What was found
NR 1 ENG LOW OIL PRESS/FILTER BYPASS LIGHT CAME ON AT APPROX 0450Z FL240 CRUISE. OIL PRESS WAS 47 PSI QUAN AND TEMP NORMAL RANGE RETARDED NR 1 THRUST LEVER TO IDLE LIGHT REMAINED ON SHUTDOWN NR 1 ENG IAW CHECK LIST. LIGHT STAYED ON ABOUT 4 MINS AFTER ENG START BEFORE LIGHT GOES OUT. REMOVED AND REPLACED NR 1 ENG LOW OIL PRESS FILTER BYPASS SW. LEAK AND OPS CK GOOD. RAN NR 1 ENG PER JRH OIL LOW PRESS/FILTER BYPASS LIGHT OPS CK'D NORMAL.