What was found
FLT 933 - GUM - NR 3 ENGINE OIL FILTER BYPASS LIGHT ILLUMINATED DURING CRUISE FLT AT FL 31. ALL ENGINES PARAMETERS WERE NORMAL. MX T/S SYSTEM AND REPLACED OIL FILTER AND O-RINGS, LIGHT REMAIN ON. CHECK OIL LINE AND VENT LINE FOUND NORMAL. REMOVED AND REPLACED BYPASS SWITCH PER MM 79-33-2. ENGINE RAN FOUND NO LEAKS OIL FILTER OR BYPASS SWITCH PER MM 79-33-2. ENGINE RAN FOUND NO LEAKS OIL FILTER OR BYPASS SWITCH. LIGHT OPERATES NORMAL AND OPERATIONAL CHECK GOOD. AIRCRAFT RELEASE FOR SERVICE. (M)