Boiling fluid

[larry leung]

>Anyways, after my runs I'd pop the hood and I noticed
>that my brake fluid tank had spillage around the cap,
>even tho the cap was tight.  I geuss the fluid boiled
>over in the tank and vented thru the cap somehow? 
>Brakes still fine fine, they never faded.  I'm going
>to flush the fluid anyways as I'm installing a set of
>SS brake lines, but I thought that was kinda wierd...


Being an experienced autocrosser (15yrs, 3 regional championships, yadda, yadda), I really haven't seen any brake fluid boiling at an autocross, even at Divisionals which have higher speed (street cars get solidly into the 50+ MPH range, which doesn't sound fast until you try it, mods get upwards of 75+ MPH, really a blast without the expense of road courses)longer duration (usually around 110 to 120 second courses). The most I have seen is occasional brake pad fade from overzealous left foot braking. 

If you really boiled the fluid (a sign of way too much water absorbed by the fluid, which means it's really, really WAY too old!), you'd note a sinking brake pedal which would go away after the fluid cooled, which you didn't mention. 

My guess is that you had the brake fluid reservoir overfilled, so that the normal heat expansion of the brake fluid forced it out the vent hole. Stick to the factory recommended brake fluid level, which generally is at the seam of the brake fluid reserviors in VAG products. 

LL - NY