You guys are going overboard with the laziness of having to do a BF flush before a DE or track use. I think a fresh reservoir of BF should last 3 months of track use before needing another flush.

Race cars have brakes rotors getting hot enough to glow cherry red (at least 800 deg briefly during brake application. There is some insulation of the heat from the rotors to the brake calipers (ceramic backing plates, etc, and of course PCCB) so we're probably talking about 400+deg which is the wet boiling point of the fluid. The internal pressure under braking may be higher than atmospheric bp but the heating of the fluid is occuring during use of the brakes when brake pedals are released.

A simple solution to not changing BF as often is to use silicone oil (non-hygroscopic) DOT5 fluid. However the other fluid (DOT3 or 4) must be entirely removed by washing the lines and calipers chambers with isopropanol then acetone and blown dry before switching to silicone oil. Care must also be taken not to shake and dissolve air into the silicone oil as this is difficult to remove (except under vacuum).

As to having a closed loop system (I assume the separate ABS fluid chamber is sealed and separate), the easy solution is to hook up the vent nozzle to a lightly pressured tank of nitrogen gas (lecture bottle) at say 15 psi. That should last until you need to change pads unless you can do so without opening the brake reservoir to top up fluid as the pads wear down.

"A simple solution to not changing BF as often is to use silicone oil (non-hygroscopic) DOT5 fluid."

Silicon brake fluid, while non-hygroscopic, is not usually not recommended because of its affinity for air bubbles.

Sherwood

Sherwood,

i don't think that is true about affinity for air bubbles. I think the conversion was done improperly without the requisite isopropanol and acetone flush followed by thorough drying of the entire system to remove all traces of old glycol based BF and moisture before filling and bleeding the entire system with silicone oil. The only possible problem is the rubber seals swelling from contact with silicone oil which are in the lines and master cylinder. The reason for the flush is silicone oil and glycol based BF are not miscible and the old fluid with its contaimanants (water) will boil and make for spongy pedal.

"i don't think that is true about affinity for air bubbles."

Tshih,
I think I subconsciously mimiced Bruce Anderson's take on silicon BF.

I'll let him explain his POV:
http://www.911handbook.com/articles/pw_siliconebrakefluid.html

Sherwood
http://members.rennlist.org/911pcars

911pcars,

Great links and interesting read.

Tom