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Observations about oil leaks
I bought a PA-24-260 with a verrry slow leak from the prop governor.
This has taught me some things about oil leaks. 1) Oil does not go in the obvious direction. Even after you take into account the general airflow around the engine compartment and baffling there are local variations that make it hard to see how oil from point A can get to point B (without touching anything in between!). 2) Oil can move verrrry slowly. When I got the plane the only external sign of the leak was a fan on the pilot's side of the windshield (the governor is at the left front above the oil cooler). A few weeks later (and many flights a bit of oil would creep out from under the dipstick access hatch. For a long time I thought that was a second leak, but even after an oil change it was very dirty oil, and then I realized it was the oil that didn't sneak out the front of the cowling and instead slowly ran backwards on the underside until pressure forced it through the gap (other clues included the oil door itself being clean). If you wipe the bottom of the cowling off it goes away for a few hours. 3) One oil leak can come out multiple places (see (1) above) and at different times (see (2) above) and look like multiple leaks. 4) A slow leak that is doing something like oiling the windshield and irritating you may be mitigated by cleaning off the path from the leak to the windshield. The oil that actually gets to the windshield may be actually *leaked* on a different flight, and due to (2) moved oh so slowly into position to get in your way. In the case of the governor it seems to leak slowly onto the plate that the prop control rotates and is blown off from there. -- Ben Jackson http://www.ben.com/ |
#2
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1) Oil does not go in the obvious direction.
Good post. And what you say is true with all fluids -- and all engines. This summer I had some engine work done on my motorcycle, and immediately afterward headed out for a 450 mile, three-day ride. (Dumb, dumb, DUMB.) At our second rest stop, my 10 year old daughter asked what that "green stuff " was under the motorcycle. Of course, it turned out to be coolant (this on a Goldwing), and it was coming out at an alarming rate. Being in the middle of B.F.E., I called Mary, had her hop on-line and find me the closest Honda dealer -- which turned out to be in Dubuque. The leak was coming out of the lower left, front portion of the engine. Due to the extensive cowling on a Goldwing, I couldn't find the exact source of the leak, and ended up adding water every 15 minutes until we got to the shop. After de-cowling the engine, the mechanic found the leak at a hose connection -- on the TOP RIGHT portion of the engine! I would not have found that leak in a hundred years -- it was traveling across the engine, and down the opposite side, before dumping on the ground. We had a similar problem with a minor leak on the right side of our engine. It was coming out of the "gills" on the lower right side of the cowling, just a small line of oil that would stream back after some (but not all) flights. The leak turned out to be coming from one of the valve covers on the TOP of the engine. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#3
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My best luck in tracing oil leaks on aircraft engines
has been to clean the engine with Stoddard solvent, dry it with compressessed air, or otherwise let it dry. Wait until night and pull the aircraft outside to where it is nice and dark. Using a Black Light (uV lamp), inspect the engine. Oil fluoresces, so note any oil residue not removed by the cleaning, or which may have seeped out while the engine was being dryed. Run the engine at slightly above idle for one minute. Keep the draft from the prop at a minimum while doing so as not to spread the oil around much. Shut it down. Use the Black Light lamp to check for new fluorescence. Leaks that occur only while oil pressure is present should show up during the first short run. If you dont see a leak, then run the engine for a few more minutes, and look again. Oil leaks that are a consequence of splash lubrication might require running the engine longer or at higher rpms. This method is particulary helpful in spotting leaks around through-bolts, cyl base seals, crankshaft seal, accessories on their mounting pads, etc. MikeM |
#4
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Great post,
This is the same way, we in the coating inspection industry, check for oil on the surfaces to be painted or blasted if suspected. I found after more than a few minutes of High intensity UV light on the surface, I needed to wear UV glasses or the eyes burned. Pat Thronson |
#5
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"Jay Honeck" wrote in message
Being in the middle of B.F.E., I called Mary, had her hop on-line and find me the closest Honda dealer -- which turned out to be in Dubuque. BFE? |
#6
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