[STEVE]

STEVE on September 26, 2022 at 11:10 am #21578

Hi William;
Are these “weird off beat” oil leaks originating from the vicinity of the oil pressure switch? As I mentioned in my original post, dye penetrant developer spray, or athlete’s foot spray (the powdery kind) is a great leak location discovery tool.
As to why you look would show up after you’ve shut down, about the only thing that makes sense is that the leak might be coming from the oil pressure gauge–because it has a bourdon tube inside that might be sorta stiff so it may take the tube a few minutes to return to zero. If this is anywhere near logical, the tube does have oil under pressure inside; perhaps a slow return to zero could generate enough pressure to generate a leak.
Unfortunately, that does not explain why there’s no leak during engine operation.
Keep an eye on it, I’ll ask around for tips on this kind of leak
Sorry I don’t have a better answer.

S

[William]

William on September 25, 2022 at 11:28 am #21577

Thanks, Steve. It ended up being the oil pressure switch. Once it was replaced, the problem was resolved.

After leaving my original post, the leak occurred two more times. The strange thing is that it never happened with the engine running. In fact, the leaks were occurring somewhere between a few hours and 2 full days after running the engine. While I don’t want to go looking for trouble, the engineer in me wants to know why that would happen.

[Mark]

Mark on August 14, 2022 at 4:56 pm #21486

Once upon a time the transducer for my Hobbs meter leaked oil. Unfortunately my mechanic replaced it before telling me about it. I would have had him remove it completely.

[STEVE]

STEVE on June 25, 2022 at 9:22 am #21449

Hi William,
There shouldn’t be any oil leaks at all, especially behind the firewall.
The only part of the oil system that is aft of the firewall are a small tube that carries oil under pressure to the oil pressure gauge, and an oil pressure sensing unit (I believe it’s there to turn on the low oil pressure light in the annunciator panel on).
As you point out, access to the gauges and oil pressure system between the firewall and panel is difficult.
Common problem spots are any connection such as the tube to the gauge, the tube at the firewall, and the connection at the OP sensor.
You describe what sounds like quite a bit of oil, but on thing to remember, a teaspoon of oil at 180 degrees normal operating temperature will look like a lake.
Just about the only thing I can suggest is to remove the seat for better access, then thoroughly clean every connection, the sensor and the back of the gauge.
On thing that is effective and pretty easy to use is the cleaner spray that is part of a die penetrant kit. You can buy that at any welding supply store or from an aircraft supply house such as Aircraft Spruce (www.aircraftspruce.com) under the non destructive testing (NDT) heading.
After every thing at all the suspected locations is squeeky clean, a light coat of what’s called the NDT “developer” spray is applied. The developer is sorta like sticky talcum powder. It’s sprayed on then let dry.
Run the engine for a few minutes and any leakage will be easy to see against the white background of the developer.
Another tool that may be less expensive and easier to use is a flashlight with a “black light” bulb, or a “black light” bulb in a lamp. Oil shows up as a blue color under black light.
Let me know what you find.
Steve

[William]

William on June 25, 2022 at 5:22 am #21448

I own a 1977 Archer. I flew it on Monday for a little over an hour with no issues. This morning, I taxied to the fuel farm to top off the tanks and, when I exerted foot pressure to push my seat back, my foot skidded onto the rudder pedals like I’d stepping on a banana peel.

When I looked down, the rubber mat was partially covered in oil. It looked as though about 3-4 tablespoons worth. The maintenance director at the FBO came out and said there was a little oil on the oil pressure gauge transducer (senser). He said the fitting was tight so we started the engine (with the poor guy contorted under the panel) and nothing leaked.

I taxied back and put the plane in the hangar and pulled the top cowl cover. There was no evidence of oil anywhere. I did notice that several drops were on the hangar floor that morning. I haven’t leaked a drop of oil since my last overhaul in 2014. I left a paper towel on the pilot’s side floor where the leak was and after an hour, only 1 or 2 drops fell on the paper towel.

Has anyone encountered this? Is it simply a seal that needs to be replaced or do these things occasionally “burp” oil for no particular reason. The A&P didn’t seem concerned but if something isn’t supposed to leak oil – but does – I find myself on a mission to determine the cause and mitigate the issue.