Look at what showed up the other day from Oshkosh, WI. We think it is a pretty special deal to be recognized by the judges for the hard work we put into the plane. Scott’s standard response to anyone that asks where he learned to build with such good quality is that he “just didn’t know any better.” Looks like all the years of rebuilding motorcycles and cars paid off.
Tanya and I spent both days this weekend working on the sump gasket. Before installing the new gasket, I felt it was prudent to ensure, without a shadow of a doubt, that the machined parting surfaces on the case and sump were not the cause. I put down a very thin consistent layer of Prussian Blue on the sump flange. Then did a dry assembly without the gasket, then disassembled. What we’re looking at here is the dye stain pattern on both flanges. Imperfections show up pretty easily. Both flanges were perfect all the way around as expected. Ok, so that was my due diligence. We reinstalled a new sump gasket with a little Loctite 515 on both sides.
The rest is just a tedious reassembly process. Intake tubes back on with new gaskets, exhaust system back on with reused blow-proof gaskets, carb and airbox back on, all control linkages adjusted and checked, plus all the little details in between. Did I mention that it was 102 degrees outside? Once everything was triple checked, I pulled it out on the ramp and did a runup with the cowl off. No drips, runs great. We didn’t have enough energy left to cowl it back up and do a test flight. That will remain for another day.
Ok, time for comment on something I’ve been chasing for the last approx. 150 hrs.. I had been noticing more oil blowing around the right side of the engine. No major big deal, we still were not loosing more than about .5 qt in 25 hours. At the last oil change at about 400 hours, we put 7 quarts in and for whatever reason, left the cowl off until the next day to complete the operation. When we returned, there was a puddle about 3″ in diameter on the hangar floor below the #1 intake tube at the sump. Note, this was perfectly clean, never run oil, not from a spill. I traced it up to the sump gasket and no higher. Wow, that gasket was leaking. I did a real careful inspection of the area. Nothing was cracked, but it is very weird for a gasket to simply let go. This was just a few day before Oshkosh. Tanya and I discussed at great length over the course of a couple of day whether to pull the sump and install a new gasket before the cross country flight or to just go with it and deal with it when we got back. We went quite deeply through the risk vs. gain engineering cycle. I’m not comfortable at all with doing a whole lot of maintenance operations too close to launching off across the country. There just wasn’t enough time to do the operation AND get a few hours of local flight with subsequent inspection before heading to Oshkosh. We decided it had probably been in whatever state it is in for the last 100+ hours, and to just leave it for this trip, as opposed to tear into it and upset the status quo.
We talked with Mahlon at Oshkosh and he almost couldn’t believe the sump gasket had failed. I don’t blame him. I wouldn’t have believed it myself if I had not sat in the hangar and watched oil drain onto the floor from around the sump gasket. So, we returned from Oshkosh and I repeated the experiment. Yep, no question. This wasn’t even a problem of finding the leak. Put oil in, and immediately watch it drain out onto the floor.
With new gaskets in hand, I dove in and pulled the sump. It only took me a couple of hours in the 100+ degree heat to get the sump off. Of course, a whole lot of other stuff has to come off before. The sump came off cleanly with the gasket intact and stuck to the sump flange. To my surprise, the gasket was as pictured at the leak location. All of the pictured gasket material was still stuck firmly to the sump flange and was not disturbed during dis-assembly. Obviously I paused and inspected this very carefully. My conclusion is unfortunately, this sump was assembled with a torn gasket. Maybe I’m willing to accept that it wasn’t, and the gasket failed in place. That would seem to indicate that the part surface has issues. I’ll be testing the surface before reassembly. I’m happy that I found a real culprit and that I’m not just chasing down some phantom leak. I’ll have it all fixed up in another few work sessions.
