A DHC8-100 DIVERTED DUE TO LOSS OF #2 ENG OIL PRESSURE AND QUANTITY. CAUSED BY IMPROPER INSTALLATION OF V BAND CLAMP DURING STARTER GENERATOR CHANGE.

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THIS IS AN ACCOUNT OF EVENTS AND ACTIONS RELATING TO THE DIVERSION OF ACR X ON OCT/MON/06 AT XA00 HRS. THE COMPANY MAINT SOFTWARE PROGRAM SHOWS A LOGBOOK ENTRY ON OCT/MON/06: 'DURING CLBOUT AND CRUISE FLT #2 ENG OIL PRESSURE SHOWED RAPID FLUCTUATION AND DECREASE IN PRESSURE. CREW VERIFIED OIL LEAK #2 NACELLE INFLT.' THE CORRECTIVE ACTION BY MAINT WAS ENTERED AS: 'INSPECTED AND FOUND #2 GENERATOR (STARTER/GENERATOR) LOOSE ON PAD. RE-SECURED AND SVCED WITH 5 QTS OIL. RAN ENG; STILL LEAKING FROM PAD. NOTIFIED SUPVR. SENDING MECHS OUT OF ZZZ1 WITH PARTS.' THE CORRECTIVE ACTION FOLLOWS AS: 'R&R (REMOVED AND REPLACED) STARTER/GENERATOR GARLOCK SEAL AND STARTER/GENERATOR OPS AND LEAK CHK GOOD PER WORK CARD 24-30-02R.' IN ADDITION; THE STARTER/GENERATOR 'V' BAND CLAMP WAS R&R'ED AS WELL. I WAS THE MECH WHO ACCOMPLISHED THE GARLOCK SEAL R&R CALLED FOR BY THE ATA CHAPTER 79 ENTRY DATED SEP/THU/06; 'REPLACE STARTER/GENERATOR GARLOCK SEAL.' IT APPEARS THAT INCORRECT MAINT PROCS WERE FOLLOWED. IN THE PROCESS OF DOING STEP 11 OF WORK CARD 24-30-02R; I CHKED THAT THE NUT ON THE 'T' BOLT OF THE V BAND CLAMP WOULD NOT TURN OFF OF THE END OF THE BOLT; BUT DID NOT VERIFY THE NUT HAVING FULL THREAD ENGAGEMENT WHEN HAND TIGHTENED. I DID TORQUE THE V BAND CLAMP NUT TO 70 INCH/LBS WITH MY PERSONAL TORQUE WRENCH. ALSO; IN THE PROCESS OF STEP 12 OF WORK CARD 24-30-02R INSPECTION OF THE CLAMP IS CALLED FOR: '...BY INSPECTING AROUND THE CLAMP USING AN INSPECTION MIRROR AS NEEDED AND BY APPLYING HAND FORCE TO CHK FOR LOOSENESS.' MY VISUAL INSPECTION OF THE OUTBOARD TOP OF THE CLAMP; OUTBOARD SIDE AND BOTTOM OF THE CLAMP WAS DONE; BUT I FELT THAT MIRROR INSPECTION WAS NOT NEEDED. HAND FORCE WAS APPLIED AND NO LOOSENESS WAS NOTED. THE GARLOCK SEAL R&R AND THE STARTER/GENERATOR R&R BOTH PASSED LEAK CHK AND OP CHK AS REQUIRED IN WORK CARD 24-30-02R AT STEP 16. IN AS MUCH AS THE OIL LEAK WAS NOTED DURING FLT; THE V BEND CLAMP NUT MUST HAVE LOOSENED DURING USAGE OF THE ENG #2 BTWN MAINT AT ZZZ1 AND XA00 HRS NEXT DAY. UPON INSPECTION AND RE-SECURING THE V BAND CLAMP; WHEN LEAK/OPS CHK WAS PERFORMED; 'OIL STILL LEAKED FROM PAD' NECESSITATING A MECH/PARTS ROAD TRIP FROM ZZZ1. THE FINAL CORRECTIVE ACTION WAS TO R&R BOTH THE GARLOCK SEAL AND THE STARTER/GENERATOR AS WELL AS THE V BAND CLAMP. IN RETROSPECT; I FIND THAT THE REQUIREMENTS OF WORK CARD 24-30-02R STEP 11 ARE VAGUE IN THAT THE NUT NEEDS TO HAVE RUNNING TORQUE FOR THE LENGTH OF THE 'T' BOLT; NOT JUST 'SUFFICIENT TO PREVENT FULL THREAD ENGAGEMENT WHEN HAND TIGHTENED.' I WILL DO SO IN THE FUTURE WHEN I R&R V BAND CLAMPS OF THIS NATURE.