In case any UL350iS operator is wondering...this is what a front seal oil leak looks like...maybe! Still figuring it out.

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Comment by Roger E Barnes on December 18, 2019 at 5:19pm

wow sorry to see that Dave, best of luck with repairs. 

Comment by Jerold Ebke on December 18, 2019 at 11:19am

I had a local mechanic come out to the hanger and with various pullers and some use of screw drivers and prying / pushing, the bearing came off fairly easily. I just needed a copilot for that portion of the flight to make me feel safer.

Used a bearing driver to seat new one. No problem.

I had oil in that area just as your picture shows.

Comment by David J. Beaulieu on December 18, 2019 at 8:48am

Jerold, the situation you describe is almost exactly what I have on hand with this!! In the process of redoing front seal and O-ring under the thrust bearing retention ring.  When disassembled, both items looked fine with nothing obvious which would contribute to a seep or leak.  Waiting on words from UL regarding removing the oil stop plug in the crankshaft end.  In the meantime, I will try to fabricate a suitable tool to facilitate removal.  Glad to know your technique worked for stopping the leak.  How easy to replace that front thrust bearing?  Thanks for posting, it does indeed help with getting my head wrapped around this issue.  Don't feel like the "Lone Ranger" anymore.

Cheers!  Dave

Comment by Jerold Ebke on December 16, 2019 at 12:32pm

David

I have an early 350i with the older black ECU ( for production  timeline idea ). I had what I thought was a very small front oil seal leak. When I disassembled, I had oil inside the threaded end of the crankshaft which was the only place I could see evidence of much oil. Was not very oily around the crankshaft seal itself. I had much less oil than your picture shows.

As you know, there is a threaded quarter sized flat plug with a large slot that seals the inner portion of the crank at a greater depth in the crankshaft than the end of prop flange mounting bolt installs to. That is where I believe I had oil coming from.

My engine was relatively clean on front and I do not believe oil could have migrated into this area from the front seal leaking. The leak had to be past the inner crankshaft end seal threaded into the crank.

I made a large flat screwdriver like tool to attempt to remove that plug and since it appears to be aluminum, all I did was proceed to mess up the slot in plug. I think the UL book says install with a sealer. It was tight enough I could not remove it, but seamed to be leaking minimally.

I went ahead with the front outer crankshaft seal replacement and cleaned up the inner threaded area of the crankshaft so it was oil free. I judiciously placed some oil resistant RTV sealant in the last 1/4 inch or so of where the prop flange bolt would screw in to at its maximum depth and reinstalled the flange bolt and the flange according to UL instructions. I hoped the threads of the prop flange mounting bolt turning into the sealant on the threads inside the crankshaft would be an adequate seal.

I also found the front thrust bearing noisy on rotation and replaced it as well.

My leak occurred at occurred at 292 Hobbs hours and I have 370 hours now with no evidence of recurrence.

This was my experience and I hope it may help you in some way.

I continue to have great faith in my engine.

Comment by David J. Beaulieu on December 16, 2019 at 8:08am

Thanks Robert, appreciate the comment!  I am hoping I can resolve the issue without pulling the engine.  The time of year and an unheated hangar does not make the issue any easier.  At least, I'm not sitting in a field somewhere!

Comment by Robert Riat on December 15, 2019 at 9:00pm

I like to think the UL engine is a good engine, but it seems you have had more than your share of problems.

Mine is a newer engine, but with about the same hours as you and, so far, I can’t say anything but good

about it. In my earlier years, I overhauled engines (as a part time business) and several of those with front

seals leaking were from out of tolerance front crank bearings.  We attributed the problem to over tight belts

running too many gizmos (ac compressors, smog pumps, etc.). Anyway, I hate seeing you are having so

many problems and hope it this doesn’t turn out to be serious.  You have a great looking plane and it

doesn’t deserve all the engine problems.

Comment by David J. Beaulieu on December 15, 2019 at 7:59pm

Robert, the original seal wasn't quite as bad.  This is a new seal I put in 8.3 hrs ago.  I've got it torn apart to try and figure out what's going on. Could be I screwed it up..don't know, but don't think so.  I've done lot's of rear seals on my old Landcruisers with no problems.  I think it's the oil stop in the end of the crank, but will try one more time.  Remember any task worth doing is worth doing twice ;)

Comment by Robert Riat on December 15, 2019 at 7:07pm

Is this leak from your original seal?

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