As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DIVERSION - ON CLIMB TO CRUISE "B" HYDRAULIC SYSTEM SLOWLY DECREASED TO "0" QUANTITY. DID NOT LOOSE "B" SYSTEM PRESSURE UNTIL FLAPS LOWERED ON APPROACH. REMOVED AND REPLACED "O" RING LEAKING ON PRESSURE SWITCH AT "B" SYSTEM HYDRAULIC MODULE PER MM.