Tips On Troubleshooting Oil Leak

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Brad
Post is a bit long

For the past 15 flights or so the 182 has been running at an oil level just over 9qts which seems to be the sweet spot for not giving the belly a bath. The flight before last I noticed it had dropped a bit so I added 1qt this morning. I had also noticed a few drops on the pavement on that previous flight and again today after taxiing up the hangar. When I pulled the plane into the hangar I have a drip pan and noticed several fresh large drips as there was some fuel from when I previously pulled the fuel sump on the belly. That fuel really magnified the drops...a good thing! Hmmm???? So I crawled under and it had this new layer of oil like it had almost went directly from my newly added quart (before the flight) directly onto the belly.

So I walked the plane and noticed a bit on the co-pilot side exterior just in front of the door about at waist level that streamed out between the upper and lower cowling seem. So I pulled the top cowling. Yep...thin film of oil all over the place. The entire top of the strut was filled with engine oil (not strut oil) like a mini reservoir. So at a minimum it had pooled there if not directly dripped down into that location. There was light film over a lot of the firewall and along various components. I inspected the inside of the top cowling and there wasn't a spec of oil forward of the baffling. Behind the baffling you could see it had misted or sprayed up there.

Needless to say, not gonna fly it. However, I was wondering if anyone has any good tips on how to ground run it and localize the leak? I am comfortable removing / re-installing the lower cowling. I plan to wipe it all down really good after it finally cools off. I will take one last look to see if I can see any hint of the actual source.

My goal was to run it up after cleaning everything. To be safe seems like all I can really do is run it a bit, shut it down a look to see where it is from. That prop just seems too close to where I would have to stand to catch it while idling/running.

So I probably lost 3/4 of quart and maybe as much as 1 quart in about 1.2hrs logged. It is definitely not the strut. No hard landings or porpoising. There is no apparent leak any where around the filler. The filler cap was on tight and lanyard was on. The dipstick was in place. The quick drain valve seems to be forward of he leak and no oil anywhere near it. I can't see any oil up top forward of the rear baffling. But I do see some oil pooled on top of the air inlet duct to the carb. The oil strainer safety wire was still in place but it was too hot to touch to see if it was somehow loose. There was a small drip of oil under at the bottom of the oil strainer. But there was also a bit of oil under other fittings as well in equal amounts.

During the flight I never smelled oil. CHT, oil pressure and oil temp all seemed good. Maybe I could say the prop was a bit slow to cycle to during run-up in these really warm temps which isn't quite the norm. During flight it operated just fine. Zero oil made it to the windshield (thankfully).

It feels like the dipstick leaked or a fitting for oil pressure or oil temperature. The prop governor was removed and inspected last year so maybe that lead to a leak now? Not sure if this is a oil breather type failure.

Fuel burn was normal.

And probably not related but worth mention is that the engine starts have been like a low battery or like a bad connection. I have been keeping it on a tender. The start at OAT of 97F was slow. But today at 70F I expected it to crank right over and it was still like a dead battery so maybe just a battery problem.
 
Remove the cowl, inspect push rod tubes. That’s the most common leak location and usually an easy one to fix. Beware, pressure cowls spread the oil. Look for hanging drips on the tube springs.
 
Stewartb said:
Remove the cowl, inspect push rod tubes. That’s the most common leak location and usually an easy one to fix. Beware, pressure cowls spread the oil. Look for hanging drips on the tube springs.
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I agree with this 100%. Many times the push rod tube seal leaks on big continentals will be deceiving because they leak more oil than you think they should and it ends up everywhere.
 
I’d get everything spic and span...degreased well. Get two spray bottles. In one fill with kerosene the other denatured alcohol. Spray it down with kerosene then spray with compressed air then the alcohol then more compressed air. Get both engine cowling and firewall clean. Then button everything back up and ground run up. Come back and decowl it. It won’t be an oily mess but you will see the source of the leaks.

Don’t fly it and expect to find the source. There’s way too much air flow moving the oil around. You’d be surprised at how little oil it takes to make a mess. I doubt you're losing more than a half cup or less.
 
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Thanks guys...awesome advice. Not looking forward to the cleanup but hopefully that and a run up will reveal the problemo.

So the run up won't blast it all over the place again? I'm guessing just the prop wash into the cowl openings is no where near what the cruise airflow is like?

I'm gonna find a manual and make sure I know all the locations to look for...starting with the push rod tubes!
 
Do you have a spin-on oil filter adapter? Check and make sure the adapter is not loose. There should be torque putty between it and the case, just to visually check that it’s still tight. Simple to check, just in case.

Also make sure your dipstick is seated and tight against the case. If it’s loose or pulls out, it can both leak and show low on the dipstick. You should be able to assess that visually as well based on how far the dipstick handle is from the access door normally. Again, stupid simple to check and keep an eye on.
 
Inspect and find general area of leak. Look for drips towards the top of the engine. Clean engine down with whatever - I vote for mineral spirits/varsol. Spray isopropyl alcohol or something that readily evaporates to clean suspect area again and then dry again.

Spray NDT developer on suspect area, a thin coating. It dries to a white, chalky coating that will absorb and makes identifying the leak easier. Bon Ami in a spray can will also work.

I have used oven bags to cover a component in order to isolate a leak. They are made for heat. Oil in the bag = the component. Oil on the outside of the bag = keep looking.
 
mondtster said:
I agree with this 100%. Many times the push rod tube seal leaks on big continentals will be deceiving because they leak more oil than you think they should and it ends up everywhere.
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Yes, these commonly leak at the upper end and almost never leak at the crankcase end due to Continental's dumb design. So if you want to fix you can replace the upper seal for hundreds of dollars of labor and may still have a leak or you can use my 100% successful method for one hour or less labor and less than one dollar in parts. Big spenders please ignore.
 
Snowmass said:
Yes, these commonly leak at the upper end and almost never leak at the crankcase end due to Continental's dumb design. So if you want to fix you can replace the upper seal for hundreds of dollars of labor and may still have a leak or you can use my 100% successful method for one hour or less labor and less than one dollar in parts. Big spenders please ignore.
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Ok, I’ll nibble. What’s the method you use, if you’re willing to share?
 
Stoddard solvent through a syphon gun hooked to a compressor line is the right tool for cleaning my engine. Finish with a little acetone to leave things squeaky clean. The combo of solvent and compressed air works great.
 
455 Bravo Uniform said:
Do you have a spin-on oil filter adapter? Check and make sure the adapter is not loose. There should be torque putty between it and the case, just to visually check that it’s still tight. Simple to check, just in case.

Also make sure your dipstick is seated and tight against the case. If it’s loose or pulls out, it can both leak and show low on the dipstick. You should be able to assess that visually as well based on how far the dipstick handle is from the access door normally. Again, stupid simple to check and keep an eye on.
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No spin on adapter. Just the old strainer with safety wire.

The dipstick was locked in place. I'm weird that way, except fuel and sumping, checking out is the first thing I do and my last step is verify it is snapped in.

Now the strut level can really effect the dipstick level. Fortunately the strut is holding nicely so I trust the dipstick level. But it was so hot I didn't get a chance to see if its leaking where the dipstick tube goes into the motor.

I can't look or troubleshoot again until Saturday. Will check dipstick to see how much really leaked. But I am guessing I leaked more than half quart and possibly a full quart in that 1.2hrs logged. The starter or battery or ??? is resulting in it barely starting...like a bad connection. Now wondering if oil misted someplace around the starter too. The mag check was fine and had full power in that last fight. Not my favorite mystery.
 
I should have been more clear - dipstick tube, not the dipstick itself. Make sure it’s fully seated and tight. Mine was loose and giving me erratic readings until I noticed one day the the door was almost touching the dipstick handle and the dipstick was fully seated in the tube, but the tube was loose at the case.
 
Previous owner to the Cherokee couldn't find the source of my oil leak. Spent a day and a half cleaning the belly and a few hours cleaning the cowl. Used a dye kit. One trip in the pattern and clearly saw where it was. Oil pressure screen housing. Removed housing and saw it was cracked. Only it was cracked on the opposite side of where the oil seemed to be coming from. Looked at the gasket and you could see an indent in the gasket from the crack. They re-used a 2 dollar gasket! Lycoming wants 750 bucks new. Found one on eBay for 40.
 
455 Bravo Uniform said:
Ok, I’ll nibble. What’s the method you use, if you’re willing to share?
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I should probably just write this up but it's very simple.

Take of valve cover and using Q-tips completely and thoroughly clean out that channel between the upper valve tube seal washer and the cylinder head. Lacquer thinner for a final clean. Completely fill the channel with high temperature RTV silicon. Now oil will not even get to the seals to leak as the RTV has blocked it. Do both valves while your at it. When I majored my IO-520 I did this to begin with and no chance of a leak ever. It's even simpler before the rocker arms are installed. Also, if it's undamaged, you can use the old cover gasket by covering with a film of RTV so the total parts cost is pennies for the tiny amount of RTV.
 
Snowmass said:
I should probably just write this up but it's very simple.

Take of valve cover and using Q-tips completely and thoroughly clean out that channel between the upper valve tube seal washer and the cylinder head. Lacquer thinner for a final clean. Completely fill the channel with high temperature RTV silicon. Now oil will not even get to the seals to leak as the RTV has blocked it. Do both valves while your at it. When I majored my IO-520 I did this to begin with and no chance of a leak ever. It's even simpler before the rocker arms are installed. Also, if it's undamaged, you can use the old cover gasket by covering with a film of RTV so the total parts cost is pennies for the tiny amount of RTV.
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RTV has been known to break free and get into places it doesn't belong and cause engine failures. It has no business inside an engine. Nowhere in Continental's approved sealants list do we find any silicone. https://www.cocotier.org/engines/continental/Service Bulletins/SB_Continental/sil99-2.pdf
 
Snowmass said:
I should probably just write this up but it's very simple.

Take of valve cover and using Q-tips completely and thoroughly clean out that channel between the upper valve tube seal washer and the cylinder head. Lacquer thinner for a final clean. Completely fill the channel with high temperature RTV silicon. Now oil will not even get to the seals to leak as the RTV has blocked it. Do both valves while your at it. When I majored my IO-520 I did this to begin with and no chance of a leak ever. It's even simpler before the rocker arms are installed. Also, if it's undamaged, you can use the old cover gasket by covering with a film of RTV so the total parts cost is pennies for the tiny amount of RTV.
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This is why planes with owner performed maintenance in Canada aren't allowed back in the US.
 
JAWS said:
Now that is a misguided statement.

https://www.kitplanes.com/vans-aircraft-sued-for-35-million-over-rv-10-crash/

https://www.kitplanes.com/best-practices-sealants/
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Kind of validated my point. When you allow owners to do weird nonstandard things, that's exactly what happens. This is what I was referring to, and your links are exactly what the FAA wants to avoid. And why an airplane from Canada under the owner maintenance category is ineligible to be exported to the states. Someone accidentally sucking rtv into a fuel line because the previous owner doesn't know how fittings work. Not sure how that is misguided.

https://copanational.org/en/owner-maintenance/
 
I find a lot (A LOT!) of oil filler necks loose because pilots put way too much elbow into the dipstick. The dipstick should be just finger tight.

De-cowl the engine. Spray the **** out of it with mineral spirits. I mean really get in there. Warning: it'll create quite the cloud.

Then blow it off with shop air and make sure the engine is good and dry.

Run the engine for a few minutes, shut it down, and put it in a dim hangar.

Use a UV pen light and start from the back of the engine. Look for pooling around stud fasteners on the accessory case, oil filter adapter if applicable, etc.

I almost guarantee you'll find oil where the filler neck meets the case. Typically, I cut the safety wire, remove the neck, clean everything, replace the gasket, and reinstall.

Keep in mind, when the engine is fully cowled, the oil will work it's way forward as you fly.

Often, another culprit is the crankshaft seal. But that's usually pretty easy to spot. Not so fun to replace though.

Anyway, rather than spend all your June weekends looking for the problem, just take it to an A&P and let them handle it.
 
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Also, please don't put RTV at the end of your shroud tubes...for the love of God
 
If you really want to find the source the best method is florescent dye, shows up under UV flashlight. You don't even need to clean it up beforehand. No guessing, it will be obvious.
 
Racerx said:
Kind of validated my point. When you allow owners to do weird nonstandard things, that's exactly what happens. This is what I was referring to, and your links are exactly what the FAA wants to avoid. And why an airplane from Canada under the owner maintenance category is ineligible to be exported to the states. Someone accidentally sucking rtv into a fuel line because the previous owner doesn't know how fittings work. Not sure how that is misguided.

https://copanational.org/en/owner-maintenance/
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And my point is that the US already has owners doing all sorts of non-standard stuff. "Hangar Fairies" are everywhere on the certified side! But yet OM aircraft are not allowed to mingle south of the 49th because they will fall out of the sky! OM aircraft are not allowed for other reasons. Keep digging, eh! :)
 
Dan Thomas said:
RTV has been known to break free and get into places it doesn't belong and cause engine failures. It has no business inside an engine. Nowhere in Continental's approved sealants list do we find any silicone. https://www.cocotier.org/engines/continental/Service Bulletins/SB_Continental/sil99-2.pdf
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I don't believe this. Are you aware that RTV silicon sealant is the standard way of sealing in automotive automotive engines often in place of any gasket. Auto technology is years ahead of primitive aero engine technology. Why is it still being used in auto engines if it causes problems? I have never found a trace of RTV in my oil screen. You can live in the technical dark ages if you wish I go for progress.
 
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I’ve found tiny and larger bits of RTV in the oil pickup screen of a few car engines I’ve dismantled. I like to reduce risk and opportunities for failure. I’ll take a leaky oily engine, as long as it’s not a major leak. I wish it wouldn’t be messy, but it’s a machine and not a museum display. My worthless opinion...
 
Don't discount the possibility of a small hairline case crack when your doing your investigating.
 
BTW if TCM were so smart they would not have ADs. On a new Cessna 320 at 65 hours Total Time TSIO-470 I had an engine failure. I prefer thinking for myself. In fact as an aero engineer it's what's I am paid to do.
 
Silvaire said:
If you really want to find the source the best method is florescent dye, shows up under UV flashlight. You don't even need to clean it up beforehand. No guessing, it will be obvious.
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Unless you use Aeroshell. That glows under black light all by itself.
 
Tiny update:

Will be looking tomorrow (Saturday) as its my first time out there since I noticed it.

Someone mentioned case crack...you can bet that's been in my mind since I noticed all the oil. Hopefully not the case...lame but rather practical pun.

Interesting about the oil mess tending to migrate forward. The firewall was a mess.

I have no intents to apply RTV anywhere LOL!

Just trying to narrow down where its from. We don't have a mechanic on field so trying to first determine if we can safely fly it 15min to the shop or not.

Lots of great cleaning and inspecting suggestions!

Fingers crossed its something simple.
 
Snowmass said:
I don't believe this. Are you aware that RTV silicon sealant is the standard way of sealing in automotive automotive engines often in place of any gasket. Auto technology is years ahead of primitive aero engine technology. Why is it still being used in auto engines if it causes problems? I have never found a trace of RTV in my oil screen. You can live in the technical dark ages if you wish I go for progress.
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You can believe it or not. Makes no difference as far as reality is concerned. Strips of loose RTV can slither through the oil pickup screen and go into the pump and between those closely-fitting gear teeth and maybe crack them. RTV is tough stuff and can do that.

What the automotive manufacturers do has NO bearing on aviation practices. They do use RTV and they have procedures for doing so. If an engine fails due to RTV contamination, it doesn't cause a crash.

Lycoming and Continental have both learned a lot of stuff the hard way, and they've also seen a lot of owners learn a bunch more the hard way, which is why they publish documents outlining the acceptable stuff to use in various places. Those documents are FAA-approved. Anything outside those directions is seen by the feds as "unapproved" or "unacceptable" repairs, and if the NTSB finds stuff like that they can take it to court. You might be an "aero engineer" of some obscure sort but not an A&P. You're advising other owners to do unapproved stuff to their airplanes, which could be seen as a contributing cause to some accident. Legal exposure?

upload_2021-6-18_19-5-22.png
 
Snowmass said:
BTW if TCM were so smart they would not have ADs. On a new Cessna 320 at 65 hours Total Time TSIO-470 I had an engine failure. I prefer thinking for myself. In fact as an aero engineer it's what's I am paid to do.
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Where can I get me one of those 2021 Cessna 320s?

Aero engineer or not, I hope the newbies here aren't taking your advice seriously. This isn't a personal attack. I just don't think your aircraft maintenance knowledge or capability is on par with your engineering knowledge. Though, I envy you for the latter.

However, I seriously doubt your cumulative experience as an engineer holds a match to the hundreds of years of cumulative experience among engine manufacturers, IAs, and the FAA.

If you haven't attended a FAAST IA seminar near you, I strongly recommend you do so every chance you get. It's a cheap education and you don't have to be an IA to attend.
 
Aero engineer here too....also A&P I/A. Unless the maintenance manual or ICA sez it....don't do it.

Please don't put RTV inside your engine. It can cause problems later. If you have to go all redneck & Jerry rigging stuff....go with ProSeal on the "outside" of the engine (and do a neat job by masking off the area you're sealing).
 
Not one of you finger waggers has answered why today's billions of automotive engines deliberately use RTV silicon for engine sealing. I am waiting.

Progress does not result from doing things the same old way and modern auto engines are light years ahead of our 1935 TCM technology. Maybe some of you are too old to accept modern technology. I remember a long time ago when the FAA mandated primitive casein wood glues on wooden airplanes many mechanics used modern Weldwood glue instead. Were mechanics smarter then?
 
Snowmass said:
Are you aware that RTV silicon sealant is the standard way of sealing in automotive automotive engines often in place of any gasket.
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Just to add, but it's not the standard way of sealing in aviation engines. Matter of fact in a number of aircraft maintenance procedures it's actually forbidden to use silicone sealants as some silicone products are highly corrosive to the metal alloys found in aircraft type gearboxes, etc. Where silicone is called out by the OEM aero engineers its usually a non-acidic type and requires a specific P/N that not available to your average auto mechanic.
Snowmass said:
I am waiting.
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Corrosion and sealant migration are not issues in the automotive industry. But they are in the aviation industry. There's a number of references on these topics that you should have access to being an aero engineer.;)
 
Modern auto engines use lots of aluminum just like aero engines and use identical lubrication systems. Of course it's not the standard way of sealing in aircraft engines because aircraft engines use backward technology. That's why pushrod tubes often leak. I will bet anyone $1000 or $10,000 or more if they can show any damage to my IO-520 due to sealing the pushrod tubes with RTV. Open up your ossified minds.
 
Silvaire said:
If you really want to find the source the best method is florescent dye, shows up under UV flashlight. You don't even need to clean it up beforehand. No guessing, it will be obvious.
Click to expand...
I have used florescent dye for finding leaks in air conditioning, engine and hydraulic systems. Works well most of the time.
 
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