As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED DURING STRAIGHT TAXI TO LOADING POSITION, THE LT BRAKE PEDAL WENT TO THE FLOOR 3 TIMES. THE ACFT WAS SHUTDOWN AND SECURED AND THE PILOT CALLED MX. 30 MINUTES LATER, THE PILOT CALLED AND REPORTED THE LT BRAKE OPERATED NORMALLY. MX REPLACED THE LT MASTER CYLINDER WAS REPLACED AS A PRECAUTION.