As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI OUT DURING BRAKE CHECK CAPTAINS LEFT BRAKE WENT ALL THE WAY TO THE FLOOR. UPON ACTIVATION OF THE CO-PILOTS LEFT BRAKE, BOTH BECAME SPONGY. RESET BRAKE SHUTTLE VALVES, BLED BRAKE SYSTEM. PERFORMED SEVERAL BRAKE CHECKS STILL AND WHILE TAXIING WITH POWER BRAKE SELECTED ON AND OFF. NEVER GOT BRAKES TO FAIL. SOLID BRAKE PEDALS AT ALL TIMES IAW MODEL 560 MM 32-42-00.