Cyllinder base oil leak, repair or defer?

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farmrjohn

Pre-takeoff checklist
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farmrjohn
After a 3 hour cross country flight I noticed some oil streaking from the cowl and along the fuselage. I wiped that down, inspected the engine, and the base of the #4 cylinder exhaust pushrod tube had a drop of oil on it, as well as some general oiliness inside the engine compartment on the left side. I wiped all of that down, flew for .8 hrs. and noticed more light oil streaks and another drop on the base of the pushrod tube. My mechanic took a look and said the oil appears to be coming from the base of the cylinder, most likely from the O-ring, and to repair would require pulling the cylinder to the tune of 6-8 hours of labor, plus parts. He said it wasn't an airworthiness issue and said as long as I didn't mind the wiping down there was no immediate need for repair. Engine is a mid to high time O-200A. Is this something that can wait until the next annual (Feb '19) or overhaul or should it be addressed now? I've seen comments on causing more problems due to changing torques and the status quo when attempting partial corrections.
 
farmrjohn said:
After a 3 hour cross country flight I noticed some oil streaking from the cowl and along the fuselage. I wiped that down, inspected the engine, and the base of the #4 cylinder exhaust pushrod tube had a drop of oil on it, as well as some general oiliness inside the engine compartment on the left side. I wiped all of that down, flew for .8 hrs. and noticed more light oil streaks and another drop on the base of the pushrod tube. My mechanic took a look and said the oil appears to be coming from the base of the cylinder, most likely from the O-ring, and to repair would require pulling the cylinder to the tune of 6-8 hours of labor, plus parts. He said it wasn't an airworthiness issue and said as long as I didn't mind the wiping down there was no immediate need for repair. Engine is a mid to high time O-200A. Is this something that can wait until the next annual (Feb '19) or overhaul or should it be addressed now? I've seen comments on causing more problems due to changing torques and the status quo when attempting partial corrections.
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OMG your mechanic is a freaking idiot, Doesn't he/she know the cylinders are held on by thru case bolts? The only ways for a cylinder base to leak is for a cylinder hold down stud or a cylinder thru case bolt to be loose. the only way they get loose is to stretch them. How do you stretch them? detonation!
GET that engine off of there and get it rebuilt, before it kills you.
 
I have an O-360.... and several pushrods are weeping at the case.... I do not see the value in pulling cylinders to replace the gaskets on the pushrods when so much can happen after pulling the cylinders.... I'm firmly in the "if it ain't broke, don't fix it" camp. sometime we cause more problems trying to make something "perfect" that works very well just the way it is.

So a cylinder base that is leaking needs to be looked at before next run... pushrod?, clean it off and keep an eye on it.
 
Pushrod tube seal leaks are pretty common in Lycomings. A tipoff is if the seals are hard as a rock. If a bad seal is is cause of your leak, it is relatively easy to fix.
 
For my education, what are you seeing?
I once opened my cowl after the KY fly in and saw this bit of oil on my 0-320
Mx said wipe it off. It has been 4 months and has never come back.
Clean bill of health at annual so not sure what it was.
Made me nervous.

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What Tom said!

Mine looks like that and will get oily at times. My mechanic says meh no big deal. Anti corrosion program I suppose. I've seen planes leave all kinds of puddles on the ground and nobody bats an eye. If that is the only leak I wouldn't worry. And bring me back to my Air Force days.." is it in excess of 3 drops per minute ?". Well no it's not, well it ain't a leak then. Boom!

To the OP, oil tends to run down not up so if you have oil on your push rod tube AND down below it I would suspect your leak is the push rod tube seal. I'm no A&P so take it for what it's worth.
 
Glenn D said:
I have an O-360.... and several pushrods are weeping at the case.... I do not see the value in pulling cylinders to replace the gaskets on the pushrods when so much can happen after pulling the cylinders.... I'm firmly in the "if it ain't broke, don't fix it" camp. sometime we cause more problems trying to make something "perfect" that works very well just the way it is.

So a cylinder base that is leaking needs to be looked at before next run... pushrod?, clean it off and keep an eye on it.
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A Lycoming O-360 doesn't need the cylinders pulled off to change pushrod tube seals. Small Continentals are another animal entirely. They use small rubber boots on the case end of the pushrod tube, and the cylinder has to come off to replace them. You replace the cylinder base seal at the same time. Those boots can work their way off their nipple and up the tube, and a LOT of oil gets out. You could run out of oil if enough of them came loose.

Oil all over the engine compartment is not good. It gets into mags and the alternator or generator and the vacuum pump drive's coupling and causes problems. It gets into the cabin heat muff and can send smoke into the cabin. It can catch fire if it gets hot enough. It drips on the nosewheel tire and does the rubber no good.
 
Glenn D said:
I have an O-360....
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Your engine has a totally different concept for push rod tubes, yours are nor swaged in on one end to the cylinder, the 0-200 only has seals on one end of the pushrod tube. You can remove you pushrod tube and re-seal it.

But if it were your case center seam leaking you would have the same problem as the OP.
 
bnt83 said:
An O-200A with an oil leak? Say it ain’t so... Some pretty extreme advice in here if you ask me.
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Cylinder base oil leak, pretty serious, the only way you get one there is a loose cylinder.
 
Tom-D said:
Cylinder base oil leak, pretty serious, the only way you get one there is a loose cylinder.
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how loose you talking for reference? Can put a big wrench on it and get a turn on the nut type of loose, can physically move the cylinder, or loose but you just never know other than seepage of oil and everything appears normal?
 
simtech said:
how loose you talking for reference? Can put a big wrench on it and get a turn on the nut type of loose, can physically move the cylinder, or loose but you just never know other than seepage of oil and everything appears normal?
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Let's put a different way, the 3/8 inch get torqued to 275-325 Inch pounds, on the small studs, and the thru bolt and 7/16" get torqued to 400 to 450 inch pounds.
You would be required to loose the torque to leak.
Would you fly an engine with a loose cylinder?
If it is really leaking at the cylinder base, that cylinder AND the CASE is loose.

this is what I do.
 

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so how much oil is leaking.....per hour? if it uses less than 1 quart in 7 hrs, I'd not worry and just clean and keep an eye on it.
 
I'm not familiar with Continentals, but is there an o-ring to seal the cylinder/case joint? If so, could you have a failing o-ring and an imperfect mating surface between the cylinder and case?
 
kyleb said:
I'm not familiar with Continentals, but is there an o-ring to seal the cylinder/case joint? If so, could you have a failing o-ring and an imperfect mating surface between the cylinder and case?
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Yes there is a o-ring, it is trapped between the cylinder base and the case. It is placed on the cylinder skirt, and squished as the cylinder is tightened.
 
Checkout_my_Six said:
so how much oil is leaking.....per hour? if it uses less than 1 quart in 7 hrs, I'd not worry and just clean and keep an eye on it.
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Leave it to you to try and get someone killed for humor.
 
Why would you not have it fixed when you first find out about it? Have you ever seen an oil leak get better on it's own?
 
Tom-D said:
Let's put a different way, the 3/8 inch get torqued to 275-325 Inch pounds, on the small studs, and the thru bolt and 7/16" get torqued to 400 to 450 inch pounds.
You would be required to loose the torque to leak.
Would you fly an engine with a loose cylinder?
If it is really leaking at the cylinder base, that cylinder AND the CASE is loose.

this is what I do.
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What is the black goop on the parting surfaces.
 
SixPapaCharlie said:
For my education, what are you seeing?
I once opened my cowl after the KY fly in and saw this bit of oil on my 0-320
Mx said wipe it off. It has been 4 months and has never come back.
Clean bill of health at annual so not sure what it was.
Made me nervous.

View attachment 66326
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Totalled - no saving that engine. You're going to die. Trust me, I'm an engineer.
 
JOhnH said:
Why would you not have it fixed when you first find out about it? Have you ever seen an oil leak get better on it's own?
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Sometimes and likely most of the time when we try to fix a small leak we make it worse or create another problem. Most leaks are nothing to worry about, some obviously can have serious consequences so to me it's about what battle to fight.

And yeah I've seen oil leaks get better on their own...its when a piece of trash in the oil finds the leak and plugs it. No joke...in a ground based vehicle of course. Hahaha
 
I hate oil leaks. For gaskets the first response is to use Real gaskets and pushrod tube seals. That solves most problems. Not using a semi-synthetic multi weight oil will also help, if you’re using one. That stuff will seep out where mineral oils won’t. There is a mineral oil multi weight available.

Charlie, are you a fan of silk thread at case mating surfaces? I know that’s going away with new sealants. My mechanic had me use Hylomar and silk. It worked perfectly so no complaints.
 
I remember the guys that worked on these said if it's not leaking oil it was out of oil...:rolleyes:
 
AKBill said:
I remember the guys that worked on these said if it's not leaking oil it was out of oil...:rolleyes:
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P&W 2800 has a great many more seams than the 0-200, plus the "buck 18s" were worn out by the time anyone here ever saw them.
 
Stewartb said:
I hate oil leaks. For gaskets the first response is to use Real gaskets and pushrod tube seals. That solves most problems. Not using a semi-synthetic multi weight oil will also help, if you’re using one. That stuff will seep out where mineral oils won’t. There is a mineral oil multi weight available.

Charlie, are you a fan of silk thread at case mating surfaces? I know that’s going away with new sealants. My mechanic had me use Hylomar and silk. It worked perfectly so no complaints.
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I don't know if Charley is or not, But there are several products on the market now that replace thread very well. The Hylomar is one, a thinned coat of # 2 permatex is another.
Chuck Ney (MHRIP) once told me that machine shops pay great attention to get all the bearing and case clearances perfect, then why stick something in there to prevent the seam from coming together properly?
Kinda made sense when said it.
 
Tom-D said:
P&W 2800 has a great many more seams than the 0-200, plus the "buck 18s" were worn out by the time anyone here ever saw them.
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I was in VP-90 from 1984 to 1995 working on P-3's and VR-51 flew the C-118 I believe. Don't remember when VR-51 was decommissioned..
 
kyleb said:
I'm not familiar with Continentals, but is there an o-ring to seal the cylinder/case joint? If so, could you have a failing o-ring and an imperfect mating surface between the cylinder and case?
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Yup. That's the usual problem. Aging seals.
 
Oil Leaks- Some humor in this thread. Reminds me of the time when I was in the back seat of an SH-2G helicopter flying from MD to Kaman in CT after a week of flight testing with the Navy. The main gear box was leaking heavily and the oil was streaming down the side of the helicopter so I informed the test pilot. We kept flying and the pilot told me to let him know when the oil stopped flowing! We made it to CT without an issue other than a huge mess on the outside. This test pilot had witnessed this main gear box design being stress tested on the ground rig with no oil and was very confident in the design.
 
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are you a fan of silk thread at case mating surfaces? I know that’s going away with new sealants.
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I like the idea but how does one get around the apparent requirement in M-0 (3-3.1.1. Four Cylinder Engine Crankcase Threading) to use PN 646942 (gasket maker) and CMI PN 654663 (Loctite 30516 gasket sealant with PN 641543 Silk Thread)?
 
Let'sgoflying! said:
I like the idea but how does one get around the apparent requirement in M-0 (3-3.1.1. Four Cylinder Engine Crankcase Threading) to use PN 646942 (gasket maker) and CMI PN 654663 (Loctite 30516 gasket sealant with PN 641543 Silk Thread)?
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or other methods, techniques, and practices acceptable to the Administrator,
 
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