Gary R.

I've been DE'ng and racing a 911 for 10 years, never an issue with the hi-temp fluid I use boiling but it appears that's just what happened yesterday while the wife was driving at Limerock. Brakes were fine for one application, then pedal just mushed to the floor the next. She came in and I sat in the car with it off, pumped a couple times and pedal was rock hard. Started the car back up and the pedal just slowly went to the floor with constant pressure. After about 15 minutes all seemed fine again. Drove home, drove today, all is well. I'm wondering if PSM was intervening a lot and that caused it? It was fine all day with both of us driving, about 6 25 minute sessions.. Is there something else I should be looking at? I'm going to flush this fluid and go up a step to Castrol SRF but I have been using Performance Friction fluid for quite a while without issue..

Verboden

How long ago was the last fluid flush?

Gary R.

3 weeks... it's fresh

Verboden

The symptoms certainly point to the fluid, especially since everything is working after cooldown. Since it was recently flushed, any chance the fluid came from an already open container - contaminated?

You mention PSM, that could contribute. If you have the chrono the more aggressive settings are supposed to back off on its intervention - meaning either without chrono or it set on normal you would get more intervention.

Since your wife was driving, any chance she was trying more aggressive braking or trying experimenting with lines that in turn might have triggered PSM.

Look at the pad thickness. Many have mentioned that when the thickness gets thin they will transfer more heat to the caliper piston. Also look at the inner pads, maybe there is a sticky piston or dragging pad.

Sorry, that's all I got. Good that everyone plus car came home safe.

the_vetman

Was the brake pedal getting soft and going down far, or was it literally down to the floor with no brake pressure whatsoever? I ask because soft brake pedal especially on the track is notorious in 987s. GT3 master cylinder is the fix if you're getting a soft pedal that's going far down on the track.

Gary R.

Fluid fresh Performance Friction, Pads at 75%+, running in Sport+ but I left PSM on for her. Pedal was mush, not 0 resistance but continued firm pressure resulted in the pedal continuing to move down with little actual braking occurring. Why would the GT3 MC change the situation, is the standard MC bypassing hot(er) fluid somehow? I'm going to toss this in the Racing and DE forum also to see if any of the big builders have any thoughts.
Thanks!

the_vetman

No, GT3 MC just has a larger bore and moves more fluid. It doesn't change the braking capability but improves the pedal feel. HTH.

BE455

The pedal going down slowly with the engine on is normal behavior, and the fact that it stayed firm (after a few pumps) with the engine off is a sign all is well with the system as a whole.
Your symptoms are classic for boiled fluid. Many contributing factors, all noted above... car doing double duty with back to back sessions, PASM intervening, etc. Have driven Lime Rock a bunch - not notoriously hard on brakes, so from that standpoint it's a bit unusual to have the symptom here and not elsewhere.

Regardless, the issue is what to do about heat. Adding cooling ducts can help... GT3 air ducts are cheap and easy for the front. 997TT rear ducts fit with a fair amount of trimming. Can search around here or P9 for images. For me, that wasn't enough - still boiling regularly, so I jumped up to larger calipers (996 gt3 6 piston) in front and bigger rotors front and rear. Unfortunately, this is just a weak point for the 987. The GT3MC does improve peddle feel, but won't help if your issue is boiling... just gives a nice / confidence insipiring peddle feel when the system is air-free.

Bill Lehman

The best improvement for me was adding Olsen Motorsports front ducts. They took a fair amount of fitting but do seem to work. I am also running GT3 front ducts and modded TT rear ducts. Best fix for rear is to leave PSM off, Sport button on. PSM will definitely intrude on an otherwise good line through a corner, car practically quits in the toe of the boot @ WGI.

bernb6

Overheated calipers may have changed color - check the front vs rear for color change. If the rear, then PSM is almost certainly the culprit. If the front, then your wife may be significantly over braking so, even though the course may not be hard on brakes, she might be.

Mussl Kar

Good thing Porsche seats have "anti butt pucker" leather on their seats. Your seats will recover. Your pucker may not be so quick to recover.
I swear my RS sometimes goes into Ice Mode sometimes, another subject.

TrackDays247.com

PFC fluid 665 is great stuff....I suspect the REARS...yes, the rears...they may have boiled. Such a trouble prone area, small calipers/relatively small rotors, have seen lots-o-trouble out back on these cars, and PSM really activates the backs way more than you'd think! Hope this helps a bit -

Gary R.

Yep, i'm going try turning PSM off for her along with a new GT3 MC and Castrol SRF fluid. May add a couple brake ducts also to get some air back there. Thanks All..

DaveCarrera4

^ This. Did any of the calipers turn to a more "rusty" red color?

Gary R.

Nope, everything looked and smelled perfectly normal, if anything the fluid (when I checked the level) seemed a tad higher viscosity but that my just have been my perception at the time..