As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BRAKE FAILURE ON TAXI OUT. BRAKE ACCUMULATOR IS OUT OF GREEN ARC WITH BATTERY ON. NO VISUAL LEAKS, FOUND ANTI-SKID POWER PACK MOTOR SPINS BUT NO PRESSURE BUILD UP, PUMP SHAFT SHEARED. REMOVED AND REPAIRED POWER PACK ASSEMBLY IAW 560 MM 32-42-00. ALL OPS AND LEAK CHECKS GOOD AFTER BRAKE BLEEDING AT VNY.