dsrufer

Rennlisters:


I could use a moment of your guidance with respect to a brake pedal going down to the floorboard. Here is what I know:

1. Stock 2011 Cayman S (987.2)
2. Track event decelerating from 100-ish MPH
3. Brakes were warmed up (20 minute mark of aggressive driving)
4. Brake pedal went to the floorboard slowly (about 3 seconds)
5. Car slowed down but only slowly (like applying half the brake pressure)

Once in the paddock, the following was determined:

1. Brake fluid had come out the reservoir (a decent amount)
2. Zero air when bleeding the lines
3. Good rotors
4. One-third remaining on track brake pads

After the bleeding, the brakes seemed okay but were not tested at full speed or temperature.

Thank you for your input and guidance. All is greatly appreciated.

Dan

phroenips

What kind of brake fluid was in there previously, and how old was it?

ekam

Did you check and make sure there's no leaks in the lines and thee seals in the calipers are in good shape?

dsrufer

Thanks for the responses. I'll add:

1. Reasonably new stainless-steel brake lines
2. Zero brake line leakage (not a drop anywhere along the lines or at the calipers/pistons)
3. New racing brake fluid (600 F+)

Honest.

Thanks again.

Dan

MrMoose

Sure sounds to me like you boiled the fluid. You want fresh fluid for the track, and make sure it's DOT 4.

(Posted at the same time as you. If it was fresh racing fluid then no idea.)

phroenips

That was my first thought as well. I mean, I suppose it's possible the brake fluid was still boiled despite being high temp/racing fluid? I know I've had that happen on my Audi RS5, but that's a 4000 pound pig.

gman3280

ClassJ

MyNameIdeasWereT

Just because it's high temp fluid, doesn't make it immune to overheating. It's significantly less likely, but it's entirely dependent upon your braking habits on track.

Did you check brake fluid level before the event? How much brake fluid did you lose? That would be my greater concern, a significant loss means that it's going somewhere.
But also keep in mind that when pads get significantly worn down, it takes more fluid to fill the caliper pistons, so the reservoir may read lower than expected.

Pep!RRRR

986

As pads are worn down they are more prone overheat the caliper and boil the fluid also.

What pad brand / compound are you using? Also do you have GT3 brake cooling ducts (they cost less than $10 and take 5 minutes to install.)

dsrufer

Thank you each for your responses. All is greatly appreciated. GMAN-3280's feedback is in line with the race track consensus pointing to an issue with the master cylinder. Since we know the brake lines were okay (no leakage, no air, etc.), the displacement of brake fluid in the reservoir must have occurred at the cylinder (via a piston issue?). It's headed to the shop.

Thank you again.

Dan

MrMoose

I could be wrong, but I don't see how the MC could fail in a way to cause fluid to be pushed out the reservoir. My thinking is still that the fluid in the lines boiled, which pushed fluid out the MC. You wouldn't find air in the lines when that happened as when things cooled down the fluid in the lines would just re-condense (there's no way for air to get in there unless the MC was completely drained.)

Anyway, see what the shop says.

daylorb

Sure sounds like the fluid boiled/came out - what else could it actually be? Sounds like a good call to take it in and have it checked-out.

Turbodan

if fluid came out around master cylinder it sounds like that is your problem.