Bubblehead

My how time flies. I came across my link to this forum and thread and thought I'd post "the rest of the story." This oil leak problem occurred in 2016 and never re-appeared, so with the help of the posters we solved the problem. In fact, I flew this plane about 100 hours a year until early 2020 when I sold it. In 2019 I took the plane from Texas to Alaska and back on a month long vacation. The problem never appeared again. My thanks again to all who helped me troubleshoot it, come up with correction options and gave moral support.

Thanks for the info on the oversized stud. I did not go that route. I think putting an oversized stud in aluminum risks cracking the aluminum accessory case. I now have over 6 hours of flight time since installing the stud with Locktite 271 and there is not a hint of oil on the belly of the plane. I hereby declare success on solving the oil leak. My thanks to everyone who offered suggestions and information. I have learned a lot from this.

Just got home from a 30 minute test flight and there is no sign of a leak anymore. Rain prevented me from flying a second, longer flight but I feel very good about the Locktite 271 on the stud. My thanks to everyone who chimed in with information, opinions, references and even guesses. I consider this to have been a collaborative effort and a group success. I will update this thread in a couple of weeks if all continues satisfactorily and sooner if it doesn't.

He did not have a leak at the stud. His leak was caused by there not being the proper Lycoming-required .040 spacer plate installed.

We reinstalled the stud with Loctite 271 Wednesday night, and reinstalled the governor (with plate and gaskets!) last night and did a leak check. I ran the engine for about 5 minutes with the prop at high-rpm and warmed up the oil to about 140F. No leak. Slowly brought the prop lever back to raise pressure to the prop and perhaps put more stress on the system. Ran with about a 200 rpm drop for about 3 minutes and still no leak. We shut everything down, put the cowling on and I'll test fly over the weekend to see if the leak returns. At this point the results look promising.

jetdriven and carusoam - I stand corrected. Thank you for sending the link to the booklet. I learned a lot from that. I still doubt we're seeing 600 psi but I concede there is a pump. Oil pressure failure on my plane puts the prop in high-rpm (low pitch) condition. I may be wrong but wouldn't course pitch be better with engine failure? When a prop on a twin is feathered it is move through course settings until it is in the low drag position. Good conversation starter. Piloto - Good that you had it tested but don't forget to install the plate! I also had mine tested at a prop shop and there were no leaks although my relieve valve was relieving a bit low and they adjusted that. And baby talc is ok unless you use it frequently in places it doesn't belong. A lot of people raised a lot of kids using it before putting the diaper on without problems. General comments on several posts. First, thanks for all the great information and even the opinions. I am considering it all. Since the leak is not between flanges, flange sealant is not appropriate. I would have liked to get an oversized stud plus some sealant but I could never find any. I strongly considered and even bought Permatex thread sealant, but Mahlon, who I trust, recommended Loctite Red 271. Regardless, the evil deed was accomplished last night prior to the start of Game 6 of the World Series. Go Cubs! Anyway, the stud is reinstalled with 271 and we'll put the governor on in the next couple of evenings and do a leak test. I will report back. I really do appreciate the opinions and thoughts. That's how I learn. I take none of it at face value, and think it through for myself and then accept and live with and overcome the consequences.

On the advice of the famous "Mahlon" of the Lycoming forum on Matronics and formerly of Lycoming, I have decided to use 271 Threadlocker Red. I will let you know how it comes out.

I don't think there is 600 psi. If there was the flat gaskets would not hold it. From studying up on this it appears the governor used engine oil pressure and regulates that to the prop. There is no oil pump in the governor, just flyweights and orifices that line up more or less to raise or lower pressure to the engine. Thanks, John

Ron, great idea. We are going to redo the stud with Locktite 271 tonight or in the morning. We will look for a crack in that are. Thank you for bringing this up. John

The stud was not very tight. Where can I find oversized studs? I think a closer fit would be great so the Locktite does not have to work as hard.

Thanks. I will check out PRC 1422 A.

I already have the plate installed. It goes on all dual mag Lycomings not just D suffix engines on Mooneys. See my earlier post where I put Lycoming SI 1438A and the Mooney document. The plate is not the problem. It is in place with two gaskets. Even the Mooney document which I also uploaded references Lycoming SI1438A. Lets go back to the key question for me. What sealant should I use on the stud that has oil leaking along it's length? Right now I am planning on using Permatex High Temp sealant. And I have not been able to find an oversized diameter stud as someone suggested earlier. If someone knows a source please post it.

I just caught this. We think The oil is leaking along the length of the stud, not around it's circumference.

A donation was just made. I will get to the avatar when I get time. Can someone share a link to the intake bolt leaking along it's length (thread). piloto, if your engine is a dual mag engine please see Lyc SI 1438a. There should be an .040 plate between the mounting pad and the governor. On the mounting pad side you use a Lyc gasket. The SI has the number. On the governor side you use the proper gasket for your governor. Mine is a Hartzell that does not look like yours. I have uploaded the SI along with a Mooney document about the problem. M20-120.pdf Lyc SI-1438A Propeller Governor Pad Plate PN LW-12347.pdf

Jose, you do have the Lycoming required spacer plate in place? If you have dual mags you need two gaskets and an .040 spacer between teh governor mount and the governor. Just checking. Some people have neglected to install the plate and that can cause catastrophic oil loss, a destroyed engine and possible bad outcome upon landing. John