Oil leak....Alternator?

[Richgj3]

My 170B sat for 13 years until I bought it. Lots of work to get it flying again but all has been good. I have about 45 hours on it since June. The engine was majored about 250 hours ago, but many years (1991). It’s developed a small oil leak. The oil is on the bottom of the alternator and it does not appear to be coming from above. The mags were OH’d at the recent annual and new gaskets installed.

The local A&P will look tomorrow, but I wondered what you guys think. The rest of the engine is dry. I have the oil filter conversion. The alternator has not been off since 91. It was OH’d then. I’m assuming a seal has failed. The leak is getting worse. At first it was tough to see where the oil drop on the cowl lip was coming from.

Rich

[GAHorn]

The C145/O300 accessory case generator (alternator) mounting “pad” is a very common area of oil leaks on this engine. It is an area “submerged” beneath the oil-sump-level.
The next most common area is pushrod tube “rubbers” at the base of the pushrod tubes, followed by rocker-box covers.
The pull-starter pinion shaft is common also.

Continental oil leaks are a defense to corrosion and are almost as much a badge-of-courage to horizontally-opposed engine owners as the ones of radial engines. The only thing worse than a Continental oil leak is a Lycoming oil leak ... which more commonly results in engine failure (due to the abundance of eternal oil lines on Lycomings.)

[Richgj3]

Thanks. Those other spots you describe are dry. I did suspect the starter earlier but it’s dry. I used to own an airplane with a Continental W-670 Radial on it. It was described as not leaking oil as much as it was “marking its territory “.

[johneeb]

Rich,
Do some searches here for threads that talk about being sure to replace the Generator/Alternator/Tach drive gasket as one piece, that is a known leak area.

[Hineywheel Bill]

I chased a leak in the same area for the longest time. Changed alternator/tach drive seal at least three times, mag seals, etc. It turned out to be the tach drive housing which had been over-tightened previous to me buying it. If you placed it on a flat surface there was a gap between the three corners that apparently got worse as it heated up. I sanded it down with 400 grit sand paper on a hard, flat surface until it was flat again and reinstalled it to correct torque. Hasn't leaked there since, that was about 150 hours back.

[Richgj3]

John
Thanks. Just read through those threads. I even read Bill’s post about the uneven tach drive.
We will look tomorrow

Rich

[Richgj3]

So, in process of looking at where or if the leak is due to the alternator I noticed oil on the bottom of the oil filter. Turns out there was no clearance between the filter and the bottom of the battery box (inboard lower corner) and it wore a pin hole in the filter. Repositioned the adapter slightly to give good clearance. I knew this was close, but I thought it was ok. I forgot the engine moves and the battery box doesn’t.

As far as the alternator goes, I’m still not sure where it is coming from but I’m positive it’s not coming from above. Everything is washed down clean so we can see better. Honestly it doesn’t look like it’s coming around the gasket so that leaves the seal, but I can’t see any evidence of oil on anyplace I can see inside the alternator. If it continues we should be able to spot it now.

More to follow, I’m sure.

[GAHorn]

If it’s the FM-Emterprises/El Reno/Tempest oil filter adaptor it’s installation instructions specify clearance from adjacent object of at least 1/2”.

[Richgj3]

This is the Floyd Jones STC SE8409SW. Distributed by El Reno. Installed in 1993 but only less than 200 hours since. It has over 1/2 inch clearance now. I’ll be sure to keep an eye on it. I just looked through my paper work and found the directions regarding the clearance.