back - I don't know 100%. I'd have to play those a bit to see if I can figure stuff out.

    I think initially, the RL the oem caliper was literally seized from rust accumulation in the pins. I just discarded them not wanting to troubleshoot (you know, in the middle of a Canadian winter, with lots of things to do you kinda feel like saying "nope" when Rockauto gives you new calipers for 120 cad). So the caliper itself might've been good - I keep everything anyway, sorted out, because you never know - like now. I rebuilt it because I saw the boot was broken (an accident - most likely after I took it off as there's no indication of rust inside, I would say). When I measured it with the dial, after the rebuild, the numbers might've been wrong and I caught on this when I saw the dial seizing, leaving a space between it's tip and the cylinder. So I did tests by eye and it seemed to me the Tokico was working fine and I decided to use it and see if I'm right - and I was.

    A few more thoughts for future plans ...

    I will rebuild both calipers and I will use the Raybestos brackets for now (since they're doing a good job - the Tokico brackets are most likely pitted from rust, just like the pins are, and will damage my rubber bits so polishing a turd might not be a good idea - I think?? opinions?).

    I was planning to spray under the car with this special epoxy primer I heard of in the USA (Tamco - they have one urethane and a couple of epoxies which are supposed to be very good for encapsulating and protecting from rust for decades, car restaurers love them) so I should technically put a strong durable finish on those calipers when I get to do those cosmetic mods. Heck I am thinking of painting the whole car. I'll assess it to see how rusted it is - maybe I might wanna pick a newer thing for my projects; I got time to think about it anyway, I won't start until next year. And there's also the purpose it was bought for: mini van life mod.

    I'll finish that mod first (of course I'll share pics), test it out AND if they'll finally open those damn borders and let me down to FL that would be sweet. And then decide if I want a newer Prius, a hybrid Highlander or even a manual Civic hatch SI (did I offend anybody :p).
     
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  2. ChapmanF

    ChapmanF Senior Member

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    I have the sense that there is quite an unsuspected (by the uninitiated) amount of materials-science wizardry that goes into these things. One thing I noticed with the reman I bought was that it came with a much shinier piston: polished to a near mirror, unlike the matte grind on the Toyota piston. And I would not be surprised if that can affect the grip between the piston and seal. Not even getting into the possibility of using different elastomers for the seal, or the chance that a good grease for one elastomer is not a good grease for a different one.

    Then there's that groove in the cylinder where the seal lives: to the naked eye, it just looks like a square-cut channel, but that finite-element model from Delphi showed it as anything but, with a sloping bottom and an odd partial-depth spread that the seal can kind of lean into during brake application.

    [​IMG]

    ... but what's the shape that groove has after the reman shop is done with their sandblasting and honing and whatever cleanup of the bore they do?

    (I definitely noticed the reman I bought had blast texture on surfaces where the originals were machined flat, and even the reman I later bought from Toyota's reman program still had flat machined surfaces there. They must be more selective about masking before they blast, or about the condition of core they'll accept, or both.

    I suspect that the OEMs are thinking about a whole lot of those things, and the mass-market remanufacturers are just thinking about not such a lot of those things, and that for as long as I have the original parts in good enough condition to restore with the OEM kits, I'm inclined to keep doing that, rather than sending them down the core return chute where they will be crudely sandblasted and rattlecanned and show up at AutoZone.
     
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  3. andreimontreal

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    I noticed this type of negligence with aftermarket parts.
     
  4. Siward

    Siward Member

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    I have been driving on my LR Raybestos calipers for about year now with no problems. I left my winter tires on because I have been driving less than 4000km due to covid19 and it didn't make sense spending the effort to swap them.

    I will try taking pictures of caliper next spring if I finally swap off those winter tires. I am surprised you didn't fix this problem until now.
     
    #164 Siward, Sep 29, 2020
    Last edited: Sep 29, 2020
  5. andreimontreal

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    I couldn't fathom that a new caliper could be broken. When two new calipers happened to give the same issue I suspected anything but the calipers. Besides been busy enough and at home. You add all that up and months went by.
     
  6. ChapmanF

    ChapmanF Senior Member

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    That was more or less exactly the way it went with me too. I was so sure the fresh-from-the-box caliper I had just put on could not be the explanation that I was spinning all kinds of scary ABS actuator theories, buying 3000 psi pressure transducers and bleed port adapters, and trying to clear a spot on my calendar to try to track something like that down.

    And it was the aftermarket caliper I had just put on.
     
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  7. andreimontreal

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    I don't know whether to laugh or to cry, Chap. :ROFLMAO:

    Let me confirm again that I'm seeing some stupid low mpgs on my car - I got a reading as low as 4.2 l/100km (56 mpg) per one run. I'm getting my smiles per miles again. So that was my issue - and I'm still on winter tires still since I drove so little this year.
     
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  8. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    I think that's stupid high mpg, low litres per 100 km? ;)
     
  9. andreimontreal

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    Oh yeah - but 1 run of 10-15km : that's not the usual and I can get a heavy foot sometimes. On average, I still hit a bit lower than the advertised mpg. But that's the computer: I have to do the math on paper some day. Either way I wanted from 6.2L averages to 4.8L (say 5L) averages on board, so that caliper cost me a lot of money and time.
     
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