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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    Ok, this is bad. Replaced seized rear calipers with new Raybestos, new discs, new pads, changed the fluid, bled it. The rear still drags. The right rear has a 1/16" (edit: at most, I over reacted with the first value) blue ring at the inner side of the disc from high temperature.

    What could be wrong? Bubbles on the line? The parking brake line pulling - is that possible , is it even adjustable ?
     
    #1 andreimontreal, Nov 17, 2019
    Last edited: Nov 17, 2019
  2. ASRDogman

    ASRDogman Senior Member

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    There is a cable you adjust from under the dash on the pedal I believe.
    I've never done it, but I read it here. :)
    With the new pads the cable probably needs to be loosened.....
     
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  3. andreimontreal

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    Thansk ASR, looking for it now.
     
  4. spiralhelix

    spiralhelix Member

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    I agree with the e-brake as the first to try.

    When you twisted the piston in, is it possible it just didn’t go in as far as it could?

    One time when I did my front brakes, after I pushed the piston all the way in, everything was very tight on one side. The other side was fine. For a week I only did short little trips, 5 min at a time until it loosened up. That was 75k miles ago and brakes are still in good shape. No rotor warping or anything. So I chalked it up to either the pads were just a little thicker or the rotor was. I think the manufacturing date was a Friday afternoon ;)


    -Spiral
     
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  5. spiralhelix

    spiralhelix Member

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    Technically, the repair manual says you need to release the e-brake cable first. Then at the end you reassemble and use that nut adjustment for desired travel.

    Just as a future reference.


    -Spiral
     
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  6. andreimontreal

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    SO - I opened the dashboard at the left of the steeringwheel and adjusted the nuts outwards by maybe 1/8" in total. No change.

    I have to grab the right-left rotor with by two bolts with two hands. Rotating front it sticks occasionally and it's hard to rotate. Going backwards, no sticking, and hardly rotates. I know it should rotate, scrape a bit but move freely.

    EDIT: rotor spin - mine ain't like that, way harder, need two hands

    My mpg went from 5.5l/100km to about 7; at least that is a strong tell tale sign. At times it drops towards a 5.5-6l/100 after 50-70 km if driven in the same day. Gonna go bleed the brakes and see if that helps. Post ideas if anything pops in ur head.
     
  7. spiralhelix

    spiralhelix Member

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    I’d go loosen that nut further and remove the tension on the caliper, push the piston back in again with the brake line clamped and a brake bleed bottle connected to the bleeder. That will ensure you get the piston all the way in. The reassemble everything and try rotating. If that’s good, finish up with the e-brake pedal and adjust the nut. I’ll check the pages in the repair manual and report back.


    -Spiral
     
  8. spiralhelix

    spiralhelix Member

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    pages 1220-1224 in the repair manual...but here they are:
     

    Attached Files:

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  9. spiralhelix

    spiralhelix Member

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    oh, it shouldn't need mentioning...but some like to nit-pick...obviously ignore the parts relating to the axle hub assembly and/or the speed sensor if you don't have one.
     
  10. andreimontreal

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    I think I got it - but not 100% sure. I bled the rear brakes again and there were a few bubbles coming out. After that it felt as if the wheel was a tad bit looser.

    However I noticed something bad: the wheel is free for the most part but it sticks in certain points 1 or 2 spots when moving it "forwards" by hand using a bolt. The backwards rotation seems to has no such sticky points. Could it be warping? The disc is tilted? I'd like to believe it's some old rust underneath making it sit uneven. I think I should take it off and clean the hub better?

    EDIT: I forgot one thing. The caliper wasn't moving along the pins - I think it was the bubbles. But I forgot to check it after to see if it's loose after I bled it. I only tried the rear right one. It couldn't be seized, it's new, lubed with silicone grease.

    Also, what's the surest way to ensure that there's no bubbles left in the system. When I changed
     
    #10 andreimontreal, Nov 17, 2019
    Last edited: Nov 17, 2019
  11. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Are the caliper pins lubed? Sil-Glyde Brake Lubricant works.

    Did you pay attention to the brake piston orientation, should be thus:

    upload_2019-11-17_21-53-48.png

    And well seated against the brake pad. If the piston is not oriented thus, or manages to rotate, you will have steady drag. Properly adjusted, there should be just a slight amount of drag:

     

    Attached Files:

  12. andreimontreal

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    Hey Mendel: yes I greased with AGS sil-glyde, everything is new and I made sure the piston was rotated like that with the cube and whatnot - you guys were diligent about letting me know about that (awesome forum!).

    I had one issue during the uninstall - a caliper leaked and at some point the liquid got low in the reservoir and I wasn't sure if I got air in or not. I pumped minutes/hours cycling fluid in closed circuits (without any line being able to suck air in) until I saw no more bubbles and making sure the liquid never went low in the reservoir. I had an assistant pressing the brake and I must have cycled a 1 to 3 quarts in this process, of course reusing fluid - I don't even know, I cycled hoping any stuck bubbles would come out. At times there were very few fine bubbles but I said I'd let the system sit and bleed them in a week or so (that was now). So that's why I narrow it down to bubbles as one of the potential main culprits.

    My dad cleaned the rust off the rotor with steel wire brushes and a drill - it looked good. So I'm not sure if that disc would have a chance to sit slanted so not sure about the stickiness that I mention.

    Other than that, things look great; I have no further clue of anything being broken. Thanks for the clip - I'll hoist the wheels again and give it a spin tomorrow.
     
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  13. The Critic

    The Critic Resident Critic

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    Things that come to mind:

    1) Are the parking brake cables moving freely? They may be seized.

    2) Remove the caliper and make sure the piston is lined up correctly. If the piston is not lined up perfectly (there is a very small window), the pads will drag.

    3) The calipers may be defective. All of the reman calipers on the market today are of questionable quality.
     
  14. andreimontreal

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    They're not re-manufactured according to the website "Unlike traditional calipers, Element3 calipers by Raybestos feature all new components, combining optimal performance with time-saving, trouble-free installation." BUT, I wouldn't rule out the possibility of having a defect caliper.

    As for 1, when I took them off and put them back I saw under the rubber boots that the line is dowsed in some grease o some sort. I'll go over the repair instructions but I doubt it.

    For 2, when I installed I rotated them and I thought I paid careful attention for one of those Vs to open downwards to hug the pin - gain, I'll take a look just to be sure :confused:.

    ###################################################

    QUESTION: Could too much of that sil-glyde cause any issues? When I installed I rubbed and pressed and made sure there's no vacuum and whatnot ... but I'm wondering.
     
  15. The Critic

    The Critic Resident Critic

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    It is not related to the grease.

    So new chinese calipers? Not sure if that's better or worse...

    Try disconnecting the parking brake cable and see if the drag changes. If there is no significant change, the issue is with the caliper or the hose.
    To rule out the hose, loosen the bleeder screw and spin the wheel.
     
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  16. andreimontreal

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    Unhinging it at the caliper?
     
  17. The Critic

    The Critic Resident Critic

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    Yes


    iPhone ? Pro
     
  18. Siward

    Siward Member

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    I am not an expert here. I vote for #1.

    Since the caliper is new and it is the rear, my best guess is an over-tensioned parking brake line. Or somehow the parking brake lever on the caliper is stuck pulled down. It is like driving with the handbrake on.

    You can rule it out by simply detaching/unhooking the parking brake line from the caliper and ensuring the lever is in the fully up position. Make sure that lever spring is working to keep the brake open when no tension is applied. Fasten down the parking line, then test it to see if it is still getting hot after retracting the piston. If it works, then you have a bad parking brake adjustment.

    I don't think it is a bleeding problem. Air in the brake fluid only leads to brake performance degradation. It doesn't lead to stuck brakes. Unless somehow there is too much brake fluid pressure.
     
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  19. andreimontreal

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    Btw I've already tried this when bleeding. I think it loosened up the wheel, and after bleeding it stayed like that. But still sticking like I said. I dropped my folks at the train station this morning and the mpg seemed to have improved - but it was freezing (felt like 10F or worse, the car got warm very slowly), I'm not sure how much more fuel I would burn in these situations. Let's see what happens when I unhook the parking line.

    Thanks guys :). I'll wait a day or two to wait for the weather to get warmer and I'll come back with results.
     
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  20. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    My tactics:

    1. Ensure correct piston orientation at assembly.
    2. Push brake pedal multiple times, ensure everything really seated. Do not use parking brake.
    3. Reconnect 12 volt neg cable. (this should be disconnected before starting any work, to be really safe)
    4. Go for short test drive, going real easy on brakes.
    5. Upon return, apply release parking brake a few times.
    6. Raise rear of car and verify the wheels are relatively free spinning.

    Every depression of the parking brake pedal pulls on a lever which can, if the pin is not solidly bedded between the piston spokes, cause the locking pin on back of brake pad to ride up on the piston caliper spoke.

    All of the above is just one possibility, albeit my favourite, lol. The aftermarket caliper could also be the issue, and/or the brake fluid issues.
     
    #20 Mendel Leisk, Nov 18, 2019
    Last edited: Nov 18, 2019
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