After washing my O-300 down with mineral spirits, I have spotted my oil leak After a short 5 minute run, I saw an oil track down the side of the FM oil filter head. Looking close to see whether it was the filter head or something above, I saw the telltale drip hanging off the generator shaft flange. The filter head washers were dry. The generator mounting flange is dry, only the shaft flange is wet with oil...indicating to me the shaft seal is bad. This was a new generator installation just prior to my buying the plane this past summer I do not yet have the O-300 parts catalog and was wondering what parts I am going to need to replace the shaft seal at next oil change. I know I need the mounting gasket for the drive case, and the shaft seal itself, but is there anything else I need? Any advice from those that have repaired this type of oil leak?
You will need the gen/tach housing gasket, the tach drive seal, and the gen drive seal. Be careful with the gen drive seal that it isn't damaged by the woodruff key on the gen shaft. The SRAM (available from TIC170A headquarters) has an article about this. Sacramento Sky Ranch also has some infor about it at their website and in person by phone.
Do not try to cut corners by altering the mount gasket or by not changing the tach drive seal. You will regret it. (read my article about my trip to the convention- "My 34th TIC170A Convention Trip" found in the Pilot Lounge.)
Last edited by GAHorn on Mon Nov 04, 2002 5:27 am, edited 1 time in total.
Unless the generator was RTV'd,you may not need to replace the gen/tach drive gasket.
I had (have) a similar leak from the alternator on mine. I pulled the alternator & had the local electrical shop who rebuilt it fix (or try to fix) the leaky shaft. Supposedly,it can't be leaking now,but I guess no-one told the oil that. It is leaking less than before,not enough to be a problem,just enough to be annoying. I'll pursue a fix in the future sometime.
Don't forget,the oil level in the sump is higher than the generator hole in the access. case when the airplane is in a 3 point stance. Don't ask me how I discovered that,even though I already knew it.
Ever notice how a quart of oil looks like about 2 gallons when it's puddled up on the hangar floor?
Thanks again George! I really wish I had a good manual for the O-300 that shows the parts you are talking about. I always like to rehearse in my mind what I am going to do out there on the ramp...especially when it is cold and windy I was going to get the Continental Overhaul Manual, but then saw the price and thought I could get by without it for now. Is this the manual I should have, or does the O-300 operations manual have a usable "blowup" diagram of the engine How about parts sources for internal engine parts like seals....what is the best one to use
wa4jr wrote:Thanks again George! I really wish I had a good manual for the O-300 that shows the parts you are talking about. I always like to rehearse in my mind what I am going to do out there on the ramp...especially when it is cold and windy I was going to get the Continental Overhaul Manual, but then saw the price and thought I could get by without it for now. Is this the manual I should have, or does the O-300 operations manual have a usable "blowup" diagram of the engine How about parts sources for internal engine parts like seals....what is the best one to use
John, I purchased a generator manual off of ebay a few months back. If you think it has what you are looking for, let me know and I will copy the pages and get them to you.
After a short 5 minute run, I saw an oil track down the side of the FM oil filter head. Looking close to see whether it was the filter head or something above, I saw the telltale drip hanging off the generator shaft flange. The filter head washers were dry. The generator mounting flange is dry, only the shaft flange is wet with oil...indicating to me the shaft seal is bad. This was a new generator installation just prior to my buying the plane this past summer 
I do not yet have the O-300 parts catalog and was wondering what parts I am going to need to replace the shaft seal at next oil change. I know I need the mounting gasket for the drive case, and the shaft seal itself, but is there anything else I need? Any advice from those that have repaired this type of oil leak?
How about parts sources for internal engine parts like seals....what is the best one to use