Gaskets/Oil Leaks
Posted: Tue Apr 10, 2007 1:36 am
I continue my search for the proverbal needle in a haystack aka oil leak source 
I need some expertise from some of you mechanic types. On our O-300's the gasket that goes between the magneto and the accessory case (p# 535324) has, two holes in it for the mounting stud bolts to go through and each one has a brass (?) grommet . If there is a tear between the grommet and the outside of the gasket (from the stud out toward the outer edge), would this likely cause an oil leak? If so and the damaged gasket area is on the upper magneto stud, just above the left hand, lower stud of the tachometer drive housing, could that oil then be running down onto the tach drive housing stud making it appear the tach drive housing was the source for the leak? This is in an area that is difficult to observe due to all the components being so closely mounted. I realize its a long shot, but I can find no reason for the oil to be leaking from the tach drive housing mounting area down onto the alternator. No leak at the tach drive Garlock seal either. The area where the tach drive housing and alternator mate to the accessory housing has been cleaned & recleaned. Each time a new gasket has been used, sometimes with Tite Seal and most recently with aviation Permatex and I get the same leak when the oil temp gets up to about 140 degrees. No "apparent" crack in the accessory housing.
I need some expertise from some of you mechanic types. On our O-300's the gasket that goes between the magneto and the accessory case (p# 535324) has, two holes in it for the mounting stud bolts to go through and each one has a brass (?) grommet . If there is a tear between the grommet and the outside of the gasket (from the stud out toward the outer edge), would this likely cause an oil leak? If so and the damaged gasket area is on the upper magneto stud, just above the left hand, lower stud of the tachometer drive housing, could that oil then be running down onto the tach drive housing stud making it appear the tach drive housing was the source for the leak? This is in an area that is difficult to observe due to all the components being so closely mounted. I realize its a long shot, but I can find no reason for the oil to be leaking from the tach drive housing mounting area down onto the alternator. No leak at the tach drive Garlock seal either. The area where the tach drive housing and alternator mate to the accessory housing has been cleaned & recleaned. Each time a new gasket has been used, sometimes with Tite Seal and most recently with aviation Permatex and I get the same leak when the oil temp gets up to about 140 degrees. No "apparent" crack in the accessory housing.