What was found
(CAN) AFTER TAKEOFF, 1 ENGINE HYDRAULIC PUMP CAUTION LIGHT ILLUMINATED AFTER FLAP RETRACTION. THE HYDRAULIC FLUID QUANTITY INDICATION SHOWED 0.5 LITERS FOR THE NR 1 SYSTEM. THE ACFT HAD AN UNEVENTFUL FLAPLESS LANDING. MAINTENANCE PERSONNEL FOUND THE LEAK AT THE INLET TO THE NR 1 SYSTEM HYDRAULIC MANIFIOLD. THE UNION ON THE MANIFOLD FROM THE ENGINE DRIVEN PUMP LINE WAS FOUND TO BE CRACKED AND ALSO THE O-RING HAD BEEN CUT. A NEW UNION, O-RING AND ENGINE DRIVEN PUMP WERE INSTALLED AND THE ACFT RETURNED TO SERVICE.