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Best way to detect source of oil leak

Bavafa

Well Known Member
I have a strange situation going on which I see a streak of oil on top of the cowl about 3-4 inches from the center line on the co-pilot side that starts from the cowl?s very front to the back of it. This is the second time that I have seen this as the first time I thought it was residue of water from washing the canopy. I cleaned it just to see if it comes back, and sure enough it did after 3-4 hours of flying. It is of a very little amount, my guess about a couple of drops as you only see traces of it.
It does not seem to come from the spinner as I looked very closely and did not see any sign of any oil, also it would be strange that it has been exactly on the same spot. I took the top cowl off and could not find any trace or sign of oil on the inside of top cowl or baffle material that could have sipped thru. My guess is that it is coming from the bottom of the engine, perhaps due to excess pressure, and from the gap that exist between the cowl and spinner but again I did not find any trace of oil on the lip of the cowl.

So, I have a few questions for the gurus:

- Has anyone seen such thing or have any idea where this could be coming from?
- What is the best way to detect source of oil leak
- If I was going to wash and clean the engine what is the best method? I was thinking of covering the megs, battery, starter and alternator. Any other precautions that I need to be aware of?

Thanks in advance
 
clean the engine really well. I just used dry cloth rags to clean it up. put baby powder on the engine in the places you suspect the leak. I have had to cover my entire accessory cover before. Run it on the ground (or in air if it doesn't show up on the ground) and check for streaks in the baby powder. It will show up like a red thumb.
 
The dust from the cowl hinges wearing mixed with water does this. Very common, nothing to worry about. Its not oil.
 
The dust from the cowl hinges wearing mixed with water does this. Very common, nothing to worry about. Its not oil.

This was my first thought, but by the sound of the location, it doesn't appar to be near a hinge...

"I see a streak of oil on top of the cowl about 3-4 inches from the center line on the co-pilot side that starts from the cowl?s very front to the back of it"
 
Make sure you look at everything, not just the obvious stuff. I had a similar oil leak at the lip of the cowl inlet on the right side. It turned out to be a broken thru bolt that ties the #2 and #3 cylinders and the case halves together. I found the remaining piece of stud with the cylinder hold down nut still on it on top of the right side inter-cylinder baffle! I was able to replace the thru bolt without disassmbling the engine. The oil leak was gone.

Jerry
RV-8 N84JE
 
This was my first thought, but by the sound of the location, it doesn't appar to be near a hinge...

"I see a streak of oil on top of the cowl about 3-4 inches from the center line on the co-pilot side that starts from the cowl’s very front to the back of it"

Correct, my top cowl gets mounted with hinge on the sides but with screws on the top/back side and there is no hinge near the start or the end of this streak.

Is it safe to use the dye that they sell for automotive engines at auto stores in our engines? The kit in the amazon link seem to be for air conditioner.
 
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UV Dye

We had a tough leak to find and based on recommendations used the UV dye. It made finding the leak very obvious. Amazing how well it works. Read the info from the manufacturer. The bottle we used said A/C but it was good for any oil. You can get the dye at any auto parts store. I would recommend this flash lite,
http://www.amazon.com/LEDwholesaler...=UTF8&qid=1373384552&sr=8-2&keywords=uv+light

Cheaper and much better than the Auto Zone model we borrowed before this one arrived.
 
Dye

They sell dye at auto parts stores for both engines and a/c units, use the engine stuff of course. I'm pretty sure there is nothing special about a Lyc relative to using the engine dye and have done it myself and know of others who also have.
Ace hardware sells a nice little LED blacklight flashlight for finding pet stains that works just fine and cost about $10
I'm up at KRBL and looking for a very similar oil leak with no luck using the dye, this on a cozy with updraft cooling. I had thought it to be the push tube shroud leaking but have replaced everything there with no luck
Ill try powder next, but a broken through stud is now high on my list of concerns.
Tim
2013 dues paid
 
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I should add, just for more clarity, the trace of oil is on the exterior part of the cowl and no traces on the interior part. And I am wondering if it could be coming from the front seal?
 
Front seal oil leaks will follow the engine split and get the lower section oily after sitting static. It's the natural flow of air through the cowling to take it down and twords the back.
Lots of oil can reside in a hinge! I have been amazed at how much would settle in a Cherokee 140 hinge.

Back to baby powder on the suspected areas.
 
crank seal

Our leak was at the front seal. It seemed like there was no way that could be, as the front seam of the case under the nose was dry and clean. Our leak had oil coming out of the spinner gap and streaming back on the upper surface and some at the hinges. Amazing all the places air can go when under pressure. Oil could be seen on and thru the crank flange and we thought it was the CS prop O-ring.

Finally used the dye. It took 0.6 hours of hard ground running to get any oil to show up, but it finally did. The UV light showed the oil easily. The leak was not where the crank goes thru, but it was leaking around 75% of the seam between the case and crank.

Be warned that epoxy glows the same yellow as oil under UV. We had 2 drips of epoxy from my plenum and I thought I had 2 extra leaks for a few seconds. :)
 
Recently I had oil on the inner cowl of my SuperCub and everything was dry around it on the engine. It turned out to be a leaking valve cover gasket. I don?t see however how it could spit forward against the inlet, but you never know! Just a thought.
 
Our leak was at the front seal. It seemed like there was no way that could be, as the front seam of the case under the nose was dry and clean. Our leak had oil coming out of the spinner gap and streaming back on the upper surface and some at the hinges. Amazing all the places air can go when under pressure. Oil could be seen on and thru the crank flange and we thought it was the CS prop O-ring.

Finally used the dye. It took 0.6 hours of hard ground running to get any oil to show up, but it finally did. The UV light showed the oil easily. The leak was not where the crank goes thru, but it was leaking around 75% of the seam between the case and crank.

Be warned that epoxy glows the same yellow as oil under UV. We had 2 drips of epoxy from my plenum and I thought I had 2 extra leaks for a few seconds. :)

I am suspecting the same thing, only not sure if it is coming from the front seal or other area, though sure it is from the bottom part than the upper part. I will be using the dye to hopefully detect this and will report back.
 
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