As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN APPLYING PARKING BRAKE, PRESSURE DROPS FROM 3000 TO 1000 ON APPROX 50 SEC, T/S IN PROGRESS WITH SHUTTLE VALVE AND BREAK MODULE. REMOVED AND REPLACED PARKING BRAKE VALVE, INTERCONNECT VALVE, LEFT AND RIGHT METERING VALVES. SYSTEM LEAK AND OPS CHK NORMAL PER MM32-41-00. NORMAL OPERATION OF SYSTEM VERIFIED ON TAXI CHECK.