Oil leaks on rear of C-145 engine

Aeronca Sedan Airplanes
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Oil leaks on rear of C-145 engine

Post by joea » Sun Jan 08, 2006 00:05

Helping Gareth with the annual on his Sedan and he has been having some issues with oil leaks around the rear of his engine. Its the "three bolt" C-145 engine, not the newer O-300 and he has already resealed the rear accy cover.

I was looking today and wondered if I saw some moisture coming out of the generator port tube.

Anyone else have problems in this area on a Sedan engine?


Joe A

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Joined: Tue Oct 18, 2005 13:55
Location: Port Townsend, WA

Post by zero.one.victor » Mon Jan 09, 2006 20:58

Typical leaks at the C-145/O-300 accessory case:

1) starter clutch (pinion) shaft on pull starter, this always seems to leak even after replacing the oil seal. This can run down the starter housing and make it look like the leak is coming from the mags, tach drive, or generator.

2) generator can leak oil, it bolts onto acc case so the drive end is exposed to oil pressure or at least oil splash. There is usually someplace under the generator drive gear assembly where an o-ring or two can be added to prevent this, on shaft &/or in between shaft and bushing(s).

3) generator/tach drive gasket. This one-piece gasket is often cut to facilitate replacement of the generator portion only. I cut mine, no leaks, but have heard of leaks from others. There's also a seal or packing on the tach drive cable.

4) Oil filter adapter (F&M/El Reno) is notorious for leaking at the adapter/acc case connection. The adapter needs to be torqued to 65 ft-lbs.The earlier adapters used a crush ring at this connection, F&M's later design uses a fiber gasket that seems to leak less. F&M'll sell you one for about 10 bucks + S&H.

5) make sure the temp gauge probe flange matches the seat in the adapter bushing used to install the probe at the oil pressure screen or filter adapter. Scott changed the probe flange on their gauges from flat to beveled a few years ago, so if you use a new gauge and an old adapter bushing you'll have trouble sooner or later.

They include a new adapter in the package with the new gauge but they do NOT point out that the flange/seat profile on the new parts are different. The adapter bushing is definitely needed, as the seat in the bushing is what the probe flange seals against. The probe can be installed in a seemingly-correct manner directly into the filter adapter (don't ask me how I know), but it's only a fluke if it doesn't leak when you check-run it. It WILL eventually leak (again,don't ask me how I know). :oops:


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