What was found
APPROX. 1.5 HOURS INTO FLIGHT LT ENGINE OIL PRESSURE GAUGE STARTED SHOWING INTERMITTENT. ON DESCENT OUT OF FL370 OIL PRESSURE STARTED DROPPING SLOWLY, CONTINUED TO MONITOR THEN OIL PRESSURE WENT <30 PSI MASTER CAUTION. REMOVED STARTER CARBON SEAL P/N 3056647-2 AND RING AND INSTALLED NEW ONE P/N 3050647-2 AND NEW RING. REMOVED AIR STARTER, INSTALLED NEW AIRSTARTER. REMOVED OIL PRESSURE TRANSMITTER. PERFORMED GEAR BOX PRESSURE CHECK. FOUND SATISFACTORY. INSPECTED GEAR BOX FOR CRACKS AT OPERATING TEMP NO CRACKS NOTED AT THIS TIME. INSPECTED ENG FOR OIL LEAKS AFTER MAINT. NO LEAKS NOTED AT THIS TIME. ALL OPERATIONAL CHECKS FOUND SATISFACTORY AT THIS TIME.