As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 4 HYDRAULIC SYSTEM LOW QUANTITY LIGHT CAME ON AFTER TAKEOFF. DEPRESSURIZED ADP AND EDP QUANTITY STABILIZED AT 1.6 GALLONS. AFTER SYSTEM USED FOR LANDING QUANTITY RAISED TO 4.0 GALLONS THEN DROPPED TO 3 GALLONS AFTER LANDING. TIGHTENED LOOSE B-NUT ON SUPPLY LINE AT TOP OF PYLON, LEAK CHECK OK PER BOEING MAINTENANCE MANUAL 29-11-00.