IO-390 front crankshaft seal leak?

[glider_rider]

My IO-390 EXP 119 reached 150 tach hours and since 30 maybe 50 hours the engine is leaking oil from somewhere in the front, not quite sure what's leaking, looks like it's the front crankshaft seal. Oil drifts down and aft, a few drops here, a few drops there.
Is there any clever way to have a good look at the crankshaft without removing spinner and prop?
How safety critical would be such a leak?

 

[wcalvert]

My Aerosport Power engine (IO-360) did the same thing early on. I was super aware of any leaks and noticed it after 50 hours or so. Wiped it down a couple of times and it hasn't returned... no source ever found.

This isn't a diagnosis but engine oil gets all around under the cowl and can end up it some pretty weird places. When you warm up the surface the oil moves even more. The drop may be no where near the source.

So maybe just wipe it down and keep an eye on it. Also take a good look around on the inside of your cowl and exhaust exit for any signs of oil on the belly etc.

Fly on!

 

[Avanza]

If it were my engine I would clean it of, fly for an hour and see if there is more
oil in the same place. You also get a feel for the how much it leaks.
Most engines have small leaks, it takes time to find where it leaks.

Good luck

 

[Jetmart]

Are you seeing an oil mist on the canopy? This is usually a sign that it potentially is a crank seal. If not I would suggest doing what the others have recommended. If you have too much oil spattered around after a short flight than do very short ground runs with the cowling off to find the source. I had a 110 hr 390 and was seeing leaks from a couple of case bolts along the top seem. The oil would drip down through the cylinder fins when sitting than blow out the bottom cowl. It took 25 hrs between oil changes for me see it. Very slow leak but a little oil makes a big mess. I was able to seal it up using Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant. I removed the bolts one at a time, cleaned the surfaces with alcohol, then applied liberal amounts to bolt hole and bolt. Then reinstalled.

https://www.amazon.ca/Permatex-8001...ocphy=1002451&hvtargid=pla-492732657309&psc=1

 

[Atanyspeed]

I had the same signs at 65 hours on my IO-390. Found oil all around the underside of the starter ring. Decided to pull the prop and pull the front seal. Found a nick on the seal. Replaced the seal and o-ring seal on the prop. No leaks after 5 hours.

 

[Ron B.]

My friend had to replace his seal also on his I0-390 EXP.

 

[Brucelan]

I had this problem too on my IO-390 Thunderbolt

It turned out there is an oil journal on front end of the case (on the #1 cylinder) that is plugged for this engine.

This was a brand new engine.

I would get a fine mist of oil on the engine in the right front area after a short flight, but nothing when I ran it on the ground. Apparently, the oil pressure was only high enough to cause the problem when i was running it at high power settings.

My A&P figured it out and replaced the plug with a more robust plug that Lycoming supplied him and I have not had the problem since.

bruce

 

[Zero4Zulu]

Where does your breather tube exit? I had mine terminating above one of my exhaust pipes but it was too far up in the engine compartment and was pressurized, which caused my right mag to develop a leak and my oil return lines were leaking also. Front seal could have been next had I not found the problem which was pointed out to me by Aircraft Magneto Service.
I extended my breather tube outside of the cowl and now have no leaks.

 

[glider_rider]

many thanks for all replays, l feel somewhat better knowing that my problem is not unique
breather tube is installed as per construction manual, but I will double check that. thanks again!

 

[tturner]

I had an oil leak in the front of my IO-390 that took me a while to find. Mine was leaking where the prop governor attaches to the engine. I isolated it by wrapping paper towels around the prop governor attach point and putting a tie wrap around the towels.