Treat oil leaks seriously

[MMM]

A story of complacency. Quite a few years ago we had a twin that was flying on a weekend at a very busy flight school/flying club. I was the mechanic and was working part-time so wasn't fully in the loop on everything. Pilots wanted me to check out one of the engines for having some oil on the cowling. All engines leak, but these Rotax 912 engines in particular were just always leaking a lot. Pretty low time engines that looked brand new, just leaked constantly.

Oil looked like as much as normal, told them to check oil level and if that was good it was okay, just a leaky engine. Unbeknownst to me that had just had some work done on it and a part was not clamped properly back on. Ended up getting a low oil pressure warning and they shut it down + declared emergency. Luckily it was a twin.

Ever since that day I make sure if any pilot says it's got too much oil, I pull the cowls off, check for leaks, and wash the aircraft. And if you are wondering, I was honest with that fact and they considered the problem with the improper maintenance done, but it definitely is something that fell on me at the end of the day.

 

[kmacht]

Engines aren’t designed to leak. If they do then something is wrong. If a mechanic tells me it’s just a leaky engine, can’t tell me where the leak is coming from and does nothing more than check the oil level I think I would be finding another mechanic. You are lucky you didn’t kill someone with your complacency.

 

[TCABM]

Engines aren’t designed to leak. If they do then something is wrong. If a mechanic tells me it’s just a leaky engine, can’t tell me where the leak is coming from and does nothing more than check the oil level I think I would be finding another mechanic. You are lucky you didn’t kill someone with your complacency.

We dealt with this past year in a O-320 that flies about 300hrs/yr. Small amount of oil on the cowling. Searched for that leak for 8+ months. Used dye in the oil, baby powder, you name it followed by 30+ min in the pattern.

Couldn’t find it, despite replacing all the oil return lines and oil cooler lines. Multiple very experienced A&Ps with engine overhaul experience tried every trick in the book.

Turns out the crack in the case was developing and as the case heated up on a cross country, there was enough expansion for a small amount (less than an ounce) to mist out, get caught in the airflow around the engine and make it’s way out of cowling.

Then, after a couple of back-to-back 3hr trips, I went out to pre-flight and the crack finally made it’s way to fully developed. About 3oz oil had seeped out, but it looked like a murder scene. Cleaned the engine and did the dye in the oil and the crack finally showed up.

In hindisght, the only thing we’d do different is order the exchange engine earlier, but there was no real smoking gun indicating the leak was getting worse, just a small streak on the cowling.

 

[Salty]

Now that I own a radial, this thread is kinda funny to me though it is really serious in context. My radial has an additional 4.5 gallons (yes gallons) of oil plus whatever is in the engine. Probably another gallon on the bottom of the plane. lol

 

[Capt. Geoffrey Thorpe]

If a 912 is leaking anything, something is wrong.

 

[Pinecone]

And if a radial is NOT leaking something, something is wrong.

 

[RyanShort1]

If a 912 is leaking anything, something is wrong.

Yes. 912s are a different animal.

 

[Lndwarrior]

My old lycoming O-235 "seeps" oil. I spent a very long time checking and replacing stuff to eliminate possible sources. It's been like this since I installed the engine 6 years and 600 hours ago. I think a small amount is from the sump gasket but at this time itn's not worth the time or effort to replace it. Also, it's not likely to complete eliminate every tiny drop of seepage.

At this point I know what is "normal" and what is not. I pull my cowl about every 10 hours or so to inspect the engine and oil seepage is part of that inspection. I do a thorough wipe down of any oil residue so I can keep track of the seepage. I use the term seepage because there are no "drops" of oil just a thin coating in certain specific areas.

I've heard mechanics say that any lycoming that has had the case apart will always leak some oil. There seems to be some truth in that.

If I had a rotax I would be more concerned. A fellow builder finished his RV about the same time as mine. You can still eat off his engine. I'd have to be really hungry to eat off of mine...

 

[Stewartb]

Pressure cowls make locating small oil leaks very difficult. Every situation is different. Use your judgement, and apparently be prepared to be judged.

 

[Daleandee]

Years ago after some maintenance on my Corvair conversion I found traces of oil on the belly after a short test flight. Thought it was a valve cover gasket or a pushrod o-ring, etc.

A fellow pilot suggested that since it was minimal that I should just fly it and keep an eye on it. I told him that if I knew where the leak was that might be a consideration but since I didn't know I had to find out.

At the end of the day it was a small leak coming from the oil cooler that I obvioulsy damaged during the work I was doing. I was relieved that I had found it and wondered what may have been the outcome if that small crack would have opened up in flight.

So the lesson is a good one. Engines should not leak ... although some do seep quite a bit!

 

[MauleSkinner]

And if a radial is NOT leaking something, something is wrong.

But if it’s leaking much, something is wrong as well.

Unfortunately, as the OP noted, complacency sets in. Often because of trite comments that people take out of context as undeniable truth.

 

[kaiser]

Not as bad as radials, but having a bunch of hours now behind the ole Conti O-300... if there's no oil under it, there's no oil in it...

 

[Dan Thomas]

Engines aren’t designed to leak. If they do then something is wrong. If a mechanic tells me it’s just a leaky engine, can’t tell me where the leak is coming from and does nothing more than check the oil level I think I would be finding another mechanic. You are lucky you didn’t kill someone with your complacency.

If they are recently overhauled, and properly maintained, they won't leak. But engines get old, their gaskets shrink and crack, the sealant on the case mating flanges ages and cracks, nitrile oil seals on the crank nose and vacuum pump drives (and alternator drives on the smaller Continentals) and tach drive all get old and lose their grip on the shafts and start leaking. Magneto gaskets get torn when mechanics reset the timing; one needs to take that mag off and replace the gasket to begin with. Otherwise the airplane will be back for that fix. On the Lycomings, the rocker box oil drain tubes are connected to nipples on the case by short sections of rubber hose that start leaking. They get very hot and are attacked by oil much hotter than what the oil temp gauges shows; that oil is coming from the head, after all. The Lycoming filler/dipstick tube comes loose when pilots overtighten that oil dipstick cap and the next guy has to use pliers or something to get it loose, torquing the whole tube and popping it loose at the bottom, against its lockwire. I used to take those out, install a new gasket with some Hi-Tack sealant and install them. That sealant would lock them in pretty good. And I showed the students and instructors that they didn't need to tighten that cap so much. Sometimes the crankcase breather tube cokes up with sludge formed from oil and water, and crankcase gases can't get out easily, pressurizing the case and forcing oil out of marginal areas. Checking that tube for free breathing is a Cessna inspection checklist item.

The flight school engines rarely went past three years, so leaks were seldom a problem. Most common were those oil drain tube hoses, easily replaced if you know how and have the right tool. Checking the torques on crankcase sump hardware will sometimes find them coming loose due to gasket shrinkage.

 

[kmacht]

If they are recently overhauled, and properly maintained, they won't leak. But engines get old, their gaskets shrink and crack, the sealant on the case mating flanges ages and cracks, nitrile oil seals on the crank nose and vacuum pump drives (and alternator drives on the smaller Continentals) and tach drive all get old and lose their grip on the shafts and start leaking. Magneto gaskets get torn when mechanics reset the timing; one needs to take that mag off and replace the gasket to begin with. Otherwise the airplane will be back for that fix. On the Lycomings, the rocker box oil drain tubes are connected to nipples on the case by short sections of rubber hose that start leaking. They get very hot and are attacked by oil much hotter than what the oil temp gauges shows; that oil is coming from the head, after all. The Lycoming filler/dipstick tube comes loose when pilots overtighten that oil dipstick cap and the next guy has to use pliers or something to get it loose, torquing the whole tube and popping it loose at the bottom, against its lockwire. I used to take those out, install a new gasket with some Hi-Tack sealant and install them. That sealant would lock them in pretty good. And I showed the students and instructors that they didn't need to tighten that cap so much. Sometimes the crankcase breather tube cokes up with sludge formed from oil and water, and crankcase gases can't get out easily, pressurizing the case and forcing oil out of marginal areas. Checking that tube for free breathing is a Cessna inspection checklist item.

View attachment 124243

The flight school engines rarely went past three years, so leaks were seldom a problem. Most common were those oil drain tube hoses, easily replaced if you know how and have the right tool. Checking the torques on crankcase sump hardware will sometimes find them coming loose due to gasket shrinkage.

You made my point. If the engine is leaking then something is wrong. It doesn't mean that the airplane needs to be immediately grounded but the mechanic needs to at least inspect the engine and figure out what is leaking and why. From there they can figure out how important it is to fix the leak and how quickly it needs to be done.

 

[Hengelo]

Found oil (constant speed prop) slung onto the prop, cowling and windshield today - so I scrubbed the flight, called the club. Scary.

 

[Kesk]

Found oil (constant speed prop) slung onto the prop, cowling and windshield today - so I scrubbed the flight, called the club. Scary.

Any oil on the prop and it needs an overhaul, even a tiny bit. Least that's what I've always seen.

 

[Tools]

So there I was…

Ferrying a Pietenpol (a-65 engine) from Helena to Chicago. FIRST STOP oil leaking everywhere. Seller was a a&p IA who built the thing didn’t say anything about it. Called him, we agreed prolly just pushrod tubes. Lots of fuel stops, just keep it topped off…

Made the three day trip just fine, BUT…. Was a three inch crack in the engine case. An ounce more of cynicism woulda found it rather than biasing towards what I WANTED it to be.

Lesson learned.

 

[Zeldman]

A long, long tome ago I was flying cancelled checks in a 210 out of Bessemer, Al. Checks.?? what are those.?? Told ya it was a long time ago...

At the first stop I found oil down the right side of the plane. I wiped it off and looked for an oil leak. None found. I checked the oil level, same as before takeoff.

Next stop, same thing. No change in oil level. I wiped it off and continued.

Third stop, same thing.Again, no change in oil level. Wiped it clean and continued.

Got back to base about 6am, same thing, oil down the right side. Checked oil, no change in level. So I wrote it up in the plane log and showed it to the early mechanic.

The next day I talked to the mechanic that worked on it. There was a tiny crack in the oil cooler that let oil out the right side of the plane making a big mess. I mean every time I saw the oil down the side of the plane I expected the engine to be bone dry. It doesn't take much oil in the air stream to make a big, big mess.

My bag of luck emptied a little that night. That little crack could have turned into a very big crack and then the fun would have started...

 

[Dave Arata]

Not as bad as radials, but having a bunch of hours now behind the ole Conti O-300... if there's no oil under it, there's no oil in it...

The ol Harley adage.

 

[DavidWhite]

This was an IO520F, being flown primarily over very cold water or mountains. I generally didn’t fly this airplane, but the pilot who usually did was sick and I ended up assigned to the aircraft. When I walked up to it I noticed some oil on the ground and leaking down the nosegear, I called the guy who usually flew it, asked if this was “normal” and he said yes it had been leaking for the last week or so he’d been flying it. I said well there’s nothing normal about a new oil leak, so we pulled the cowl and found this. The crack actually went all the way to the spine of the engine underneath the magnetos.

Nothing “normal” about an oil leak.

 

[Zeldman]

This was an IO520F, being flown primarily over very cold water or mountains. I generally didn’t fly this airplane, but the pilot who usually did was sick and I ended up assigned to the aircraft. When I walked up to it I noticed some oil on the ground and leaking down the nosegear, I called the guy who usually flew it, asked if this was “normal” and he said yes it had been leaking for the last week or so he’d been flying it. I said well there’s nothing normal about a new oil leak, so we pulled the cowl and found this. The crack actually went all the way to the spine of the engine underneath the magnetos.

Nothing “normal” about an oil leak.


View attachment 124648

YIKES.!!

 

[flyingpreacher]

We dealt with this past year in a O-320 that flies about 300hrs/yr. Small amount of oil on the cowling. Searched for that leak for 8+ months. Used dye in the oil, baby powder, you name it followed by 30+ min in the pattern.

Couldn’t find it, despite replacing all the oil return lines and oil cooler lines. Multiple very experienced A&Ps with engine overhaul experience tried every trick in the book.

Turns out the crack in the case was developing and as the case heated up on a cross country, there was enough expansion for a small amount (less than an ounce) to mist out, get caught in the airflow around the engine and make it’s way out of cowling.

Then, after a couple of back-to-back 3hr trips, I went out to pre-flight and the crack finally made it’s way to fully developed. About 3oz oil had seeped out, but it looked like a murder scene. Cleaned the engine and did the dye in the oil and the crack finally showed up.

In hindisght, the only thing we’d do different is order the exchange engine earlier, but there was no real smoking gun indicating the leak was getting worse, just a small streak on the cowling.

I'm currently stranded at KBQK due to a VERY similar sounding issue. Very little bit of oil streaking back along the cowling for the last year+ and the three A&Ps who have looked at it suggest a leaking crankshaft seal. They've told us it isn't a big deal, so we planned to have it replaced at annual later this month. After back to back 3 hour legs, I had oil all down the side of the fuselage. Sent our IA the picture and he said he no longer thinks it's a crankshaft seal, but probably something on the left side of the engine. It's not going anywhere until an A&P looks at it here, but it sounds eerily similar to your story.

 

[Racerx]

Any oil on the prop and it needs an overhaul, even a tiny bit. Least that's what I've always seen.

No. It could be a stuck zerk.

 

[AV8R_87]

I'm currently stranded at KBQK due to a VERY similar sounding issue. Very little bit of oil streaking back along the cowling for the last year+ and the three A&Ps who have looked at it suggest a leaking crankshaft seal. They've told us it isn't a big deal, so we planned to have it replaced at annual later this month. After back to back 3 hour legs, I had oil all down the side of the fuselage. Sent our IA the picture and he said he no longer thinks it's a crankshaft seal, but probably something on the left side of the engine. It's not going anywhere until an A&P looks at it here, but it sounds eerily similar to your story.

Had a similar issue. In my case it was a leaking pushrod tube seal (crankcase-side). Monitored and deferred it until the prop had to come off for a hollow crankshaft inspection AD, since the nose bowl had to come off to pull that rocker cover.

 

[flyingpreacher]

Had a similar issue. In my case it was a leaking pushrod tube seal (crankcase-side). Monitored and deferred it until the prop had to come off for a hollow crankshaft inspection AD, since the nose bowl had to come off to pull that rocker cover.

That's what we were doing - deferring until annual when we were going to take care of it. Not sure what we'll do now. I reckon we'll find out more tomorrow when the local A&P can look at it.

 

[TCABM]

I'm currently stranded at KBQK due to a VERY similar sounding issue…

There’s only a handful of places a leak can develop. What we hypothesize is that the longer cross countries were allowing the case and the oil to heat up enough to seep through and then get caught in the air flow around the engine before being expelled. These longer durations at higher temps and power were allowing the crack to slowly expand before it became detectable when cold/troubleshooting.

As I mentioned, we troubleshot ours for close to a year before we found the smoking gun, but it was a lucky and catastrophic find. We had planned to order a new engine anyways, but kind of got lulled into let’s trace the leak.

Given lead times, if you’re planning on an exchange, I’d pull the trigger now.

 

[flyingpreacher]

There’s only a handful of places a leak can develop. What we hypothesize is that the longer cross countries were allowing the case and the oil to heat up enough to seep through and then get caught in the air flow around the engine before being expelled. These longer durations at higher temps and power were allowing the crack to slowly expand before it became detectable when cold/troubleshooting.

As I mentioned, we troubleshot ours for close to a year before we found the smoking gun, but it was a lucky and catastrophic find. We had planned to order a new engine anyways, but kind of got lulled into let’s trace the leak.

Given lead times, if you’re planning on an exchange, I’d pull the trigger now.

So it turned out that the crankshaft seal was so loose it could be wiggled with a finger. There was NO sealant around the seal. It has been replaced and sealed and we are on our way again tomorrow!

 

[AV8R_87]

Awesome news! Safe travels!

 

[traumamed]

This thread started with an A&P fessing up to an instance of complacency, but there is an important second side to this story that hasn't been directly discussed - the pilots. They elected to take a plane up even after having suspicion of an issue. They did so because they thought, "ok, an A&P checked it out, it must be fine." Is that not also a bit of complacency on the part of the PIC? And so begins my own guilty anecdote of how I learned, luckily not the hard way, to trust but verify. Long story follows.

I was on a long XC from FL to SD in my old Arrow, with an A&P as my passenger tagging along to get a ride to his summer house. At the second-to-last stop for my pax, I topped up the oil. He asked what I was bringing it up to, and I said "8 qts." He shook his head and said I'd have a quart out the breather and on my belly by the time I dropped him off at the next stop. Sure enough, I land at his home airport and there was oil all over the bottom cowl and bottom of the fuselage. He chuckles and tells me, "Told ya so. Recheck your oil and you'll have exactly 7 qts." He was spot on, again. So, confirmation bias in full effect, I bid him farewell and continued on my final short hop of ~80 miles to my final destination.

After an uneventful 40ish minute flight, I hop out on the ramp to be greeted by this:

I recheck the oil and I'm down to 5.5 qts, so lost 1.5 qts in 40 mins. This freaks me out, because now I'm forced to accept that I just flew a plane that was trying to tell me something was up, and I ignored it. My A&P-rated pax brushed it off, so I did too. Complacency.

But wait - it gets better! One of my pilot buddies at this particular airport gets his A&P on the fix. A couple days later, I get a call from that A&P telling me my oil dipstick tube was super loose and barely hanging on, so he got it tightened up, problem solved. Whew. No major $$$$ mechanical issue, and no harm done. Plane sits on the ramp another week before I fly out, and when I return, no oil under it - great sign. So I trust that A&P had fixed it, and I merrily set off on a XC from the middle of SD to Minneapolis. Imagine my horror when I land in Minneapolis a couple of hours later to see the oil-hemorrhage saga was not over. I had lost 4 qts in that flight. Another 30-60 mins and I may well have been facing a catastrophic engine failure.

Finally, I decide to take the cowl off myself and have a look. It took me all of two minutes to find the #3 cylinder oil return line had been rubbing on a nearby piece of sheet metal and nearly sawed itself in half. Two days to get the part and 30 minutes of work and the real reason for the leak was fixed.

I put my blind trust in not one, but two different A&Ps. I don't think either meant to miss the problem, but stuff happens. Remember, you're the PIC, and it's you and your loved ones up there, not the A&P. I have since become a much more involved owner.

 

[flyingpreacher]

This thread started with an A&P fessing up to an instance of complacency, but there is an important second side to this story that hasn't been directly discussed - the pilots. They elected to take a plane up even after having suspicion of an issue. They did so because they thought, "ok, an A&P checked it out, it must be fine." Is that not also a bit of complacency on the part of the PIC?

This is a fair point and one of which I (as the PIC mentioned above) am definitely guilty. But I would ask the other side of the same question. I noticed an issue, and since I am not an airplane mechanic, I took it to someone who was. He identified the issue but said it was not necessary to deal with until annual. The problem persisted, so I got a second (and in turn third) opinion. All said the same thing.

I honestly probably have less excuse than others as I am more mechanically inclined and could have looked into it myself further, but since the ultimate issue ended up being exactly what all three mechanics identified, I probably would have trusted their judgment anyway.

That being said, what would you advise for a pilot who is not mechanically inclined in the same circumstance? He noticed an issue (Good job in your PIC duties) and took it to a mechanic (Good decision) and when the problem persisted, he followed up by getting a second and third opinion (good decision). To that point, he has taken the steps that a non-mechanical pilot would naturally assume are adequate. (Again, I'm not justifying myself, as I could have been more proactive.) He hasn't been complacent in his PIC responsibilities, he has been active in addressing them, but without going to A&P school (which as a non-mechanical person would be extremely difficult!) what else would you suggest he do?

 

[SixPapaCharlie]

We dealt with this past year in a O-320 that flies about 300hrs/yr. Small amount of oil on the cowling. Searched for that leak for 8+ months. Used dye in the oil, baby powder, you name it followed by 30+ min in the pattern.

Couldn’t find it, despite replacing all the oil return lines and oil cooler lines. Multiple very experienced A&Ps with engine overhaul experience tried every trick in the book.

Turns out the crack in the case was developing and as the case heated up on a cross country, there was enough expansion for a small amount (less than an ounce) to mist out, get caught in the airflow around the engine and make it’s way out of cowling.

Then, after a couple of back-to-back 3hr trips, I went out to pre-flight and the crack finally made it’s way to fully developed. About 3oz oil had seeped out, but it looked like a murder scene. Cleaned the engine and did the dye in the oil and the crack finally showed up.

In hindisght, the only thing we’d do different is order the exchange engine earlier, but there was no real smoking gun indicating the leak was getting worse, just a small streak on the cowling.

can you elaborate on the baby power, and other tests or DM me. I have had a leak for 2 years. 3 people have looked and we cannot find the source.

 

[TCABM]

can you elaborate on the baby power, and other tests or DM me. I have had a leak for 2 years. 3 people have looked and we cannot find the source.

I’ll send you the info after I get in the office.

 

[traumamed]

...
That being said, what would you advise for a pilot who is not mechanically inclined in the same circumstance? He noticed an issue (Good job in your PIC duties) and took it to a mechanic (Good decision) and when the problem persisted, he followed up by getting a second and third opinion (good decision). To that point, he has taken the steps that a non-mechanical pilot would naturally assume are adequate. (Again, I'm not justifying myself, as I could have been more proactive.) He hasn't been complacent in his PIC responsibilities, he has been active in addressing them, but without going to A&P school (which as a non-mechanical person would be extremely difficult!) what else would you suggest he do?

Your point is well taken. This touches on the fiduciary duty, per se, of the skilled professional. One ultimately has to trust that the people hired to accomplish complex tasks know what they are doing. Still, blind faith in someone else's work is not a strategy.

We sump our fuel everytime a line guy fills our tanks, right? Shouldn't we also look to see the oil drain plug is secure and safetied after an oil change? Verify work where possible.

In my example, the danger of the leak leaving my sump dry could have been minimized if I would have flown a quick 10-15 mins near an airport and then landed to make sure there was no ongoing leak before setting off on XCs. Faith =/= trust.

 

[Baked Potato]

How about coolant?
The rotax LSA I fly often has no coolant in the reservoir during pre-flight, with no trace of it anywhere upon visible inspection. Meaning that it went somewhere during the last flight. Nobody else at the school seems too concerned - it's just filled up again and we're ready to go.

 

[TCABM]

[mention]SixPapaCharlie [/mention] the baby powder check is a poor man’s NDT. Clean the engine with mineral spirits the finely dust with baby powder in the suspect areas and do a test run or better, a lap in the pattern or two and then decowl and take a look.

For the flourescent dye, here’s a an overview from AOPA on the process.

Aircraft Maintenance: Black lights aren’t just for parties

A simple black light can be a useful tool when checking your aircraft's engine for leaks.

www.aopa.org

Essentially, a fluorescent dye is added to the oil, do a short test flight, decowl and turn on the black light to find the ‘hot’ spots.

Finding the suspect area and figuring out how long it takes for the oil to start leaking is the most frustrating part.

 

[mandm]

This is a fair point and one of which I (as the PIC mentioned above) am definitely guilty. But I would ask the other side of the same question. I noticed an issue, and since I am not an airplane mechanic, I took it to someone who was. He identified the issue but said it was not necessary to deal with until annual. The problem persisted, so I got a second (and in turn third) opinion. All said the same thing.

I honestly probably have less excuse than others as I am more mechanically inclined and could have looked into it myself further, but since the ultimate issue ended up being exactly what all three mechanics identified, I probably would have trusted their judgment anyway.

That being said, what would you advise for a pilot who is not mechanically inclined in the same circumstance? He noticed an issue (Good job in your PIC duties) and took it to a mechanic (Good decision) and when the problem persisted, he followed up by getting a second and third opinion (good decision). To that point, he has taken the steps that a non-mechanical pilot would naturally assume are adequate. (Again, I'm not justifying myself, as I could have been more proactive.) He hasn't been complacent in his PIC responsibilities, he has been active in addressing them, but without going to A&P school (which as a non-mechanical person would be extremely difficult!) what else would you suggest he do?

I’d start by learning how to take the cowling off, an oil change and safety wire. Have another experienced pilot or A&P supervise you. Then you can add some mx steps along the way as you feel more comfortable. Take it slow is key.

 

[fast99]

[mention]SixPapaCharlie [/mention] the baby powder check is a poor man’s NDT. Clean the engine with mineral spirits the finely dust with baby powder in the suspect areas and do a test run or better, a lap in the pattern or two and then decowl and take a look.

For the flourescent dye, here’s a an overview from AOPA on the process.

Aircraft Maintenance: Black lights aren’t just for parties

A simple black light can be a useful tool when checking your aircraft's engine for leaks.

www.aopa.org

Essentially, a fluorescent dye is added to the oil, do a short test flight, decowl and turn on the black light to find the ‘hot’ spots.

Finding the suspect area and figuring out how long it takes for the oil to start leaking is the most frustrating part.

I have used dye on oil leaks and AC leaks in automobiles. It will almost immediately show with a black light. Actually, biggest problem with dye is waiting too long to put a light on it. The dye gets everywhere, then becomes hard to locate the source.

 

[TCABM]

I have used dye on oil leaks and AC leaks in automobiles. It will almost immediately show with a black light….

Our leak did not, at least not until it was too late.

Prior to that, even with a start, taxi, and run up, dye was not showing, but our case crack was in unique place that required some time for the migration to occur. But yeah, there’s a fine line between Goldilocks and floodgates.

 

[BMan]

This thread started with an A&P fessing up to an instance of complacency, but there is an important second side to this story that hasn't been directly discussed - the pilots. They elected to take a plane up even after having suspicion of an issue. They did so because they thought, "ok, an A&P checked it out, it must be fine." Is that not also a bit of complacency on the part of the PIC? And so begins my own guilty anecdote of how I learned, luckily not the hard way, to trust but verify. Long story follows.

I was on a long XC from FL to SD in my old Arrow, with an A&P as my passenger tagging along to get a ride to his summer house. At the second-to-last stop for my pax, I topped up the oil. He asked what I was bringing it up to, and I said "8 qts." He shook his head and said I'd have a quart out the breather and on my belly by the time I dropped him off at the next stop. Sure enough, I land at his home airport and there was oil all over the bottom cowl and bottom of the fuselage. He chuckles and tells me, "Told ya so. Recheck your oil and you'll have exactly 7 qts." He was spot on, again. So, confirmation bias in full effect, I bid him farewell and continued on my final short hop of ~80 miles to my final destination.

After an uneventful 40ish minute flight, I hop out on the ramp to be greeted by this:

View attachment 129011
I recheck the oil and I'm down to 5.5 qts, so lost 1.5 qts in 40 mins. This freaks me out, because now I'm forced to accept that I just flew a plane that was trying to tell me something was up, and I ignored it. My A&P-rated pax brushed it off, so I did too. Complacency.

But wait - it gets better! One of my pilot buddies at this particular airport gets his A&P on the fix. A couple days later, I get a call from that A&P telling me my oil dipstick tube was super loose and barely hanging on, so he got it tightened up, problem solved. Whew. No major $$$$ mechanical issue, and no harm done. Plane sits on the ramp another week before I fly out, and when I return, no oil under it - great sign. So I trust that A&P had fixed it, and I merrily set off on a XC from the middle of SD to Minneapolis. Imagine my horror when I land in Minneapolis a couple of hours later to see the oil-hemorrhage saga was not over. I had lost 4 qts in that flight. Another 30-60 mins and I may well have been facing a catastrophic engine failure.

Finally, I decide to take the cowl off myself and have a look. It took me all of two minutes to find the #3 cylinder oil return line had been rubbing on a nearby piece of sheet metal and nearly sawed itself in half. Two days to get the part and 30 minutes of work and the real reason for the leak was fixed.

I put my blind trust in not one, but two different A&Ps. I don't think either meant to miss the problem, but stuff happens. Remember, you're the PIC, and it's you and your loved ones up there, not the A&P. I have since become a much more involved owner.

You are so very lucky indeed! At my first part 141 school I found quarts of oil all over the engine and ground on a 172S during my preflight. The oil cap threads were stripped and the integrated cap/level-indicator sat loosely on the filler tube where oil obviously spit out all over on previous flights then pooled on the ground overnight. The oil level was at the full mark which means someone kept filling it. So, I commence to squawk and ground the plane for safety. A CFI nearby (mine hadn't arrived yet) in the hangar laughed at me and told me they "just duct tape that one" like they'd been doing the past few weeks and it'll be fine. As a hobbyist automotive engine builder who several times saw race car oil leaks start fires, I wanted to slug them. An engine out I'm prepared to handle but a fire wipes out options in a hurry. If I've learned one thing during training, being PIC means safety is ultimately ALL on the PIC no matter what an A&P or anyone else says.

 

[flyingpreacher]

I’d start by learning how to take the cowling off, an oil change and safety wire. Have another experienced pilot or A&P supervise you. Then you can add some mx steps along the way as you feel more comfortable. Take it slow is key.

This is good advice, and as someone who has always done my own (car) oil changes until my wife's newest car, I think that is among the easiest tasks to undertake, but people usually pay for the convenience. My question was more to the point of: if you aren't mechanically inclined and you encounter this problem, so you take it to a "professional" and he (or in this case all three) tells you that it isn't a big deal and just take care of it at annual, what additional steps could or should he take?

I totally agree with the sentiments expressed, so this is not for argument's sake, just for those who may visit this thread later, or for those of us in discussion to better arm ourselves for the future. He didn't blindly trust the first A&P he sought out a second and third opinion. What additional steps do you feel like he could take to better safeguard himself and his passengers?

As a note, I'm very thankful that my lack of proactivity didn't have more serious consequences. My wife and (at the time unborn) son were onboard with me. I am now much more aware of problems that arise and I want to be more proactive in the future, which is why I'm trying to further the discussion!