Narrative:

At approximately XA30; received a call to go to aircraft X to check out an oil leak on #1 engine. I ran #1 engine while mr X tried to locate the leak. We found the oil coming from the idg drive pad drain line. After consulting with maintenance control; it was decided that we would keep this aircraft for the charter flight to ZZZ1. We had some problem getting the idg to release from the gear box. After several mins we got the idg off and found heavy oil sludge coming down from the garlock seal on the gear box and deduced that that was the source of the leak. We incurred a few more mins delay in trying to ensure that we were installing the correct part number seal assembly. I installed the garlock seal assembly and then began installing the original idg. The original idg would not fully engage in the gear box. We made 4 or 5 attempts to get this idg in; then decided to try another idg. The replacement idg engaged easily and we continued the installation. We ran the engine and operations checked the idg. Leak checked the engine. No leaks noted. Disconnected the idg during the operations check then shut down the engine. Verified the idg oil was still at the proper level; then ran the engine a second time to verify the drive was properly engaged. Operations check was normal and no leaks noted. The aircraft departed approximately 30 mins late. I was back at the maintenance office cleaning up some time after the aircraft had left when I realized that I was not absolutely sure that the replacement seal assembly had come with o-rings installed. I asked mr X if he had checked for the o-rings; and he didn't recall checking for them either. As we had run the engine twice and found no leaks; we deduced that the o-rings must have been installed but decided to check the aircraft when it returned to ZZZ in the morning as a precaution. Later in the morning I received word the aircraft had diverted on the return trip due to declining oil quantity on #1 engine.

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Original NASA ASRS Text

Title: A B737-700 HAD #1 ENG IDG REPLACED DUE TO OIL LEAK. AFTER 1 FLT; ACFT DIVERTED DUE TO LOW OIL QUANTITY #1 ENG.

Narrative: AT APPROX XA30; RECEIVED A CALL TO GO TO ACFT X TO CHK OUT AN OIL LEAK ON #1 ENG. I RAN #1 ENG WHILE MR X TRIED TO LOCATE THE LEAK. WE FOUND THE OIL COMING FROM THE IDG DRIVE PAD DRAIN LINE. AFTER CONSULTING WITH MAINT CTL; IT WAS DECIDED THAT WE WOULD KEEP THIS ACFT FOR THE CHARTER FLT TO ZZZ1. WE HAD SOME PROB GETTING THE IDG TO RELEASE FROM THE GEAR BOX. AFTER SEVERAL MINS WE GOT THE IDG OFF AND FOUND HVY OIL SLUDGE COMING DOWN FROM THE GARLOCK SEAL ON THE GEAR BOX AND DEDUCED THAT THAT WAS THE SOURCE OF THE LEAK. WE INCURRED A FEW MORE MINS DELAY IN TRYING TO ENSURE THAT WE WERE INSTALLING THE CORRECT PART NUMBER SEAL ASSEMBLY. I INSTALLED THE GARLOCK SEAL ASSEMBLY AND THEN BEGAN INSTALLING THE ORIGINAL IDG. THE ORIGINAL IDG WOULD NOT FULLY ENGAGE IN THE GEAR BOX. WE MADE 4 OR 5 ATTEMPTS TO GET THIS IDG IN; THEN DECIDED TO TRY ANOTHER IDG. THE REPLACEMENT IDG ENGAGED EASILY AND WE CONTINUED THE INSTALLATION. WE RAN THE ENG AND OPS CHKED THE IDG. LEAK CHKED THE ENG. NO LEAKS NOTED. DISCONNECTED THE IDG DURING THE OPS CHK THEN SHUT DOWN THE ENG. VERIFIED THE IDG OIL WAS STILL AT THE PROPER LEVEL; THEN RAN THE ENG A SECOND TIME TO VERIFY THE DRIVE WAS PROPERLY ENGAGED. OPS CHK WAS NORMAL AND NO LEAKS NOTED. THE ACFT DEPARTED APPROX 30 MINS LATE. I WAS BACK AT THE MAINT OFFICE CLEANING UP SOME TIME AFTER THE ACFT HAD LEFT WHEN I REALIZED THAT I WAS NOT ABSOLUTELY SURE THAT THE REPLACEMENT SEAL ASSEMBLY HAD COME WITH O-RINGS INSTALLED. I ASKED MR X IF HE HAD CHKED FOR THE O-RINGS; AND HE DIDN'T RECALL CHKING FOR THEM EITHER. AS WE HAD RUN THE ENG TWICE AND FOUND NO LEAKS; WE DEDUCED THAT THE O-RINGS MUST HAVE BEEN INSTALLED BUT DECIDED TO CHK THE ACFT WHEN IT RETURNED TO ZZZ IN THE MORNING AS A PRECAUTION. LATER IN THE MORNING I RECEIVED WORD THE ACFT HAD DIVERTED ON THE RETURN TRIP DUE TO DECLINING OIL QUANTITY ON #1 ENG.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.