[FIAChamp]

Hey guys,

Recently took my 2006 DC5 running Wilwood Dynalite BBK to Streets of Willow. After one session, the brake pedal got incredibly soft. I drove the 2nd session much more cautiously. It felt as if I could get similar braking power but it took much more pedal travel before brakes began to bite. And my pedal was going to the floor whenever I had to threshold brake.

Key configuration info:
Running Motul RBF660 fluid, replaced days before trackday
Running Wilwood BP-20 pads, replaced and bedded same time as fluid change
Didn't have time to resurface or buy new rotors before trackday / new pads
Pedal travel to initial bite went from almost instant before trackday to no bite until pedal about 1" in after 2 sessions

After last session, noticed some moisture around two bleeder nuts.

Any hypotheses on what's wrong and how to check?
I bought some Endless fluid and new rotors but fear I may have to replace brake master cylinder :-/

 

[Hyoriu]

did you try bleeding your brake system again first? same results?

 

[Dad]

Maybe the bleeder nuts have failed? You could try replacing those as well but the BMC had an open recall years ago that I had to take my car in to get replaced. Produced similar symptoms to what you are describing

 

[TheRickster]

Where there is smoke there is fire, I'd look at the bleeders first and go from there.

You could have also somehow cooked the fluid if there was a sticking caliper etc.

 

[Sonicc]

It takes quite a bit to boil Motul RBF660...

so i think one of the two things happened:
1. you didn't fully bleed the brakes first time and there's moisture/air in the lines
2. bad brake master cylinder

 

[TheRickster]

It takes quite a bit to boil Motul RBF660...

so i think one of the two things happened:
1. you didn't fully bleed the brakes first time and there's moisture/air in the lines
2. bad brake master cylinder

Yeah hence the sticking caliper. Could also have contaminated fluid like you mentioned.