As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST ALL HYDRAULIC BLUE SYSTEM FLUID. LOW PSI, LOW RESERVOIR WARNING LIGHTS. MAIN PUMP LOW PRESSURE INDICATION FOR BLUE SYSTEM. RETURNED TO SFO. REPLACED LEFT NACELLE FLAP ACTUATOR PER MM 27-50-00 AND CHECKED BLUE SYSTEM HYDRAULIC FILTERS. ALL CHECKS GOOD.