Hey guys,
I was doing figure eights at the track paddock to get a feel for the cars limits. After I completed 3 figure eights, my brakes felt mushy, even though I used my brakes very little (although I slid (primarily understeer) throughout the event), at the end of the event. However, after that initial press almost to the floor, the brake reacted almost normally again (meaning the pedal feel was intermittant in terms of how far the pedal traveled before it stopped). However, I was always able to stop well, just with more travel.

On the way home, after about 40 mi. of freeway driving, my brakes were completely back to normal.

Now I know that over-heating the brakes, boiling the brake fluid, and air/moisture in the brake fluid can cause the above. Any others?

I have ruled-out brake fluid boil because I have ATE Blue DOT3/4 synthetic fluid.

As for over-heating, I have the track model which comes with the brembo's, so over-heating and brake fade would be unlikely.

This leads me to believe since I had my brake fluid recently replaced, that it could be air in the system. Does this sound reasonable? My only question is why after doing the figure eights where I used virtually no brakes although I was sliding all the time. Also please note that VDC was off.

Thanks in advance for all the replys and help!

 

My only suggestion is to bleed your brakes again. With an ABS system, I would recommend it be vacuum bleed instead of the standard method. Most ABS systems have to be vacuum bled to insure all the air is bled out.

 

I would not worry about using a "mighty-vac", I would just bleed them liberally. Vaccum is great for convenience, but regular bleeding is fine. I use one, but only so I don't bug the crap out of my wife to come pump the brakes. Put it this way, they only advise regular pump bleeding in the factory service manual.

 

I did not see any special precautions for bleeding the old DOT 3 out of the ABS. My local dealership did not have any advice either. Just to be ****, I replaced my fluid (after changing lines and pads) with Motul 600, test drove it for an hour, slammed on the breaks 2-3 times engaging the ABS and then blead them some more. I did not see any difference in the fluid after, and did not have any more air in the lines.