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  #11  
Old 01-17-2021, 11:52 AM
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avrojockey avrojockey is offline
 
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Quote:
Originally Posted by lr172 View Post
Through stud is supposed to be a tight slip fit fit with the case bore. Most shops, like Divco, won't let the case out with bolts that do not meet that spec. This type of fit should not allow any significant oil passage. Further, o-rings are used inside the case surrounding these studs to avoid exactly this problem. How many hours on this engine? Loctite on the threads of the nut will do nothing. Would need to remove the jug and put some kind of sealant where the bolts leaves the case, if it is actually coming out via clearance at the stud.

If it truly is coming from the through studs, I would be worried about significant case fretting or a case crack at the webbing. Either way, it needs a professional examination.
About 1300 on a field overhaul that was thorough and extensively documented. almost 700 since topped with new ECI jugs....engine is running very good with clean oil so I would hate to jump to any conclusions.

Wouldn't fretting show up in oil analysis? Screen and filter have been clean, and AL is 5 ppm which is the universal average. Also, wouldn't fretting cause seeping at case split? I don't think anything is coming from there...either on top or bottom. Or, is it fretting between the through bolt and case?
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Last edited by avrojockey : 01-17-2021 at 12:16 PM.
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  #12  
Old 01-18-2021, 09:08 AM
lr172 lr172 is offline
 
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Originally Posted by avrojockey View Post
About 1300 on a field overhaul that was thorough and extensively documented. almost 700 since topped with new ECI jugs....engine is running very good with clean oil so I would hate to jump to any conclusions.

Wouldn't fretting show up in oil analysis? Screen and filter have been clean, and AL is 5 ppm which is the universal average. Also, wouldn't fretting cause seeping at case split? I don't think anything is coming from there...either on top or bottom. Or, is it fretting between the through bolt and case?
The case fretting does not produce a lot of metal and I doubt it would show up. The only exposure that the studs have to oil is where the case halves come together at the split line. I think that some older cases didn't have orings, but shops would machine a channel for orings in that spot to elimnate oil migration when the case was in for re-work. I believe it is common for wear here and oversize through studs are used. My 540 had 4000 hours and Divco had to put in all new studs when the case was overhauled to met the clearance spec.

Was your case sent in during the overhaul? If so, they typically machine down the case to address the fretting. If orings are not used on the through studs, case fretting would allow oil to migrate into the stud clearance area, if present, and work out the case end. This is getting to an area where you need some expertise to determine how concerned you should be.


Larry
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Last edited by lr172 : 01-18-2021 at 09:11 AM.
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  #13  
Old 01-18-2021, 07:55 PM
georgedouglas georgedouglas is offline
 
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Originally Posted by avrojockey View Post
Pun intended...things were getting too oily so I decided to hunt it down. Here's what I did...
  1. I washed down my O320-E2D really well with Aviation Simple Green and low pressure warm water to get most of oil and grime off.
  2. Finished wiping off any residue really well with avgas and shop paper towels
  3. Inspected engine under UV prior to running to ensure no oil was detected and engine was clean
  4. Ran engine for 5 minutes
  5. Inspected in dark hanger with UV flashlight

I possibly have a drainback tube leaking but I certainly have a cylinder stud or two leaking. Below is a picture of the worst offender. This is only after running for 5 minutes with a normal run-up.

You can see that the oil glows much better than I was expecting. I had read the Aeroshell glows under UV, but the this is Phillips XC without any dye added. In case someone wants to duplicate my process.

Im wondering what the best way to try and seal this up without pulling a jug??? Loctite 290 or low strength 220??? Permatex Spray Sealant
Tim, your studs are not the problem. Oil leaks are very hard to find on aircraft engines unless you examine it while it is running and then you may not find the source due to all the air swirling around. I went through this problem on my 0-320 B1A in my RV9A. I swore it was a leaking stud due to a bad "O" ring inside the case. I eventually tore the engine apart and did a field overhaul. I sent the cases to DIVCO and they found a crack in the case. That was the problem, no more oil leaks.
george
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  #14  
Old 01-19-2021, 06:57 AM
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Jeff Vaughan Jeff Vaughan is offline
 
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Default Green Loctite

I had a similar leak on my 0-360 Actually two of them. Applied green loctite which is the wicking type. One leak solved the other greatly reduced.
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  #15  
Old 01-20-2021, 12:44 PM
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avrojockey avrojockey is offline
 
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Originally Posted by lr172 View Post
Was your case sent in during the overhaul? If so, they typically machine down the case to address the fretting. If orings are not used on the through studs, case fretting would allow oil to migrate into the stud clearance area, if present, and work out the case end. This is getting to an area where you need some expertise to determine how concerned you should be.


Larry
Thanks Larry...starting to understand now how oil can be migrating that way. On further review of record, the case was not sent out but locally cleaned, inspected dimensionally (I have all those dimensions - journals, clearances, bore alignments, etc) and NDT with dye penetrant, alodined and painted. The only things sent out (Aircraft Specialties, Tulsa) for inspection were major steel parts...crank, cam, tappets, all hardware, and accessory case gears and shafts. The cam and some tappets were later rejected and replaced.

There is no record of case being reworked for o-rings, and this is the only recorded overhaul of this case in 1993.

A case crack would make total sense but with fretting this is what I'm trying to understand..if fretting is the cause of this leak on a properly torqued case, then why would cases be modified to have a o-ring in the first place? Seems that is just putting a band-aid on the situation much as added Loctite 290 would be.

Thanks for all the help...Who would you recommend as far a professional advise, other than the A&P that does my condition inspection? Is there a particular engine shop I can talk to?
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  #16  
Old 01-21-2021, 09:08 AM
lr172 lr172 is offline
 
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Originally Posted by avrojockey View Post
Thanks Larry...starting to understand now how oil can be migrating that way. On further review of record, the case was not sent out but locally cleaned, inspected dimensionally (I have all those dimensions - journals, clearances, bore alignments, etc) and NDT with dye penetrant, alodined and painted. The only things sent out (Aircraft Specialties, Tulsa) for inspection were major steel parts...crank, cam, tappets, all hardware, and accessory case gears and shafts. The cam and some tappets were later rejected and replaced.

There is no record of case being reworked for o-rings, and this is the only recorded overhaul of this case in 1993.

A case crack would make total sense but with fretting this is what I'm trying to understand..if fretting is the cause of this leak on a properly torqued case, then why would cases be modified to have a o-ring in the first place? Seems that is just putting a band-aid on the situation much as added Loctite 290 would be.

Thanks for all the help...Who would you recommend as far a professional advise, other than the A&P that does my condition inspection? Is there a particular engine shop I can talk to?
I would call Divco. They are the experts and likely to provide some guidance. I am not sure if case fretting or stud / bore wear could cause a leak here, but guessing they can if no oring is installed and I am just not sure if they are used on all or some cases. I would not expect fretting or bore wear to cause leakage if o-rings are used (no way for the oil to get out). I am pretty sure that I read that the o-rings channels are not universal, but shops like Divco will put them in when they re-work a case. I just can't recall the details; It may have been the locking sleeves that I am thinking of that help to prevent fretting and not o-rings. A bad o-ring certainly could cause leakage, but doubt they would go bad, even in 20 years. My big concern here is a case crack, that definately could cause this if the crack lead to the stud bore and expect many web cracks would, as that is one of the weak points in the web. Divco can share their experiences in this regard.

If you confirm that you have o-rings, I would be thinking case crack as the culprit.

Before going down this path, I would be absolutely sure that is where the oil is originating. If that is where it is coming from, DO NOT address this with loctite or other sealant, as a pretty likely cause is a significant case crack and that is not a problem you want to just cover up with sealant, at least not without expert guidance. That being said, the case can go a long time with some types of cracks. Divco told me it is not common to get a 540 case in for re-work that does not have at least one crack in the webbing. However, not all webbing cracks are equal when it comes to structural integrity.
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Last edited by lr172 : 01-21-2021 at 09:26 AM.
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  #17  
Old 01-31-2021, 06:06 PM
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It is definitely coming from the thru stud at the 1-1:30 position on the #2 cylinder. I cleaned everything up again until you could eat of it and inspected all around with a mirror...definitely the stud.

So I'm going to give Divco a call and ask for advise. I can only assume that removing that cylinder and through stud to inspect and possible do the Lycoming SI for oversized studs.

From my research and understanding...there's only 2 possible sources of oil: the case split where the interference fit on the stud is, or a crack in the webbing that joins high pressure gallery oil to the thru stud cavity.

Anyone else have insight?
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  #18  
Old 02-01-2021, 08:15 AM
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Talked to Divco...they seem to think that if it's leaking that much then the middle main is fretted.

They indicated that a crack will weep and then stain because a crack can go on in that area for a long time. I have more than a weep and it coming directly from the threads, so he said thats middle main fretting.
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Last edited by avrojockey : 02-01-2021 at 08:35 AM.
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  #19  
Old 02-02-2021, 05:49 AM
lr172 lr172 is offline
 
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Originally Posted by avrojockey View Post
Talked to Divco...they seem to think that if it's leaking that much then the middle main is fretted.

They indicated that a crack will weep and then stain because a crack can go on in that area for a long time. I have more than a weep and it coming directly from the threads, so he said thats middle main fretting.
Glad you came to a conclusion. I think this is one of the down sides of a field overhaul. If the case is sent to divco or other shop at o/h, they machine of a few thou off the case parting seam and then line bore it. This eliminates all the previous fretting wear and restarts the clock. If this i not done, that wear piles up over time and it starts fretting again from day 1 after overhaul, as the seam is not tight.

Larry
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