Oil leak or blowout?

[jmarine225]

In my never ending quest to figure this out, I have a 1969 Cherokee which was using a lot of oil. Long story short, had a crack in cylinder number 3 and it was replaced. I’ve been putting hours on it and the oil consumption during breakin has Improved so far to 4-5 hours per quart, after 5 hours. Now looking at the photos, where could that oil on the wheel pant be coming from? Is it blowoff as it was filled up to 7 during the last flight? There are no obvious leaks inside the engine compartment. Clean and dry. Also, the engine has chrome cylinders.

 

[Timbeck2]

Which side is your breather tube on? By just looking at oil on your wheel pant, it makes it very difficult to determine where the oil is coming from. Your best bet is to clean the engine thoroughly and then fly it and then come back to see where the oil is coming from. On that side, be sure to check the dipstick gasket at the bottom, make sure it isn't a residual spill when the oil was added, and finally check the oil return lines where it goes from the hard line to rubber at the sump. Those rubber hoses usually don't last too long before they start leaking. I don't fill mine over 6 quarts because it will just blow it out the breather tube.

 

[Unit74]

If the belly is clean, it's not blowing out. Those are clearly drips. Locate the breather tube and see if it's wet and could drip there. My plane always drip out of the breather after shutdown. If not, the Easter egg hunt begins. KLast resort, dye the oil and use a black light to find the source.

 

[jmarine225]

If the belly is clean, it's not blowing out. Those are clearly drips. Locate the breather tube and see if it's wet and could drip there. My plane always drip out of the breather after shutdown. If not, the Easter egg hunt begins. KLast resort, dye the oil and use a black light to find the source.

Ironically mine appears to be the same. When I shut it down there’s nothing there I come back the next day and there’s a drip coming from the engine compartment in

 

[3393RP]

Ironically mine appears to be the same. When I shut it down there’s nothing there I come back the next day and there’s a drip coming from the engine compartment in

Your post reminded me of a truly evil gag I pulled on a co-worker. It being the late 90s, when everyone had to own a Harley, Randy had just purchased a new Bourget Python chopper for $47,000. He was keeping the bike in my shop until he moved from an apartment to a house.

One Sunday afternoon I was at work, and while checking the back door to make sure it was locked, the chopper caught my eye. Hmmm....

I opened a quart of ATF, and poured a good sized puddle right underneath the transmission. I used ATF because its bright red color would add some urgency to the discovery of the "oil leak."



I came in early Monday, because I wanted to hear the shriek of horror when Randy saw his expensive bike emulating the Exxon Valdez. It wasn't long in coming, and the cry of anguish had a pitch and volume that far exceeded expectations.

Needless to say it took a while to calm Randy. Of course when he found out he had been punked, he was mad as hell. But the gag made everyone else howl in laughter.

His bike was similar to this:

I'm laughing right now, just thinking of that screech Randy let go when he saw the puddle of ATF under his pride and joy.

 

[Hang 4]

That looks like oil that got into the cowling and pooled up during an oil change. Likely from the filter change. I'd pull the lower cowling and give it a thorough cleaning and see if it goes away.

 

[Dan Thomas]

In my never ending quest to figure this out, I have a 1969 Cherokee which was using a lot of oil. Long story short, had a crack in cylinder number 3 and it was replaced. I’ve been putting hours on it and the oil consumption during breakin has Improved so far to 4-5 hours per quart, after 5 hours. Now looking at the photos, where could that oil on the wheel pant be coming from? Is it blowoff as it was filled up to 7 during the last flight? There are no obvious leaks inside the engine compartment. Clean and dry. Also, the engine has chrome cylinders.

4 to 5 hours per quart is bad. Sounds like the rings are all shot and the blowby is carrying oil mist out of the breather and making that mess.

The O-320s don't like to be filled. They will blow out oil if they're topped right up. In the 172s we ran the oil between 6 and 7.

If that oil leak wasn't there before the cylinder repair, it's very possible that the reinstallation was messed up somehow. You'd need to clean that engine off like Timbeck2 says, and fly it briefly and then look it over real well. There are numerous places oil could be coming out: where the cylinder base meets the crankcase (bad or pinched base o-ring seal), at either end of either of the valve pushrod tubes, between the case and the cylinder head, or, like Tim, said, at the oil return line, either at the rubber hose or at the nut on the fitting at the head. The hose clamp and/or nut might never have been properly tightened. Might even be a leaking rocker cover gasket. I hope the mechanic didn't reuse any of those seals.

 

[RyanB]

4 to 5 hours per quart is bad. Sounds like the rings are all shot and the blowby is carrying oil mist out of the breather and making that mess.

Agree. I’d be pretty heebed if I put a new cyl on and was still getting such poor oil consumption. In fact, I’d be far more concerned with the oil consumption than I would be with a little breather drool, which in most cases is perfectly normal. Solve the real problem first, before worrying about trivial matters such as this.

 

[jmarine225]

Agree. I’d be pretty heebed if I put a new cyl on and was still getting such poor oil consumption. In fact, I’d be far more concerned with the oil consumption than I would be with a little breather drool, which in most cases is perfectly normal. Solve the real problem first, before worrying about trivial matters such as this.

As far as the oil consumption, I was told by the mechanic and in the Lycoming paperwork, high oil consumption is to be expected during the break in period, which is up to 20 hours or whenever the consumption stabilizes. Since the cylinder replacement I’ve only put approximately 5 hours on the engine. Besides this, I have chrome cylinders. I was told with the chrome cylinders my engine oil consumption would be higher than normal, with 5 hours per quart being around the normal range.

 

[jmarine225]

4 to 5 hours per quart is bad. Sounds like the rings are all shot and the blowby is carrying oil mist out of the breather and making that mess.

The O-320s don't like to be filled. They will blow out oil if they're topped right up. In the 172s we ran the oil between 6 and 7.

If that oil leak wasn't there before the cylinder repair, it's very possible that the reinstallation was messed up somehow. You'd need to clean that engine off like Timbeck2 says, and fly it briefly and then look it over real well. There are numerous places oil could be coming out: where the cylinder base meets the crankcase (bad or pinched base o-ring seal), at either end of either of the valve pushrod tubes, between the case and the cylinder head, or, like Tim, said, at the oil return line, either at the rubber hose or at the nut on the fitting at the head. The hose clamp and/or nut might never have been properly tightened. Might even be a leaking rocker cover gasket. I hope the mechanic didn't reuse any of those seals.

The engine was cleaned and ran with no leaks being found. Since the cylinder replacement, no Oil is observed inside the cowling at all, where a leak would be suspected. Just a drop or so streaking down the wheel pant under the breather tube. Curious why that would happen after shutdown? Also, two separate mechanics looked at it and both came up with the one bad cylinder which needed replacement. All cylinders have compressions in the 70’s with no obvious leaks. The day of this pic we had it filled to almost 7 quarts on the O-320

 

[brcase]

Try running between 5.5 and 6 qts for a bit, if it stops dripping and using oil it is blow off. Then you can try between 6 and 6.5 qt (more typical) if you like.

Brian

 

[Domenick]

Check the crank nose seal.

How have you been breaking-in? 75+% power, no pattern work, no long idles or taxis?

I've never had chrome cylinders.
Anyone else can to comment on chrome cylinders, piston rings, and/or oil consumption?

 

[jmarine225]

Check the crank nose seal.

How have you been breaking-in? 75+% power, no pattern work, no long idles or taxis?

I've never had chrome cylinders.
Anyone else can to comment on chrome cylinders, piston rings, and/or oil consumption?

Been doing the break in as per lycoming recommnedations. 75% power, doing shorter cross countries. Nose seal was checked after power washing the engine. No leaks.

 

[kyleb]

My RV-6’s O-320 started spitting a little oil out of the breather days after flying. Park the airplane in the hangar after flying, a day later - no oil under the airplane. Three days later, a spot of oil the size of a computer mouse (odd analogy, I know) is under there, seemingly from the breather.

 

[bkspero]

...Since the cylinder replacement, no Oil is observed inside the cowling at all, where a leak would be suspected. Just a drop or so streaking down the wheel pant under the breather tube. Curious why that would happen after shutdown?...

There is a mist of oil drops in the crank case and leaving through the breather (pushed out the breather by blow-bay gases). It seems reasonable to me that a portion of those drops impact the walls of the breather tube and coat it with oil. That oil coating drains down and out the end of the breather tube as larger drops. In flight those larger oil drops, along with some of the oil mist, are blown along the underside of the fuselage by relative wind where the oil creates oil streaks. After shutdown, the oil coating on the breather continues to drain and drips from the end of the breather tube onto the front gear wheel pant of your airplane.

 

[jmarine225]

There is a mist of oil drops in the crank case and leaving through the breather (pushed out the breather by blow-bay gases). It seems reasonable to me that a portion of those drops impact the walls of the breather tube and coat it with oil. That oil coating drains down and out the end of the breather tube as larger drops. In flight those larger oil drops, along with some of the oil mist, are blown along the underside of the fuselage by relative wind where the oil creates oil streaks. After shutdown, the oil coating on the breather continues to drain and drips from the end of the breather tube onto the front gear wheel pant of your airplane.

Thanks for this explanation which makes the most sense to me as oil is not there During shutdown but a streak of oil appears a day or so later. Given this explanation, I can only assume, and hope, this is all normal? The mechanics aren’t concerned at all.

 

[Gary Ward]

In my never ending quest to figure this out, I have a 1969 Cherokee which was using a lot of oil. Long story short, had a crack in cylinder number 3 and it was replaced. I’ve been putting hours on it and the oil consumption during breakin has Improved so far to 4-5 hours per quart, after 5 hours. Now looking at the photos, where could that oil on the wheel pant be coming from? Is it blowoff as it was filled up to 7 during the last flight? There are no obvious leaks inside the engine compartment. Clean and dry. Also, the engine has chrome cylinders.

IMO 5 hours is not enough to seal rings to chrome cyls. IMO 75% power is not enough, I would have run it wide open throttle for at least an 1/2 hour after the first 2 hrs. I would run it more at WOT now at low altitudes.

When doing oil changes on my 320 it get's 7 qts added and shows 6 qts on the dip stick because the filter and cooler holds close to a qt. When it get's down to 5 on the stick I add another qt. I have never seen it read 7 on the dip stick and I would expect it to blow out if I had filled to 7 on the dip stick.

My buddy has a cheerokee with a 320 that has about 1100 hrs on it. Two years ago it did get one clys replaced because they found a crack. He is obsessed with tracking his oil usage, obsessed. He checks it non stop before and after flying, always concerned with his oil usage. He comes back to the hangar to check the oil after flying so the oil has time to drain back into the sump. He is burning 1 qt every 4-5 hrs. He wants to replace more cyls to improve his oil usage. His mechanic is his best friend and is fine with his oil consumption does not want to replace more clys. I helped do the leakdown last summer during his annual. They all leak 75 or better. His mechanic maintains a fleet of cheiftains and replaces lots of clys for 35 years now, much experience.

I kidd my buddy that his oil usage is increased because he is always checking his oil. Every time he checks it, a little get's wiped off the dip stick onto a paper towel and not being burn or sprayed out the vent tube. Also he has at least one leak out of the accessory case that his mechanic does not seemed worried about. That adds to his oil consumption. Has a drip tray under his nose strut in his hangar.

 

[pburger]

"4-5 hours per quart, after 5 hours"

Umm... two things
1) you say the oil consumption has improved, but you've only run 5 hours? This doesn't make sense. Improved from what? I think there is a typo somewhere. Was that supposed to be "4-5 hours per quart after 50 hours"?
2) 1 quart in 4-5 hours is not terrible. If you had 4 new cylinders, then it should be better than this (after break-in). You've got 1 new cylinder -- how old are the others?

 

[Domenick]

...My buddy has a cheerokee with a 320 that has about 1100 hrs on it. Two years ago it did get one clys replaced because they found a crack. He is obsessed with tracking his oil usage, obsessed. He checks it non stop before and after flying, always concerned with his oil usage. He comes back to the hangar to check the oil after flying so the oil has time to drain back into the sump. ...

I also religiously track my oil usage but only before each flight during preflight. That's when it matters and when you would add oil. This tracking helped me decide to retire my old O-320. Developed a spreadsheet to track oil consumption and oil changes.

 

[jmarine225]

"4-5 hours per quart, after 5 hours"

Umm... two things
1) you say the oil consumption has improved, but you've only run 5 hours? This doesn't make sense. Improved from what? I think there is a typo somewhere. Was that supposed to be "4-5 hours per quart after 50 hours"?
2) 1 quart in 4-5 hours is not terrible. If you had 4 new cylinders, then it should be better than this (after break-in). You've got 1 new cylinder -- how old are the others?

Sorry. Didn’t seem that confusing to me and/or the others posters on here. Oil consumption improved after replacing the cracked cylinder.

 

[Dan Thomas]

Sorry. Didn’t seem that confusing to me and/or the others posters on here. Oil consumption improved after replacing the cracked cylinder.

Oh, boy. How bad was it before the cylinder was replaced?

I once towed gliders with an old Auster AOP6. deHavilland Gipsy Major 7 145-hp inverted inline aircooled engine. It burned a quart per hour of Aeroshell 100. We switch to Texaco aviation oil and the consumption went to 1/2 quart per our. Huge improvement, but still really bad. I later bought the airplane after it got damaged (by another pilot, who suffered a fuel-related engine failure) and after opening up the engine I found that the pistons and cylinders were badly worn. Clearances big enough to drive a truck through. Good thing it had a 12-quart oil tank.

 

[Checkout_my_Six]

Is the belly oily?

 

[jmarine225]

I believe I have the oil thing figured out now. Besides that I was following the lycoming protocols for a new cylinder break in. It says to open the throttle up to full for approximately 30 minutes while in cruise. I’m guessing my tach must be off, but in a flight today when I did it, the tach was at 3000 rpm.

 

[Gary Ward]

I believe I have the oil thing figured out now. Besides that I was following the lycoming protocols for a new cylinder break in. It says to open the throttle up to full for approximately 30 minutes while in cruise. I’m guessing my tach must be off, but in a flight today when I did it, the tach was at 3000 rpm.

Like I said above, WOT...WFO! lol

 

[Jeff767]

I believe I have the oil thing figured out now. Besides that I was following the lycoming protocols for a new cylinder break in. It says to open the throttle up to full for approximately 30 minutes while in cruise. I’m guessing my tach must be off, but in a flight today when I did it, the tach was at 3000 rpm.

I would get your tach checked. You can probably borrow a handheld tach. 3000 RPM is high. Either the tach is off or the aircraft is poorly propped. Regardless I would not exceed 2700 even during break in.

 

[Chip Sylverne]

Rig up a rubber cork with a plastic tube in it that will run back to the cockpit. Safety wire the cork into the oil fill hole and put a digital digital manometer on the cockpit end of the tube. Fly around the pattern. Lycoming has a spec for internal crankcase pressure, I believe it's 1.5" we, but don't quote me on that. You can use an old airspeed indicator too if you have one.

 

[Domenick]

First, it's unusual for a mechanical OEM tach to read high. Generally, after a few decades, they read about 100 rpm low at cruise.

I would get your tach checked. You can probably borrow a handheld tach. 3000 RPM is high. Either the tach is off or the aircraft is poorly propped. Regardless I would not exceed 2700 even during break in.

Or buy one of these for $36. They work from inside the cockpit. You can check the calibration by pointing at a fluorescent (not LED) light (they'll read 3600). Check your tach at various RPMs and make a conversion table.
https://www.amazon.com/dp/B0006N72U2/

 

[Gary Ward]

I would get your tach checked. You can probably borrow a handheld tach. 3000 RPM is high. Either the tach is off or the aircraft is poorly propped. Regardless I would not exceed 2700 even during break in.

Or you could get your propeller balanced and compare tach readings.

 

[Unit74]

Are those the original plugs out of a 1946 J3 Cub?

 

[mandm]

Would you really run your engine full power in cruise during break-in? I have been doing 75%, my mechanic told me to avoid touch and goes but other than that to fly it like I would normally. It has been using about 1 quart per 8 hours tach, the dipstick was loose but I might have lost some oil on one flight (my fault). But when you put too much oil it does blow out on the cowling under the landing light and on the nose wheel, 6 quarts is probably enough. The previous owner told me he uses 1 quart per 10 hours.

 

[Dan Thomas]

Would you really run your engine full power in cruise during break-in?

From Lycoming's break-in instructions:


That means 100% power, or as close as you can get to it. Even at full throttle and 5000 feet you won't get much more than 80% power, at redline RPM, for a normally-aspirated engine. You'd need to be near sea level to get anywhere near 100%.

https://www.lycoming.com/sites/defa...ating engine Break-In and Oil Consumption.pdf

 

[mandm]

Ok step 8 so that is something you do once oil consumption stabilizes?

 

[Dan Thomas]

Ok step 8 so that is something you do once oil consumption stabilizes?

No. It's all part of that first flight. I did it on the engines we replaced in the flight school airplanes, and we had very low oil consumption for the rest of the life of the engine. Maybe, at most, two quarts in 50 hours.

 

[mandm]

No. It's all part of that first flight. I did it on the engines we replaced in the flight school airplanes, and we had very low oil consumption for the rest of the life of the engine. Maybe, at most, two quarts in 50 hours.

Ok I know the mechanic did two flights and he said it was pretty much ready to go and to avoid touch & goes.

 

[Magman]

Avoiding excessive ground running during break-in is essential in my boo. Check trim setting, fuel selector etc BEFORE starting engine.
Long downwind taxi means ZERO cooling. A little planning here can minimize issues.

 

[Gary Ward]

Are those the original plugs out of a 1946 J3 Cub?

lol
They look like it!
They were out of a 1980 motor that flew 10 hrs in 10 years. They had low hrs on them but were rusty, I

bead blasted them clean and gave them a repaint. Flew them for about 500 hrs and then gave them to my AP and he put them in his brothers plane and I believe they are still flying today.

Good as new. almost.

 

[Dan Thomas]

lol
They look like it!
They were out of a 1980 motor that flew 10 hrs in 10 years. They had low hrs on them but were rusty, I

bead blasted them clean and gave them a repaint. Flew them for about 500 hrs and then gave them to my AP and he put them in his brothers plane and I believe they are still flying today.

Good as new. almost.

Are those Auburns? Auburn was a phenomenally good plug. Must be at least 15 years ago that Champion bought them up and shut them down. Big mistake. Auburn had the molded-in resistor that never failed, never gave trouble. Champion had that stupid spring-loaded resistor that made their plugs really poor. Enough of us complained long and loudly enough that Champion finally incorporated the molded-in resistor. They were likely losing business to Tempest, too, and Unison before that, both of which have the molded-in resistor.

Champion has a one-year warranty on their plugs, unless they have been run past the recommended replacement time, which I can't find in their literature. Auburn's warranty was 400 hours. I got 800 hours out of them, typically. Their electrodes eroded more slowly. Never got 800 hours out of any Champion.

 

[Silvaire]

First, it's unusual for a mechanical OEM tach to read high. Generally, after a few decades, they read about 100 rpm low at cruise.

Not that unusual, mine failed reading high. I think it had been reading high for quite a while before it really went south because when I put in the new one I gained 5 knots.

 

[Dan Thomas]

Not that unusual, mine failed reading high. I think it had been reading high for quite a while before it really went south because when I put in the new one I gained 5 knots.

They will read high if the tiny bit of oil on the indicator needle's aft bearing stub, which fits into the forward end of the input shaft, goes dry and sticky. That sticky oil will pull the needle farther around and make it read high.

Most tachs read low as they age as the magnet inside them weakens.

 

[Domenick]

Dan, I found a previous tach post of yours so informative, it went into my archive. Here's the link. Thanks.
https://www.pilotsofamerica.com/community/threads/tachometer-reads-high.131043/#post-3055354