Brake failure!

I've been out, tracking the last two weekends in my new (to me) '99 996.1. Having a blast - mostly. Brake failure several times in the last 4 days at two different tracks. It happens when they're pretty warm, but not boiling - and comes on quick! Several times, I've noticed just a bit of fade for a few corners - then 'to the floor'. I can pump and get enough to slow - but it's pretty hairy at speed! No sign of boil over. But I bleed the brakes, and top up with good Dot4 fluid - and during that time, they cool, and they're fine - for a while. What does this sound like? Master cylinder?? Wheel bearings?? Any ideas??

Sounds like you have air trapped in the line. Im sure you will have allot of responses. My opinion bleed out again after 24hrs of cool down, starting furthest from the MC, I would bleed the old fashion way so you will need a second man. Didn't say what fluid you are using but I would switch up to a track level brand; even consider a full fluid flush.

What type of pads are you running?

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It sounds like fluid boil fade. Do a thorough flush with a high boil point DOT 4. Pick one here based on dry boiling point vs price per ounce. https://www.lelandwest.com/brake-flu...ison-chart.cfm I get by with regular old Ate 200 but I flush twice per year.

Couple questions..... How do you bleed your brakes? How much to you take out of the system when doing a bleed? What type of pads? Braking to much? Deep into the corners? Do you ride the brakes going thru corners? What fluid do you use? Have you checked the piston seals on your calipers? Lots of questions......

We bleed the old fashioned way and do 3-4 pulls at each valve (in the correct order). Run Endless dot 4 fluid and Pagid yellows in front and black in back. I try not to abuse brakes and stay out of anti-dive. I've driven a good number of cars that didn't have this problem. And one of the tracks was big Willow Springs, which is really easy on brakes, and it happened after 6 or so laps. Excessive heat shouldn't have been an issue. It's vexing.

Are you noticing any caliper getting discolored? My left front got nasty. I rebuilt my calipers and on 1999 car all the seals were shot.

How long have you had your brake fluid in there and when was the last time you did a complete flush? Some high performance brake fluid tend to collect moisture more easily than traditional so it must be flushed regularly to remain effective. Also a pressure bleeder like Motive can do wonders to ensure you have no air in the lines.

the best racing brake fluid that money can buy and maybe brake cooling ducts if the fluid does not cure it. check for glazed pads and rotors

With the information you provided, you could have a leaking seal on the master cylinder also.

As others have said, it sure sounds like you have some water in the lines, and it's flashing to steam when the brakes get hot enough. Getting rid of the moisture and the GT3 ducts to keep the brakes cooler is a start...

Not nice when the pedal goes to the floor. Had it happen many times until I got serious. Happens fast when it happens. Castrol React SRF, IMHO, and you will never have this happen again. GT3 scoops. I'm running slicks and am at the limit of the stock brakes, and I can still keep a somewhat hard pedal.

This is a crosspost from OT - and an AMAZING example of saving the car when the brake pedal hits the floor: GT500 almost CRASH at Hockenheimring - File404.net - YouTube Warning: Language (and maybe bodily function sounds)

I have actually yelled that to myself several times during DE's......helps me think

Amazing video, 5CHN3LL! Pretty hairy feeling!! We've run a ton of racing fluid through the system in the last two weeks. And I put on GT3 ducts after the first failure. The more I think on it, I think Paul's right. I'm thinking master cylinder...

Is it worse if you hit curbing or bumps? And/or after only left or right turns? You might have a rear wheel bearing going... and you're getting pad kickback. You said you're using the Pagid Yellows, can you confirm they're the RS29 compound? Those should be able to withstand the heat. 2 more questions for you: What kinds of tires are you running? Or course R-compounds will have more grip and cause the braking system to absorb extra energy (heat). And, what are the other car(s) you track? Could this be compounded by a lack of appropriate technique?