As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
KLCK/TJSJ - EN ROUTE, ALL MAIN HYDRAULIC SYSTEM QUANTITIES DROPPED TO THE STANDPIPE LEVEL. AN UNEVENTFUL LANDING WAS ACCOMPLISHED AT TJSJ, AND THE AIRCRAFT WAS TOWED BACK TO THE RAMP. INSPECTION OF THE AIRCRAFT REVEALED AN O-RING HAD BLOWN ON THE SLOT CONTROL VALVE. THE O-RING WAS REPLACED AND LEAK-CHECKED IAW THE DC-8 MM, AND THE AIRCRAFT RETURNED TO SERVICE. (X)