What was found
DURING CRUISE FLIGHT, PILOTS OBSERVED NR1 ENGINE OIL PRESSURE FLUCTUATIONS. PRESSURE SUBSEQUENTLY DROPPED TO 25 PSI. AT THAT TIME, PILOTS PERFORMED PRECAUTIONARY SHUTDOWN AND DIVERTED FOR PRECAUTIONARY LANDING. MX FOUND OIL LEAKING FROM FLANGE OF ADAPTER AT FUEL HEATER OIL OUTLET. O-RING OR EQUIVALENT IAW TFE731-3, IPC 73-10-04, FIG 3 ITEM 25D WAS FOUND TO BE PART CAUSING LEAK. FURTHER INVESTIGATION OF O-RING FOUND IT TO BE CONFORMING TO CLAMPED PROFILE, BUT STILL SOFT/SUPPLE. INSPECTION BY BENDING THE O-RING REVEALED CRACKING OF THE MATERIAL. FAULTY O-RING AND OTHER SEALS REMOVED FOR ACCESS WERE REPLACED WITH NEW AND SUBSEQUENT RETURN TO SERVICE CHECKS WERE NORMAL. ENGINE REQUIRED 5 PINTS OF OIL TO REACH NORMAL OPERATING LEVEL. TIME SINCE INSP NOTED BELOW IS TIME SINCE "MAJOR PERIODIC INSPECTION."