[Charles]

Charles on November 7, 2025 at 5:43 pm #25656

On my 1965 PA28-180, after every flight a small trail of an oil leak appears on the right side of the cowling from the vent.  I have had the rocker arm gaskets replaced in the past and cannot see where the source could be coming from.
I have attempted to attach a photo of the leak. 
Has anyone had similar leaks or may know where I can start to solve this mystery leak??

 

Attachments:

• N5902WOILLEAK.jpg

[STEVE]

STEVE on November 7, 2025 at 8:47 pm #25657

Hi Charles;
You and your mechanic can attempt to find the source of the leak by getting a black light (portable or bulb for screwing into a 110 Volt light socket) and after dark shine the black light at the engine. Oil will show up as a neon green color.

FWIW, I had a very perplexing oil leak that I fought for a while. It turned out that the fabric cowling chafe strip ( https://www.aircraftspruce.com/catalog/cspages/cowlingchafeseal.php) had absorbed oil. When the engine was running the oil in the tape became more viscous and leaked slowly out. I changed the tape and my “leak” went away.

[Aaron Kahn]

Aaron Kahn on November 13, 2025 at 5:01 am #25663

I had a small leak develop once, and it was from the fitting where the rocker box oil return line connected to the small piece of rubber tubing before going back to the oil pan. There was some oil seeping out and around the joint with the rubber tube. I had to tweak/fiddle with the metal and rubber tubes a bit and that cured the problem.

Aaron

[James Grahn]

James Grahn on January 9, 2026 at 11:28 pm #25689

Lycomings are notorious for leaking. Steve’s suggestion is a good one (black light). You might want to wash the engine down, then run it for about ten minutes before you look for the leak.
Flying a plane will make the thin, hot oil go anywhere in the cowl. Just about everything on the accessory case has a gasket that can leak.