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Help! Front Brake Sticking While Driving.

Discussion in 'Gen 2 Prius Technical Discussion' started by GreenPriusGuy, Jun 11, 2018.

  1. GreenPriusGuy

    GreenPriusGuy Junior Member

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    Hello all!

    First: I'm new to the forum, so I hope this is the right place.

    I picked up a 2006 Prius for the low a couple months ago. It had a bad wheel bearing and axle. I replaced the wheel bearing and both axles, then the front passenger brake stuck and was smoking after the first test drive. I don't think it was stuck before. I compressed the caliper like I would any other car when I went to put it back on, just as I did on the driver side without issue.

    Anyway, as far as diagnosing why it's sticking I am confused.

    I took that wheel off today and turned the car on and pumped up the brakes. I then opened the bleeder and no fluid shot out which leads me to believe pressure isn't being kept in the system (bad brake line or something). Also, I was able to turn the wheel by hand. It was not stuck on, but it burns when I drive! The caliper also compressed super easy when I went to put it back on after changing the axle. The slides in the mount don't seem to be frozen either. I haven't taken it apart to check, but I can wiggle the caliper around.

    There are several lights on the dash, but no codes found with my Autel code reader. The lights are the (!) (tire pressure last I checked), ABS, VSC, and BRAKE.

    What should I do?

    If you need any more info or want me to take something apart for a looksie let me know.

    Thank you!
     
    #1 GreenPriusGuy, Jun 11, 2018
  2. harryarcos

    harryarcos Junior Member

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    Might be worth looking at the posts following my question dated Feb 18 2017: 'Front brakes stuck after fitting new pads'. Many are about the 'Phenol' pistons which tend to swell, although mine also had a manufacturing fault with the caliper. The whole braking system is rather complicated and cannot be bled in the traditional way. A fair bit of 'homework' is required before attempting work on the system. Best of luck.
     
    #2 harryarcos, Jun 11, 2018
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  3. Robbski

    Robbski Junior Member

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    Are the slide pins moving freely?

    BTW - After I did the brakes (including new rear wheel cylinders) on my newly acquired high mileage 05 I took it to the dealer to get the system bled. I hate to pay people to work on my cars but my research into Prius brakes made my nervous enough to decide it was a job that I didn't have the expertise or equipment to do properly.
     
    #3 Robbski, Jun 13, 2018
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  4. GreenPriusGuy

    GreenPriusGuy Junior Member

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    I took it to a dealer for the same reason. If they mess something up, then it's their fault.

    Apparently the front driver side caliper is bad and the passenger caliper isn't sticking. I'm not sure what's causing it to get so hot. The dealer found a code for the driver side caliper that my scanner didn't pick up for whatever reason.

    If they replace the caliper and everything is good afterwards, then whatever. Cool. Great.
     
    #4 GreenPriusGuy, Jun 18, 2018
  5. GreenPriusGuy

    GreenPriusGuy Junior Member

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    Update for anyone that finds this thread:

    The dealer found metal shavings on the driver side wheel speed sensor. Apparently that can cause false codes. I guess the shavings came from the demolished bearing that was on that side. They cleaned the sensor and popped it back in. The lights are gone and the car seems to drive normally, but I've only driven it a few miles since.
     
    #5 GreenPriusGuy, Jun 23, 2018
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  6. bisco

    bisco cookie crumbler

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    congrats, all the best!(y)
     
    #6 bisco, Jun 25, 2018
  7. ericbecky

    ericbecky Hybrid Battery Hero

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    Thanks for taking the time to follow up with the solution to your problem. It will hopefully help others in the future.
     
    #7 ericbecky, Jun 25, 2018
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  8. ChapmanF

    ChapmanF Senior Member

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    Hummm....

    I can certainly believe speed-sensor related codes being set because of metal shavings on the speed sensor. (Those wouldn't, of course, technically be "false" codes.)

    Not sure I'm prepared to buy that metal shavings on the speed sensor were causing the brake to physically drag and smoke. That's more than some codes, right there. Is the dragging all cleared up now too?

    -Chap
     
    #8 ChapmanF, Jun 25, 2018
  9. ITBland

    ITBland Active Member

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    The job of VSC is to keep all wheels turning at the same speed if the steering wheel is pointing straight ahead. If one of the sensors is giving a bad reading (too "slow" because it is partially blocked by metal shavings causing it to miss signals from the "tone ring") the response would be to activate the brake on the opposite side to slow it to the same speed as the "slow" wheel. Eventually, it throws a code because it cannot correct and needs to tell you it has given up, and you no longer have VSC working at all. ABS does the same thing, only when braking.
     
    #9 ITBland, Jun 25, 2018
  10. ChapmanF

    ChapmanF Senior Member

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    While I admire the truthy sound of this proposed explanation, it's not yet one that I'd bet a sandwich on unless you have, or know of someone who has, actually confirmed with instrumentation and datalogging that it's genuinely happening, in this instance or some other. Otherwise, a bit too much of a succotash of 30,000-foot generalizations of what we all know about VSC and ABS stirred in with everything we don't know about unpublished algorithm internals and stuff we haven't measured or tried to confirm.

    I guess an experiment might be possible....

    -Chap
     
    #10 ChapmanF, Jun 26, 2018
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