2005 - Sterring Knuckle Caliper Bracket Bolt Holes are threaded - Heli-Coil repair?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Seth4, Oct 21, 2021.

  1. Seth4

    Seth4 Junior Member

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    Does anyone have any experience repairing their Steering Knuckle Caliper Retention Bolt Holes' after they've become threaded? Specifically on a 2005 Gen 2? I was replacing my Calipers' and I got their Retention Bolts' out from the Steering Knuckle... but could not get them back in. It was extremely difficult to crack the top Bolt and I am assuming there was Rust welding and that the Threads were destroyed when I removed it?

    [​IMG]
    Here is the Driver Side Steering Knuckle. The Bolt Holes' in question are the two Caliper Retention Holes' on the left side of the Frame; near the middle, and the bottom left. These Holes both appear to be threaded on my Steering Knuckle and the Original 17mm Retention Bolts will no longer catch a thread.


    I have found that people commonly repair this issue using a product called "Heli-Coil". It creates a replacement (but reliable?) thread. Does anyone here have any experience using this or a similar product to "re-thread" a Caliper Bolt Hole in the Steering Knuckle? Thoughts? I understand that the most optimal solution is to replace the Steering Knuckle entirely but I am assessing the options. If you are familiar with this process, specifically with the 2005 Gen 2... what size Heli-Coil Kit should be used? I have found that most people seem to use "Heli Coil Kit - M9x1.25" but I don't know if this Size is correct for this Model of Car or how to precisely figure that out.

    Any help is extremely appreciated, thank you.

     
  2. Georgina Rudkus

    Georgina Rudkus Senior Member

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    There are no M9x1.25 bolts on any Toyota vehicle.


    If the bolt has a 14mm hex head, the bolt is M10x1.25.
    Toyota uses J.I.S. or Japan Industrial System fasteners.
     
  3. ChapmanF

    ChapmanF Senior Member

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    Heli-Coils and Time-Serts work well. I'm more familiar with Heli-Coils, Time-Serts might be newer (but regarded as sturdier). Nothing I've repaired with a Heli-Coil gave me a problem.

    On the other hand, the caliper mounting to the knuckle handles substantial forces, and there's not a whole lot of meat around those holes, and some of it goes away when you bore oversize to put the insert in, and the knuckle only sets you back a shade over $200 even if you get one in a red and white Toyota box.
     
  4. Georgina Rudkus

    Georgina Rudkus Senior Member

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    You'll be just fine with the HeliCoil. The weakest link in a fastener is always the bolt, which is under tension when tightened,

    Failure always occurs with the shearing, by either ductile or brittle fracture of the bolt, not the threaded hole or the nut. Ductile fracture occurs with low tensile bolts, while brittle fracture occurs with hardened bolts.

    Failure of the internal threads only occur from corrosion ir mechanical upset, such as cross threading.

    A larger diameter threaded hole is much stronger than the original.

    HeliCoils are approved for mission critical fasteners in aircraft. They are often preinstalled in soft and weaker frangible materials like plastics and aluminum to achieve greater impact resistance in harsh environments.

    You'd be just fine, if you use a HeliCoil.
     
  5. Seth4

    Seth4 Junior Member

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    Thank you all very much.

    It is a 17mm.

    I found this Reference Sheet for Heli-Coil but I am still not sure what size Kit is called for. https://www.mutualscrew.com/media/refguides/helicoil%20chart.pdf

    With a 17mm Bolt ~11/16 in, does anyone know what Size re-threading Kit should be used?
     
  6. koco

    koco Member

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    Is it possible to use a longer bolt and put a nut on the other side?
     
  7. Seth4

    Seth4 Junior Member

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    I've seen people talk about this working but the Bolt is currently just loose inside the Hole, there is a gap because the Threads are gone. I am thinking of using a rethreading Kit and trying to put a Nut on the other side.
     
  8. Georgina Rudkus

    Georgina Rudkus Senior Member

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    Both 14 and 17 mm hex heads are used on Toyota M10x1.25 bolts. To verify which you need, just measure the width in millimetres across the tip of the bolt. Toyota only uses 1.25 thread pitch bolts.
     
  9. koco

    koco Member

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    17mm is the size of wrench you would use on the bolt, but the diameter of the bolt itself is not 17mm.
     
  10. Seth4

    Seth4 Junior Member

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    I see, my bad. So I need to measure the flat end of the Bolt? The end that I do not use the wrench on?
     
  11. Georgina Rudkus

    Georgina Rudkus Senior Member

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    If you don't have a metric ruler just fit a 10 mm open end wrench over the tip to check the width,
     
  12. Seth4

    Seth4 Junior Member

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    Thank you, and just to be sure I need to be measuring the width of the Section with the Threads? Not the "Head"?
     
  13. Georgina Rudkus

    Georgina Rudkus Senior Member

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    Correct
     
  14. koco

    koco Member

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    It might be an M12 bolt, so 12mm diameter. And if you do decide to get a longer bolt and use a nut make sure the new bolt is the same grade as the old one so it doesn't break.
     
  15. Georgina Rudkus

    Georgina Rudkus Senior Member

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    It's a special necked down collar bolt. If you a longer want one, it would have to be custom made.
     
  16. koco

    koco Member

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    This is true about the specialty bolt...using a different type could have negative effects on braking. I think they are called shoulder bolts with a flange, or flange bolts with a shoulder. Maybe just go to a junkyard and buy a used spindle part for a few bucks.
     
  17. mr_guy_mann

    mr_guy_mann Senior Member

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    Ummmm. You DO realize that according to the service manual, the bolts that hold the front brake caliper mounting brackets go THROUGH holes in the steering knuckle and into threads in the bracket itself? (torqued to 81 lbs-ft) Screenshot_20211022-223752_1.jpeg

    That said, I wouldn't be surprised if you had a bunch of corrosion built up IN the steering knuckle holes (around the bolt shanks).

    Posted via the PriusChat mobile app.
     
    #17 mr_guy_mann, Oct 22, 2021
    Last edited: Oct 22, 2021
  18. mr_guy_mann

    mr_guy_mann Senior Member

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  19. SergeyS

    SergeyS New Member

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    Why you don’t consider to buy a used part from junk yard? It’s only like 50$
    Don’t play or experiment with a brakes.
     
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  20. Seth4

    Seth4 Junior Member

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    No I did not realize that, thank you. I am concerned that the bolt is loose inside the Steering Knuckle hole, is this an issue? There is a maybe...1mm gap around the Shank.


    I am not opposed to that, just exploring the possibles.
     
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