What was found
CLIMBING THROUGH FLIGHT LEVEL 18, THE NR 1 ENGINE OIL PRESSURE DROPPED TO 35 PSI, OIL TEMPERATURE INCREASED TO 120 DEGREES. THROTTLE RETARDED, OIL PRESSURE REMAINED AT 35 PSI, OIL PRESSURE BEGAN TO RECOVER ON APPROACH TO INDIANAPOLIS AIRPORT. REMOVED AND REPLACED THE NR 1 ENGINE OIL PRESSURE RELIEF VALVE IAW PW MM 72-61-0, OPERATIONAL CHECKED NORMAL IAW PW MM 72-00. NO LEAKS NOTED AT THIS TIME, OK FOR SERVICE. (M)