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. Kenny94945

    Kenny94945 Active Member

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    Wow... Interesting thread.
    What would cause drag/ heat?

    Un-true rotor
    Caliper pistons not retracting
    Brake pads too thick
    Pads not retracting on pins
    Caliper alignment
    Clogged brake line
    Emergency brake pads too tight or not retracting.
    Not sure if I missed anything.

    In quickly reading this tread the OP has looked at all these areas.
    I can only point out that the positioning of the caliper pistons is critical.

    Thinking outside the box:
    Maybe the axle is bent or something is bent?
    Maybe the rotors are not installing flat against the hub?
    As mentioned, maybe a wheel bearing or lack of lubrication is heating the rotor & caliper?
    FWIW, personally I am always suspect of aftermarket parts.
    Wield guesses: something with the ABS system, hybrid brake power generator, master cylinder, "B" position of shifter system (under the hood items or fuse boxes - something not in the wheel area you may not be paying attention to)

    Yes, six pages of investigation, so I can agree it may be time to go to a mechanic.
    OP, please let us know the cause :)
    Good luck.
     
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  2. andreimontreal

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    I'll write a book about it. Myabe I'll get my $$$ back.

    Now seriously - a couple of Qs to bounce back ideas:

    Un-true rotor: do you mean the brake disk is not co-planar with the brake pads? (you mention "the rotors are not installing flat against the hub?" - is this the same? I don't see how it would be different with my technical English). I did a comparative dial test and got nothing; I locked the disc in place with lug nuts and clamped the dial on the caliper's bracket - there should be a link somewhere.

    Then axle is bent or something is bent - it crossed my mind. How would I check this? I suppose only with those guys doing alignments or what? ... Looking in the sun the paint on the trunk lid doesn't seem the same and the rear bumper is suspiciously drooping, the eyelets on the bumper's edge are not firmly snapping in place around the rear lights (I will take it eventually off for a few things I have to do and I'll see what's going on underneath but I didn't notice this when I bought it - I want to make this car a travel conversion and I was looking to reinforce the rear like on a van and when I pressed on it a bit I noticed it starting to sag unusually).

    Maybe a wheel bearing or lack of lubrication is heating the rotor & caliper? How would a bad bearing feel when it's bad (assuming nothing else is touching the disc) ottomh when I did the test, the bearing felt quite smooth, is this something I should be able to feel by hand? When I spin the wheel I get something like 2.5 turns out of it. I'm thinking of doing the same with the caliper off to do a redneck bearing test, I reckon I should get at least 4 spins out of it with a good push, right? (Based on this old video posted, I think even in this thread).

    For the wild guesses, I did check with Techstream and it seems that under the hood everything works ok; the valves are closing/opening as per the repair manual.

    PS: I'm suspicious of 3rd party parts esp after this experience, but after all this, I'm starting to believe that Raybestos was really not the issue in this whole story given how messed up was the original Tokico; something caused that kind of a failure. In the future I'll stick with oem.

    I'm looking online and I can get an oem bearing assembly for about 210 cad - shipping/taxes in. If anybody has pointers for ruling the bearing out ...? now is the time. I wanna do the "ramp it off a cliff test" (kidding - I won't).
     
    #122 andreimontreal, Sep 10, 2020
    Last edited: Sep 10, 2020
  3. ASRDogman

    ASRDogman Senior Member

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    It's might be possible the hub is bad. But I don't think it is the cause of the problem.
    If it was to get that hot, you would be able to hear it, yes, hear it. It would be very loud
    as you drove. And spinning it without the caliper on, you'd know it was bad, and be able to feel it.

    If something was bent, you could probably feel it as the car would likely pull to one side as you drove.

    How do they pads look? Are they wearing evenly? I believe you've already read about where the
    puck has to be in a correct place so the two pins on the pad can fit inside the puck properly.
    Easy enough to double check. Also, doubtful you would get 2 calipers that were sticky with so much
    time between purchases.

    This one is a real stumper! Hard to trouble shoot in a chat room.
     
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  4. Kenny94945

    Kenny94945 Active Member

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    I really think you need to bring to a mechanic.
    As ASR wrote above, "This one is a real stumper! Hard to trouble shoot in a chat room."

    A) As for your un-true rotor question.
    The rotor itself, where the pads grab, may be wrapped.
    I believe the OP stated they used a dial indicator tool to check rotor "run out".
    Typically this wrapping can occur from heat or if the rotor was dropped and damaged
    B) Flat against the hub.
    As you install the rotor over the lug nut studs the rotor should sit flat again the hub.
    Some times there are "push on retainers" (that hold the rotor to the hub) that are mis-installed and cause the rotor to not sit flat.
    A straight edge tool can be used to insure both meeting surfaces are flat (rotor to hub/ rim to rotor)
    C) Bent Axle
    That should be easy to see by eye by rotating the axle assembly.
    Your dial indicator could also be an aid.
    You could remove the axle to be 100% certain, but I think that is not necessary if A & B test true.
    D) Something else bent.
    Uh oh, OP writes about mis-aligned panels.
    They may not know the car's history, but this brake heating issue is new?
    Yes, a frame shop visit will ensure the car is straight and really the best way, as compared to using strings and ruler in a home garage.
    An alignment shop would be able to to show caster which could be an indicator of something bent.
    Toe and camber may not be as valuable a report as caster, but even then, wheel alignment is a static measurement and the issue is cause from rotation.
    E) Bearing
    Yes, should be able to feel by hand.
    Remove for true inspect if you wish.
    And don't forget to inspect the bearings race surface nor install the bearing to tight.

    BUT....you need to take this to a shop.
    This chat room discussion is not working to find your issue.
    My take is the OP has ruled out almost every mechanic possibility and I am again led to my comment about the ABS, "B" power, or other electrical/ computer issue.

    Again good luck.
     
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  5. andreimontreal

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    Update troubleshooting for the bearing - the bearing is good: Without the RL caliper on, the RL wheel spins 8-9 times smoothly - no issues there. With the caliper on I get 1.5 turns maybe. The good RR wheel gives me 2.5-3 turns in comparison. Next.

    Now, I remember, when I changed the caliper the first time, I stupidly pressed the brake with the caliper off the disc and I spilled the brake fluid emptying the main cylinder. I found a technique where you route the bleeder back into the brake fluid container and bleed like that until there are no more air bubbles showing. I thought things were good BUT I'm thinking that it's possible I did a poor job and some air is stuck inside.

    @ASRDogman The wear on the pads for RL wheel - not sure how normal is that, seems to be a slightly uneven wear so I measured all the corners of a pad to make sure I get the whole picture. I pinched the whole pad to be faster more accurate with the calipers, there's about 7mm on the pad (btw, (y) always checking that the cylinder seats flush on the pad, ie not riding the pad's pin):

    Outer Pad: (seems oddly uneven)
    13.10 - 14.16 (Top bleeder side - Outside Of the Disc then inside of disc)
    13.47 - 14.51 (Bottom Outside - inside)

    Inner Pad:
    14.10 - 14.10 (Top Outside-Inside)
    13.65 - 13.81 (Bottom Outside - Inside)

    Other than that I'm all out of ideas. Either way I think I'm going to the mechanic next.
     
  6. andreimontreal

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    Somebody mentioned TIS "brake relearn" at some point somewhere, I forget. Is that a thing? Do you do it with a regular bleeding in TIS or how does it work? what should I look for in TIS?

    I tried some google'fu and found: "Bleeding without the Techstream may result in air remaining in the brake hydraulic system." (in here) So by deduction, the Techstream bleed should take care of any potential air locked in the system?
     
    #126 andreimontreal, Sep 12, 2020
    Last edited: Sep 12, 2020
  7. ASRDogman

    ASRDogman Senior Member

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    Air in the system will not cause the caliper to stick. It will give you a a mushy pedal though.
     
  8. andreimontreal

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    Ok. Also, I imagine when they changed the booster they must've ensure there's no air trapped in there?

    Gonna play with Techstream to see if I can find any re-learn info in there - my last resort.
     
  9. ChapmanF

    ChapmanF Senior Member

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    Air in a conventional system has predictable effects, like a mushy pedal.

    Air in a system like the Prius has can be less predictable. For one thing, it doesn't necessarily make the pedal mushy. Your pedal input is just an input to the computer, which then decides on a target wheel cylinder pressure and makes that happen. If there is a bubble in the line, the computer just holds a valve open some milliseconds longer to let more fluid in there until the bubble is compressed to the target pressure. You don't get a different pedal feel (though you might notice more of a squirty sound). When you release the pedal, the fluid should be allowed back to the reservoir and the bubble springs back. You might hear a squirty sound then too. As long as enough fluid returned and the line pressure returned to zero, I would not expect it to create a brake drag.

    In case of an event that drops the brakes into fail-safe mode, you may then discover to your surprise that the pedal is all mushy, perhaps mushy enough to preclude stopping the car. So even though the normal operation of the system can kind of mask a problem, it is very good to bleed all the air out.

    Techstream offers two bleeding procedures, one for routine use after working at the wheels, and a more thorough one for after replacing the actuator or accumulator, or after any accidental intake of air through a low reservoir level.

    If there's any doubt about what's in the passages up there, that's the procedure to use. It takes a while to do, so the 12 volt battery should be very well charged before starting, or supplemented, or both. The cowl should be removed in advance for access to the stroke simulator bleed screw. Techstream will direct you to bleed from there at the appropriate moment, which is not when you want to say "oh heck, it's under there?" and go gathering wrenches.
     
  10. Ed Beaty

    Ed Beaty Active Member

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    A thought. Rear caliper piston orientation. Mentioned in passing above, but not confirmed by OP:
    When assembling the REAR calipers, are you sure that the piston was rotated so that it was oriented thusly:

    Screen Shot 2020-09-12 at 9.49.46 AM.png

    This is critical; the back of the brake pad has a small pin which must be located in the opening in the 'X' of the piston for proper operation.
     
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  11. andreimontreal

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    Chap ... (y)x1,000,000 - I was reading in the manual and wondering about this. The manual puts 1 to regular bleeding and 2 for system bleeding - not that it makes sense but I better as as a just in case: are these steps to each other, should I do a normal bleed if I want to do a system bleed?

    I attached the regular bleeding and "brake system bleeding". Also cowl removal procedure for 10-15 Priuses in case somebody else needs this.

    I would think Toyota did the system bleeding when they changed my booster . I'll remove the cowl, if I have easy access to the stroke simulator bleeder then I might give it a shot just to make sure (maybe ???). I got interrupted today from all this - it seems I'm the only one with 2 right hands in the fam capable of building.
     

    Attached Files:

    #131 andreimontreal, Sep 12, 2020
    Last edited: Sep 12, 2020
  12. andreimontreal

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    After I'm done torquing, I depress the brakes and stick my head in there to make sure the piston sits flush (literally). Been checking this since day 1, and I always make sure it's not part of the error - I've mentioned sometimes that I make sure the cylinder is flush, not riding the pad's pin. Every basic brake installation procedure is respected surgically ;) (I can be a maniac with making things pretty and respecting norms).
     
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  13. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Also don't apply parking brake till after a test drive, then apply/release it several times, raise the rear, and spin the wheels by hand; verify there's only a slight drag, they'll easily turn 2 or 3 revs with a good push.
     
  14. andreimontreal

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    @Mendel Leisk - I rarely apply the parking brake.

    Both the mechanic and Toyota said it must be the caliper. My mechanic said I was troubleshooting it well and said to check the pad brackets to make sure the V clips are pushing out the pads. I checked for rust behind the main bracket, and made sure the stainless brackets were letting the pads slide out easily and still got heat.It did feel like the wheel was turning slightly easier, but when turning the rotor by hand it was still a drag.

    I'd have to replace the calipers according to them, and I can't help but wonder if I buy Tokicos and it's not that - then do I do?? The Toyota rep said he saw a similar situation and it was solved by changing to the Tokico - but I keep having this feeling it might be something else: just because the original seized caliper was in a really bad shape and now tow calipers malfunction exactly in the same way 1 year apart on the same side.
     
  15. ASRDogman

    ASRDogman Senior Member

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    It would depend on how many miles you drove, How hard/light you are on the brakes.
    And the quality of the caliper. If they just "rebuilt" them, they only cleaned it up and put new seals
    inside. If they "remanufactured" it, they honed out the cylinder, new puck, new seals.

    Didn't you have problems with one set of calipers and had to get another set?

    Well, you could purchase the calipers that they said to get. Or, take the ones you have now apart,
    sand down the cylinders with fine sand paper, clean them good with brake cleaner. Put them back
    together and how they work....

    Not and easy decision....

     
  16. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    If the rear is raised will the wheels free-spin with a push, 2~3 revolutions? If not something is fundamentally amiss.
     
  17. andreimontreal

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    It's the same case ASR :cool:. Just look at the list of things I've done. That's why I'm going insane. RockAuto just sent me a warranty replacement and it's doing the same thing (for rear left - I didn't even to take off rear right which is fine.


    Before I did this bracket check, RL was giving me 1.5x ish turns and RR (The good one) si giving me 3 turns. The RL however, it seems it has improved (like I kinda get more than 2 turns, but if I take the wheel off it still feels hard to turn the assembly by the bolts - vs RR which is fairly easy) . I have put back in the same old pads and rotor, I didn't want to put in the new pads and rotor until I got no heat.

    I get this issue down to the caliper indeed. But is it the actual caliper? OR the fluid? And the fluid doesn't come out when I open the bleeder. So yeah, it looks like it's the caliper.
     
    #137 andreimontreal, Sep 22, 2020
    Last edited: Sep 22, 2020
  18. andreimontreal

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    I took the OEM calipers apart (kept those in a box for days like these). The rubber parts look good. Gonna try to clean the RL and bolt it on the Raybestos bracket.

    Overall there are tiny details which shows that the Tokico are meant to last. Also reading on some trucking forum that they have trouble with Raybestos/Chinese calipers breaking easily/too soon. Tell people to get OEM at all cost when you see their posts. My Raybestos discs with anti-corrosion had corrosion spots after winter - not right, I think.
     
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  19. ASRDogman

    ASRDogman Senior Member

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    Make sure they are SUPER clean! NO burs.
    I know it's a PAIN! And stressful, because it doesn't make sense. Check everything slowly,
    and carefully.
    Since they are the rear calipers, how is the parking brake? Is it catching? Too tight?
    Is the cable rusted? I don't remember, but have you disconnected it and drive it?
    If so, does it still get hot?
     
  20. andreimontreal

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    I disconnected it, drove like that, and still hot. Not the cable by far. The cable has the tip rusty but inside it was lubed (the rubber boot comes off if I pull too hard just like on a caliper).

    Cleaning does make sense! I know I don't wanna damage that square rubber ring. Yeah, I've watched caliper reconditioning clips, I'll make sure they are surgically clean. I have to scrub the caliper with a wire brush first before I can begin.

    The parking brake, if you refer to how the pedal in the car feels, it is loose because I loosened it way way back. The one on the caliper is springy, hard, seems to be in good shape (both the one inside, and the one outside - there are 2 springs).
     
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