Rear brakes seized after stainless line install - BOSS 302

Discussion in 'S197 Technical Forum - GT, Boss 302 and GT500' started by Spencer Terry, Feb 13, 2019.

  1. Spencer Terry

    Spencer Terry TMO Intermediate

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    Hey Everyone,

    I installed some russell braided lines this week and the rear calipers were immediately stuck with the piston pressing against the rear rotors. I swapped out rear calipers and it locked up the next set as well. This stainless line set was supposed to be for GT Brembo equipped cars per the reviews and Q&A Section on these brake lines. Assuming our cars brake system is essentially that of a Brembo GT, I installed them...

    It seems so odd that the fronts work as they should but the rears are instantly applying full pressure. I had a mechanic handle the second round of calipers to be certain I wasn't somehow screwing up the brake job.

    https://www.americanmuscle.com/russell-brake-kit-0514-abs.html

    So, that being said, is there something specific to a BOSS 302 car that would cause this to happen? Perhaps something in the ABS system? Seems odd it would only affect the rear brakes!

    Thanks in advance
     
  2. Coz

    Coz TMO Race

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    Did you (or the mechanic) make sure that the slots on the caliper piston were lined up vertically to match up with the pins on the pads? If not, the extra width caused by a mismatch could result in the pads always rubbing.
     
  3. TMSBOSS

    TMSBOSS TMO Addict

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    I has seen this happen on a 2013 Boss. Reinstall properly and problem solved.
     
  4. Spencer Terry

    Spencer Terry TMO Intermediate

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    We left the braided lines on and put the new rear calipers on with the piston pushed back until it bottomed out. This guy races AI cars, has always been on the s197 platform and knows it well...

    That was my initial thoughts well however, but I don't understand why i functioned properly once we put the stock lines back on.
     
  5. Spencer Terry

    Spencer Terry TMO Intermediate

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    Do you know what was installed incorrectly the first go round?
     
  6. JAJ

    JAJ TMO Addict

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    I wonder if the problem is that the banjo bolts are too long and they're interfering with something inside the caliper. Is the banjo ring thinner on the Russell parts than on the stock ones?
     
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  7. TMSBOSS

    TMSBOSS TMO Addict

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    The two dimples on the back of the pads were not properly seated in the slot on the caliper piston. I turned the piston back in and lined up the pieces. Problem solved.
     
  8. Spencer Terry

    Spencer Terry TMO Intermediate

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    I re used the stock bolts, the kit didn't come with any hardware (I think that may be why it is slightly cheaper than others).
     
  9. Coz

    Coz TMO Race

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    If the brake fluid flowed properly when bleeding the brakes, I can't see any issue with the lines or banjo bolt.

    When you reinstalled the stock lines and recompressed the piston, maybe the slots in the piston coincidentally lined up properly with the dimples on the pads.
     
  10. Spencer Terry

    Spencer Terry TMO Intermediate

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    We did bleed them and they flowed properly, I can only imagine somehow they are not being allowed to back off the piston once they are back on...

    We did confirm the little dimples lined up from the back of the pads with the piston... We are going to try them on a buddies 2013 brembo car
     
  11. JAJ

    JAJ TMO Addict

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    Going back to my earlier post, and noting that it's been years since I installed braided lines on the back of an S197, I still think that you should take a close look at the way the banjo bolt goes into the caliper. If you have a loose caliper, look in through the fluid port and see what's behind it. From the picture on the AM website, it looks like the banjo bolt goes in at right angles to the piston - if it screws in too far, can it stop the piston from retracting?

    If I'm reading this correctly, you had this problem with two different sets of calipers, correct? It has to be an installation problem - the hoses and pistons are dead simple setups that always work, so there's something not right with the mechanics.
     
  12. TMSBOSS

    TMSBOSS TMO Addict

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    Are you running the larger GT-500 rotors? If so, you may have to clearance the caliper brackets for they clear the rotors.
     
  13. blacksheep-1

    blacksheep-1 TMO Addict

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    I'm thinking, if the little dimples are lined up, and the pucks are fully retracted, it is the banjo bolt, many banjos are smaller than the ones they replace, or have recessed copper washers, which in effect, makes them narrower
     
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  14. Coz

    Coz TMO Race

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    He said he reused the stock bolts since the new lines did not come with hardware.
     
  15. VoodooBoss

    VoodooBoss Rick Moderator

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    Right but if the connector the banjo bolt goes through is thinner...
     
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  16. JAJ

    JAJ TMO Addict

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    Maybe I haven't explained my question about the bolts clearly enough, so I'll give it another go.

    The banjo connector is made up of a ring with a hose fitting on the side (called the "banjo" because it's shaped like one) and a hollow bolt that goes through the hole in the ring (the "banjo bolt"). When you install the fitting, you put a copper sealing ring on the banjo bolt, put the bolt through the hole in the banjo ring, add a second copper sealing ring and screw it into the caliper and tighten the whole assembly down. If the Russell banjo ring and the new copper sealing rings are thinner from face-to-face than the OEM Ford ring and seals, then the OEM Ford bolt will screw further into the caliper than it would with the OEM fittings and rings. Simply "using the stock bolts" doesn't mean it will fit.

    My question was whether the Russell banjo assembly is thinner than OEM and whether they've checked to see if the banjo bolt is actually screwing far enough into the caliper that it's binding the caliper piston and stopping it from retracting.
     
    Last edited: Feb 14, 2019
  17. Spencer Terry

    Spencer Terry TMO Intermediate

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    This is certainly a possibility, and yes two different calipers seized up... I did run it with the stock rear lines and stainless up front at CMP this weekend and she never failed me (Thankfully). I was checking lines in between every session!

    I am going to look at the banjo bolt when we install this on the Brembo car.

    Thanks for all the help!
     
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  18. Spencer Terry

    Spencer Terry TMO Intermediate

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    I am not running GT500 rotors (yet). On the list though.
     
  19. captdistraction

    captdistraction I am the breaker of things

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    Another vote for the banjo bolt seizing the piston. I ran into this with russell and other branded lines. I can't remember the spec for the replacement bolts, but I used something 1/4" shorter and it fixed all the issues.
     
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