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Brake Failure at HPDE, Questions?

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  • Brake Failure at HPDE, Questions?

    I rebuilt my leaking stock calipers maybe 2 weeks ago with fresh seals, did a DE today at PBIR today, everything held up great the entire day until the last open session, out of nowhere i spun in a straight line 2x braking at the straight before the chicane and 2x breaking after the front straight into turn 1 , I thought it was due to lowering tire pressures (since that was the only major change from the previous sessions).

    Got black flagged (they thought i was pulling the ebrake and drifting), Im like are you guys retarded? You think im gonna pay 300$ a day to get ejected for drifting?. I decided to call it a day since I would only have gotten another 4-6 laps in. As I drove home I noticed the pedal was significantly softer, started driving very slow and braking early on the highway. I figured maybe I boiled the fluid, since the last open session is 2x longer than any session. Made it back home safe.

    Took a nap. Woke up to check on the car. All the fluid came out of the front left and right calipers onto the concrete, master cylinder was 1/4 full (mind you, at the track day I checked the master after every session, it was full every time). The fluid was also clear/new, I think its supposed to be dark/muddy if it boiled right?

    Long story short, took the wheels off, brake lines are not leaking or broken, but its def leaking from the pistons, Im going to replace the master cylinder seals (which is replaced a few months back), and replace the seals on both the front calipers. The rears are not leaking and look 100%.

    What could have caused this?
    If the seals were bad wouldn't they have failed right at the beginning of the track day?
    Could overheating the fluid destroy the seals?
    What else should I check for?
    Scorching of the caliper cylinder wall or piston? (When I took the pistons out, I heard a lot of air and fluid burst out, So I know its got at least some sealing ability)

    This was my last track day of the year, I will not be going to another one for 2 years due to having to save up for grad school, and reducing wear and tear on the car. Its my only car.


    For reference

    1993 S13 Coupe, 165,000mi
    KA, Intake, Stock
    Koni Yellows, RSR Springs, F+R Sways, CS Tension Rods, Engine Mounts
    Dunlop Z1 SS

    Stock Calipers
    Hawk 9012 Blues
    Brand New Blank Rotors
    Valvoline Syntec Fluid

    Thanks
    Last edited by Serebros; 04-28-2012, 10:31 PM.

  • #2
    What Rebuild/Seal kit are you using? I've had bad luck with Dorman products for brake seals from them being the wrong size seals in the specified kit to them leaking just a few months after being rebuilt.

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    • #3
      Originally posted by KA240SX808 View Post
      What Rebuild/Seal kit are you using? I've had bad luck with Dorman products for brake seals from them being the wrong size seals in the specified kit to them leaking just a few months after being rebuilt.
      Dorman/autozone

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      • #4
        1. Discolored fluid is a sign of age and contamination, not heat.
        2. Dorman stuff is generally pretty low quality. I wouldn't trust it. Given the temps you run into on the track, im betting you melted the seals in the calipers and they finally gave up on the last session, causing you to have no front brake and continually lock the rears.
        Originally posted by SoSideways
        I don't care what color they are as long as they are LONG AND HARD.
        '04 G35 Sedan 6MT- The DD
        '96 240SX- The Track Toy

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        • #5
          Changed it with true torque seals from advance auto parts. If you go to advance make sure they are 54 mm seals and not the 57mm ones, there are two part numbers tied to the 240sx there , the correct part number is d352020

          Works fine now

          Thanks

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          • #6
            *advance auto parts

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            • #7
              any reason not to choose an OEM rebuild kit? in a time bind for availability? i've had good luck with the oem stuff on the z calipers.

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              • #8
                Originally posted by gawdzilla View Post
                any reason not to choose an OEM rebuild kit? in a time bind for availability? i've had good luck with the oem stuff on the z calipers.
                honestly i dident realize something as simple as a brake caliper seal could have quality differences between companies, to me its like a 10amp fuse, should be pretty much the same as any 10amp fuse anywhere on the planet

                and i was in a bind, had work the next morning, and i called everyplace pepboys, napa, orielly, autozone, advance was the only one who had it in stock without ordering

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                • #9
                  I'm glad you and the car are OK. Brake failures on a road course are scary. If that happened at the wrong spot and you were really pushing it, something really bad could have happened.
                  Chicago Region SCCA SM # 688 http://www.scca-chicago.com
                  TSSCC SM # 688 http://www.tsscc.org

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