What was found
PDX - UPON LOWERING THE GEAR FOR LANDING, THE CREW RECEIVED AN AMBER GEAR DOOR LIGHT AND HYDRAULIC FLUID LOSS AND PRESSURE FLUCTUATION. THE CREW COMPLIED WITH EMERGENCY PROCEDURES, SHUT DOWN AND WAS TOWED TO THE GATE. MAINTENANCE INSPECTED THE AIRCRAFT AND FOUND A CAP ON THE HYDRAULIC MANIFOLD LEAKING. THE O-RING ON THE CAP WAS REPLACED, THE SYSTEM WAS SERVICED, AND A OPERATIONAL CHECK WAS PERFORMED. THE OPERATIONAL CHECK WAS GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.