As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, NR 4 HYDRAULIC SYSTEM DECREASED TO 4 GALLONS. ENGINE PUMP DPERSSURIZED QUANTITY CONTINUED TO DECREASE. AIRCRAFT TURNBACK JFK. REMOVED AND REPLACED ENGINE DRIVEN PUMP. PRESSURE FILTER AND CASE DRAIN FILTER PER MM 29-11-05 MM 29-11-18 AND 29-11-23. OPERATIONAL CHECK NORMAL. A/C RETURN TO SERVICE. (M)