We ran Rodney's overhauled engine for the first time today. Bloke came up with a procedure for checking everything out during the test run. After Rodney shut down, it was obvious there was an oil leak. We took it back into the hangar and started investigating. It looked like it could have been coming from the prop seal. The oil was isolated to the far forward starboard side of the engine. We looked all over and cleaned things up to have another go at the problem. Bloke stuffed a rag in a position to see if oil could be coming from the prop seal. There was much speculation about the source based on our notions of which way the combination of airflow and gravity would be working. So back outside for another test run.

I was watching the area with the leak very carefully. A lot of the possible sources of the leak were hidden from view because of baffling and other stuff. I was watching in particular the forward plug on the starboard oil gallery which didn't look just right during all the engine installation. As the engine ran I noticed a small stream of oil coming from that plug and running forward (yellow arrow). One would have thought with the prop blast it would run back, but it didn't. It must have been between two forward moving air flows because it stayed in a nice little river until it hit the baffling.

So it was back inside where we found that the plug had been cross threaded. We cleaned up the plug (steel) which was in perfect condition and cleaned up the hole (aluminum) which had some damage. We reset the plug and tightened it. Outside for a test, and there was still a leak. What do you do with a pipe thread? Tighten it some more. And sure enough the leak was stopped. Chasing down oil leaks can be a challenge. Fortunately, the rest of the engine was leak free.