Green gold leak

[PeterBergin at aol.com]

Hi guys, my Audi was parked for about 5 weeks when I pulled one of my old  
toy cars out to play with after 3 years.  Put the play car back in storage  
and drove the Audi home, no problems.  The next day I started it up and  
backed out of my drive way.  I hit the brakes, were rock hard, no power  
assist, no red brake dash light or other idiot lights.  Drove about 100  feet, hit 
the brakes a few time, no power assist, pedal travel normal.
 
Turned off key and pumped the brakes a few times, normal travel.   Started 
car and had power brakes, returned to drive way and found a puddle  of green 
gold.  I think it cam out the overflow cap on the resiviour. The  level was 
down about an inch.
 
I have not touched the car since.  Any sugestions?   (bomb was replace at 
75k by previous owner, I have not  touched it.  Have never has any prior 
issue like this.  Have  rebuilt the pump twice and replace the rack and hoses.  
No prior  leeks, never have to add the green gold. 238k on the clock.
 
Thanks, Pete