A B747-200 MADE AN UNSCHEDULED STOP DUE TO #4 ENG LOSS OF OIL QUANTITY AND PRESSURE CAUSED BY THE IMPROPER INSTALLATION OF THE #4 ENG STARTER DRIVE CARBON SEAL.

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TO THE BEST OF MY KNOWLEDGE; ON APR/XA/99 ON ACFT XYZ #4 ENG I INSTALLED THE NEW CARBON SEAL ASSEMBLY; LEFT FROM THE PREVIOUS SHIFT; PER MAINT MANUAL 72-61-06. I THEN OPS CHKED THE ENG BY DRY MOTORING AND FOUND NO LEAKS. HOWEVER; LATER I FOUND OUT THAT ACFT XYZ DID AN UNSCHEDULED STOP IN WXZ DUE TO OIL CONSUMPTION ON #4 ENG. WITH SOME RESEARCH; I REALIZED THAT I HAD NOT INSTALLED THE CARBON SEAL ASSEMBLY PROPERLY; BUT JUST 2 PARTS OF A 3 PIECE ASSEMBLY. THE PREVIOUS WORKSHIFT TO MINE HAD REMOVED THE OLD CARBON SEAL ASSEMBLY AND EITHER DISCARDED OR MISPLACED IT. I WAS GIVEN THE JOB TO INSTALL THE NEW CARBON SEAL ASSEMBLY. I FOUND THE NEW ASSEMBLY SITTING IN THE WORK AREA AND INSTALLED IT PER ACR MAINT MANUAL 76-61-06 ITEM 5C (WHICH WAS CALLED OUT FOR ME TO USE) NOT REALIZING THAT I WAS INSTALLING AN INCOMPLETE ASSEMBLY. INSTEAD OF THE WHOLE ASSEMBLY BEING ORDERED; THE PARTS WERE ORDERED INDIVIDUALLY. THE ACR MAINT MANUAL 72-61-06 FOR CARBON SEAL REMOVAL/INSTALLATION DOES NOT COVER THE ASSEMBLING OF THE 3 PIECES INTO THE COMPLETE ASSEMBLY. THE BOEING MAINT MANUAL 72-61-06 DOES THOUGH. HAD I REMOVED THE OLD SEAL OR AT LEAST HAD THE OLD ONE TO COMPARE THE NEW ONE TO I WOULD HAVE NOT MADE THIS MISTAKE. I FEEL THAT THE BOEING MAINT MANUAL 72-61-06 SHOULD BE INCORPORATED INTO ACR MAINT MANUAL 76-61-06. BY DOING SO MAY PREVENT THIS FROM HAPPENING AGAIN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE JOB WAS WORKED FROM AN INSPECTOR'S WRITE-UP AND WAS REQUIRED TO BE INSPECTED PRIOR TO INSTALLATION OF THE STARTER. THE RPTR SAID HE NOTED THE DIFFERENCE BTWN THE COMPANY MAINT MANUAL WHICH DOES NOT REQUIRE INSPECTION AND THE BOEING MAINT MANUAL WHICH REQUIRES INSPECTION. THE RPTR SAID THE PROB WITH THE SEAL INSPECTION IS 2 COMPONENTS ARE COVERED BY A SEAL REGAINING PLATE AND NEEDS AN EXPERIENCED INSPECTOR TO IDENT THE 2 COVERED COMPONENTS.