Oil leak on governor mounting stud

[Bubblehead]

I have an O-360-A1F6D engine on my RV-8.  I know that is not a Mooney but I have learned a lot from reading this forum, and this engine is used on Mooneys so I hope I am not violating any rules.

In early summer the engine developed an oil leak. We finally narrowed the source down to the prop governor area and changed gaskets a couple of times but the leak continued.  We do have the Lycoming required spacer plate and correct gaskets.  This week I had the governor bench tested at Byam Propeller Service in Fort Worth, TX but the governor itself was not leaking.  BTW the people at Byam are fantastic.

 

My mechanic decided that maybe we had a leak along a stud and upon inspection found the lower outboard stud was a little loose, and when he removed the stud he found that the stud was not in a blind hole but was partly exposed to the oil in the accessory case and maybe in the flow of the oil return line!

 

We pulled the stud out and it was clean with no sealant of any kind.  Normally I would expect a stud to be put in with at least Loctite. Perhaps the sealant got carried away after all these years.  BTW the engine has 1000 hours SMOH but the prop governor has never, to my knowledge, been overhauled. 

 

1) Should the stud be open to the return flow and oil in the accessory case?  If not then I have an accessory case problem.

2) What sealant/thread lock should we install the stud with?

3) Have others had this problem, and if so, how did you eliminate the oil leak?

 

Remember this is a dual mag engine and the governor mounting pad is integral with the accessory case.  Non-dual mag engines have a separate adapter.  Attached is a picture of the governor mount.  The lower right hand stud is the one that seems to be leaking.

 

Thanks for the help.

[carusoam]

Welcome aboard, BH.

Stand by for someone with some actual knowledge.

There are some ways to best determine where the leak is coming from.  

As far as not flying a Mooney yet...

Consider sending a donation to the site.

Also update some avatar data when you get a chance.

Best regards,

-a-

[Bubblehead]

carusoam,

Thanks for the reply. I think we've got the leak identified.  I am mostly looking for background info on the stud and leaks on it and suggestion on show to seal it.

I did not say I am not flying a Mooney yet.  I have 300+ hours in 201s and 231s but don't own one.  They are great airplanes but the RV-8 suits my "mission profile" right now.

I will send a donation but could not find a place on the site to do that.  Please post directions or a link and I will do it today.  I'm not too concerned with my avatar data right now.  I am focused on fixing the leak and flying my plane.  

 

[Piloto]

Bubblehead

What a coincidence I am going to play lotto today.

I have exactly the same leak and just replaced the governor gasket yesterday. Ran the engine on the ground this morning and I can still feel oil with my fingers on the lower extending tube next to the lower stud. I set the prop to low RPM to force pressure into the line. To my surprise I found wet oil at the governor line nut just above the stud. The leak on the ground is not too bad but inflight it wets the whole belly. I guess because there is constant oil pressure to keep the prop from over speeding. Will try it this afternoon again.

Please keep me posted on your findings.

José

Edited October 29, 2016 by Piloto

[Bubblehead]

Piloto, it sounds like the same thing.  Lower prop RPM is higher pressure.  For a ground check without the cowl the prop shop said to get the oil warm, then RPM up to the cycle rpm, which is about 1900 rpm, and slowly lower the rpm's 100 or so and just sit like that to give it time to work.  After about 3 minutes I get one small drop.

If I fly with the current leak I lose about 1 qt every 2-3 hours and the belly gets coated.  I don't like flying like that but twice we've changed gaskets and twice I flew for an hour to test it out.  Disappointed both times.

Friday night I used some Permatex #2 on teh stud, reinstalled the stud, reinstalled the governor.  No leak for about 5 minutes.  I think the warm or hot oil gradually reduced the viscosity of the Permatex and ultimately found its way out along the stud again.  I have been Googling various things and reading all I can today but have not come across this anywhere else, and I don't find any references to the right thread lock/sealant to use.

Right now I think the way to go is a thread lock that fully cures instead of staying soft like the Permatex #2 does. Apply it to a clean stud, let it cure for the required time and then test it. A fully cured and hard thread lock/sealant won't lose strength when it gets hot and the oil won't be able to "flush" the sealant out.  I am off to the auto parts stores now to investigate products.

I hope we find someone on here that has had the problem and solved it.  Let's keep posting what we find.

[Bubblehead]

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

Edited October 29, 2016 by Bubblehead

[Guest]

7 hours ago, Bubblehead said:

I have an O-360-A1F6D engine on my RV-8.  I know that is not a Mooney but I have learned a lot from reading this forum, and this engine is used on Mooneys so I hope I am not violating any rules.

In early summer the engine developed an oil leak. We finally narrowed the source down to the prop governor area and changed gaskets a couple of times but the leak continued.  We do have the Lycoming required spacer plate and correct gaskets.  This week I had the governor bench tested at Byam Propeller Service in Fort Worth, TX but the governor itself was not leaking.  BTW the people at Byam are fantastic.

 

My mechanic decided that maybe we had a leak along a stud and upon inspection found the lower outboard stud was a little loose, and when he removed the stud he found that the stud was not in a blind hole but was partly exposed to the oil in the accessory case and maybe in the flow of the oil return line!

 

We pulled the stud out and it was clean with no sealant of any kind.  Normally I would expect a stud to be put in with at least Loctite. Perhaps the sealant got carried away after all these years.  BTW the engine has 1000 hours SMOH but the prop governor has never, to my knowledge, been overhauled. 

 

1) Should the stud be open to the return flow and oil in the accessory case?  If not then I have an accessory case problem.

2) What sealant/thread lock should we install the stud with?

3) Have others had this problem, and if so, how did you eliminate the oil leak?

 

Remember this is a dual mag engine and the governor mounting pad is integral with the accessory case.  Non-dual mag engines have a separate adapter.  Attached is a picture of the governor mount.  The lower right hand stud is the one that seems to be leaking.

 

Thanks for the help.

Once you find the stud part number, see if you can find one in an oversize, like plus 003". That should tighten it in the hole.

Clarence

[Piloto]

See attached picture of my governor. I replaced the original gasket with the screen that goes on the engine side. Where this 0.040" spacer goes?

I ran a test this afternoon setting the governor to low RPM from 1700 rpm to 1000 rpm after 7 minutes oil started coming on the windshield and right wing. It was a mess. I shut down immediately with oil pressure on the engine. I look for any obvious source of the leak but found nothing, everything on the back was wet. I found that the governor nuts were at least 1/4 turn loose. I know I had them tight before. All the oil hoses nuts were tight.

In your case I don't think the engine stud is the culprit since the gasket surrounds it completely. My engine looks exactly like yours

José

Edited October 30, 2016 by Piloto

[carusoam]

There are a couple of threads that are interestingly related...

One is the topic of Loctite and it's service temperature.  Another is an intake bolt that might be leaking down it's thread.

If you get some time...

1) the avatar updates help us help each other... plane, engine, home drome. That kind of thing...

2) the donations help keep this site alive...

No high pressure sales technique.  We strive to solve each other's aviation challenges from what we have learned ourselves...

Best regards,

-a-

[carusoam]

José,

Is it possible that grounding strap isn't allowing the bolt/nut to seal?  Possible scratched surfaces?

Best regards,

-a-

[Bubblehead]

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

Edited October 30, 2016 by Bubblehead

[Piloto]

7 minutes ago, carusoam said:

José,

Is it possible that grounding strap isn't allowing the bolt/nut to seal?  Possible scratched surfaces?

Best regards,

-a-

The ground strap terminal is just like another washer. My mechanic and I did a through check of the surfaces. I have no smoking gun of the leak source but a suspected area. All I can tell that is a pressure leak.

[carusoam]

The other thread was an intake bolt with an oil drip.... similar that the thread might be allowing oil to run up the bolt...

higher the temperature, the lower the oil viscosity...

higher the pressure, the higher the driving force for oil to be pressed out...

And thanks for the site donation.  That is always appreciated!

Best regards,

-a-

[Piloto]

Bubblehead

I think you nailed down my problem. My engine was overhauled in 2007 but the spacer and added gasket were not installed. I am ordering the gasket/spacer set on Monday.

Thanks a lot for the advice. Will keep you posted.

José

[Bubblehead]

7 hours ago, Piloto said:

In your case I don't think the engine stud is the culprit since the gasket surrounds it completely. My engine looks exactly like yours

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

[Guest]

Here is Mooney SI M20-120 it covers the correct installation of propeller governors on D suffix engines.

http://mooney.com/en/si/M20-120.pdf

Clarence

[Piloto]

Bubblehead

Here is a picture of my governor mounting pad and the governor. Even though the SI M20-120 is for Mooneys only I think it will applicable for your plane too.

José

[Bubblehead]

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.

[Piloto]

15 minutes ago, Bubblehead said:

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.

For oil and gas sealing I use PRC 1422 A. I have used it on the push rods shroud tubing and crankcase split perimeter. It holds very well. Before applying clean the surface very well with MEK.

[Bubblehead]

Thanks.  I will check out PRC 1422 A.

[Marcopolo]

  The actual original question was if that particular stud hole should be blind or if it should be open to the return oil in the accessory case.  Is it possible that the stud in that position was over tightened thus cracking the base of the hole and creationg this leak?  The fix may still be the same but the origin of the leak and how many it affects would change based on this answer.

 

Ron

[N601RX]

The op mentioned the stud was removed and reinstalled. How tight was it when putting back in?  Lycoming has a min driving torque for most is their studs. Also .001, .003 and possibly .006 oversized studs are available. The stud will be looser at temp than at ambient. 

[Piloto]

I still don't see how the stud could be the culprit of the leak. The stud is at the lowest point were oil would accumulate from an actual leak source above.

José

[Marcopolo]

Jose,

The OP mentioned that this particular stud does not go into a blind hole but rather backs up to an oil return into the accessory case, this is where his oil leak is coming from (according to the OP).

[Bubblehead]

3 hours ago, N601RX said:

The op mentioned the stud was removed and reinstalled. How tight was it when putting back in?  Lycoming has a min driving torque for most is their studs. Also .001, .003 and possibly .006 oversized studs are available. The stud will be looser at temp than at ambient. 

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.