Oil sump gasket weeping

[Joe Larussa]

Anyone out there ever replace your oil sump gasket? Mine has a minor weep that’s bugging me. Looks like a lot of work.

[Vance Harral]

Our oil sump has been seeping for over a decade, and we've never done anything about it.  It does indeed "look" like a lot of work to do so, which is why we've never seriously investigated doing it.  But I don't know what's actually entailed.  My assumption is that it can't be done without removing the lower cowl and all of the intake and exhaust system, but perhaps there are clever tricks.

[laytonl]

3 hours ago, Joe Larussa said:

Anyone out there ever replace your oil sump gasket? Mine has a minor weep that’s bugging me. Looks like a lot of work.

I did that many years ago on my previous Mooney and it was a lot of work.  I remember there was something odd about how the pan interfaces with the accessory case.  When I bought my current Mooney (‘92 J), I noticed that someone had smeared PRC along the seam/gasket line on the old sump.  My sump doesn’t leak.  Lee

[Joe Larussa]

5 minutes ago, laytonl said:

I did that many years ago on my previous Mooney and it was a lot of work.  I remember there was something odd about how the pan interfaces with the accessory case.  When I bought my current Mooney (‘92 J), I noticed that someone had smeared PRC along the seam/gasket line on the old sump.  My sump doesn’t leak.  Lee

That’s where mine is leaking. So you’re saying the sealant thing works?

[cliffy]

Double check the torque on each sump to case bolt. Sometimes they loosen up. My top crankcase bolts did just that. A recheck on torque and the seep went away, Do not overtighten them just to try and get the seep stopped. 

Lots of case seeping in years past was done by cleaning with lacquer thinner (todays equivalent is brake clean in an aerosol can) and smearing on PRC just like the tank sealer.  Its not in the book but just sayin' it was done back when.  If its a bolt hole leaking then one would have to cover the entire bolt head and nut

You could clean it well with brake cleaner and spray the edges of the sump with foot powder  - run the engine for a short while and find exactly where it is leaking. 

[laytonl]

I didn’t put the PRC on mine.  A previous owner did it.  All I know is mine is not leaking.  Like Cliffy said others have done this too.  Lee

[Andy95W]

It may not be PRC, it could be this, which is also grey:

https://skygeek.com/la-co-11475-oylite-stik-1-1-4-oz-stick-8030-00-935-5841.html

Edited September 10, 2022 by Andy95W

[BDPetersen]

Yikes. I just posted my experience trying to find an oil leak and pulling the engine to find that the sump gasket was oozing with little physical evidence. Withe the engine out, removing the sump was easy enough. I never decided if the job could be done with the engine in situ, but I suppose there may be a way with patience. I wish you luck. You’re ahead of the game knowing exactly what your problem is. My leak was from a compromised gasket where the accessory case mates with the sump. I suppose if that were known to be the problem the accessory case could be removed and resealed, but that would be a gamble. It’s nice to no longer have oil puddles next to the nose wheel.

[BDPetersen]

In my case the accessory case interface with the sump had been sealed with the “red stuff”. The ooze suddenly got much worse which I attribute to the sump pad heater becoming partially detached causing it to overheat and soften the sealant.

[PT20J]

I’m currently taking a Lycoming maintenance class in Williamsport. The instructor told us a trick for field repair of seam leaks. This is for leaks at the crankcase parting line, but might be worth a try on the sump or accessory case.

Clean the area of the leak thoroughly with solvent. Then, plug the breather line and and connect a vacuum pump to the oil filler tube. Then, apply 290 green wicking Loctite to the affected area. The vacuum pulls the Loctite into the affected area (hopefully) sealing it.

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[EricJ]

19 minutes ago, PT20J said:

I’m currently taking a Lycoming maintenance class in Williamsport. The instructor told us a trick for field repair of seam leaks. This is for leaks at the crankcase parting line, but might be worth a try on the sump or accessory case.

Clean the area of the leak thoroughly with solvent. Then, plug the breather line and and connect a vacuum pump to the oil filler tube. Then, apply 290 green wicking Loctite to the affected area. The vacuum pulls the Loctite into the affected area (hopefully) sealing it.

Skip

And keep your fingers crossed that you're not the guy that has to split the case.   

[PT20J]

15 minutes ago, EricJ said:

And keep your fingers crossed that you're not the guy that has to split the case.   

Well, hopefully it’s a single, small section that’s leaking. I certainly wouldn’t do it on the whole seam.

The factory splits the cases with an automotive dent puller with a threaded adapter to match the large cylinder studs, and wooden wedges. 

[N201MKTurbo]

11 minutes ago, PT20J said:

Well, hopefully it’s a single, small section that’s leaking. I certainly wouldn’t do it on the whole seam.

The factory splits the cases with an automotive dent puller with a threaded adapter to match the large cylinder studs, and wooden wedges. 

Huh, I just pull out the through bolts and it comes right apart.

[PT20J]

26 minutes ago, N201MKTurbo said:

Huh, I just pull out the through bolts and it comes right apart.

Interesting. We took 5 engines apart in class today. These are engines that get taken apart and put back together every few weeks. None of them would part without some encouragement. 

[EricJ]

2 minutes ago, PT20J said:

Interesting. We took 5 engines apart in class today. These are engines that get taken apart and put back together every few weeks. None of them would part without some encouragement. 

Rich is just lucky that way, I think. 

In A&P school we had a case-splitting tool that would slowly push cylinder torque plates apart as you cranked on it.  Careful use of a rubber mallet or dead blow would help get the seams to release.   It worked really well, and the cases I used it on needed it.    I wouldn't want to have to do it with the added burden of loctite trying to hold it together, but that's just me.

The joke with the green loctite is that it locks the thing you think you're locking and everything else within a pretty long striking distance.   It has strong capillary action and can definitely go well beyond where you intend it to.   I think the advice to pull a small vacuum may not be just to draw it in the seam as it'll go way in there whether you want it to or not if that's where you put it, but if you draw a vacuum you *might* stand a chance of it not also locking all of the case fasteners along the seam where you applied it.   < only half-joking.

And it's a strong lock, and it needs heat significantly higher than the engine operating temps to release it, so it's a real pain to get it to let go.   I'd be reluctant to use it on an aluminum case where you really don't want it to distort from high localized heat application.

I wonder if the guy that suggested that ever had to deal with the consequences. 

[Guest]

The thru studs are normally an interference fit in the case, this keeps the oil from running down the studs and leaking out at the cylinder flange.

[PT20J]

14 minutes ago, EricJ said:

I wonder if the guy that suggested that ever had to deal with the consequences. 

Good question; I don’t know. I’ll ask tomorrow.

He is an old timer IA and was a Lycoming tech rep for years and now teaches A&P courses at Pennsylvania College of Technology which Lycoming has contracted to teach the factory maintenance course I’m taking. 

One thing to consider is that some adhesives are stronger in shear than tension, or vice versa. I assume Loctite is strong in shear given it’s intended application as a thread locker, but I have no idea of its tensile strength. I do know superglue, while very strong in tension, had almost no shear strength. 

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[EricJ]

20 minutes ago, PT20J said:

Good question; I don’t know. I’ll ask tomorrow.

Let us know what you find out!    I'd be really reluctant to try that on first blush.

 

[N201MKTurbo]

2 hours ago, PT20J said:

Interesting. We took 5 engines apart in class today. These are engines that get taken apart and put back together every few weeks. None of them would part without some encouragement. 

Oh, alright, I may have given it a few taps with a rubber mallet. 

[PT20J]

I asked the instructor, Mike Damiani, about it. He said he had never personally split a case that had had green Loctite applied. He said it was actually a procedure developed by Continental, so perhaps Continental has a document describing it. 

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