Top Overhaul of Not?

[irishpilot]

I had a very similar issue. I decided the blowby was worth the top end overhaul. I am very happy with my decision. I turned wrenches for 30 hours, time towards my A&P, got to know the plane and my maintenance crew. The plane now burns 1 qt every 25 hours. The question really is, do you trust your engine at night or IFR or with your family? If the answer is no, then I think you have your answer.

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[PaulB]

16 hours ago, irishpilot said:

I had a very similar issue. I decided the blowby was worth the top end overhaul. I am very happy with my decision. I turned wrenches for 30 hours, time towards my A&P, got to know the plane and my maintenance crew. The plane now burns 1 qt every 25 hours. The question really is, do you trust your engine at night or IFR or with your family? If the answer is no, then I think you have your answer.

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Does excess blowby result in a lot of engine failures?

[DXB]

This seems like a complex issue for sure.  A quart every 5 hrs from blow by sounds to me like it's regarded as "safe" by any published manufacturer guideline. But I guess it might matter if the oil loss is relatively uniform across the rings of all cylinders (this sounds like no big deal at all), or most of it is from one cylinder while the others are tight. What is the worst that could happen in the latter situation?  Losing that cylinder entirely in flight?

 Then there is the issue of compression testing having adequate sensitivity to pick up the offender - per my understanding, the test is a static pressure measurement at TDC whereas a running engine (where the oil is actually coming past the rings) is much more dynamic in terms of pressure, temperature, and piston position.  Mike Busch almost seems to dismiss compression testing entirely - framing it an FAA requirement that has minimal real world value unless the leak past the rings is enormous, and also states that engines with high oil consumption can be perfectly airworthy.  I've found his online writings and EAA seminars wonderfully educational, but don't know whether to view such statements as uniquely wise or just being a contrarian against prevailing practices for it's own sake.

Unlike others here, I am not an A&P, just an inexperienced and fidgety owner who annoys the snot out of his A&Ps by obsessing over every little thing...

[irishpilot]

n

Does excess blowby result in a lot of engine failures?

Not necessarily. Combined with other factors it builds a picture of the engine's overall health. The first thing I'd do is call Blackstone and give them the tail number and see what oil analysis is on file, plus send in some oil to see the current numbers. When I did that, I found a high content of iron which suggested rust on the cylinder walls. If you have excessive blowby, with an oil analysis that shows high copper content and iron, you could be looking at an engine which has worn main bearings (copper) and rust from sitting (iron).

As far as excessive blowby is concerned, it is an issue that will only get worse with time. Realize that it can foul out spark plugs and it lowers your overall power. My engine had a high oil consumption and I continued to fly it until I lost a cylinder due to fouled plugs. If you haven't had the pleasure of flying on three cylinders, it is not something I'd like to deal with in IMC.

I disagree that compression checks are not worthwhile. Bad rings or bad cylinder walls will directly affect a static compression check.

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[jetdriven]

7 hours ago, DXB said:

This seems like a complex issue for sure.  A quart every 5 hrs from blow by sounds to me like it's regarded as "safe" by any published manufacturer guideline. But I guess it might matter if the oil loss is relatively uniform across the rings of all cylinders (this sounds like no big deal at all), or most of it is from one cylinder while the others are tight. What is the worst that could happen in the latter situation?  Losing that cylinder entirely in flight?

 Then there is the issue of compression testing having adequate sensitivity to pick up the offender - per my understanding, the test is a static pressure measurement at TDC whereas a running engine (where the oil is actually coming past the rings) is much more dynamic in terms of pressure, temperature, and piston position.  Mike Busch almost seems to dismiss compression testing entirely - framing it an FAA requirement that has minimal real world value unless the leak past the rings is enormous, and also states that engines with high oil consumption can be perfectly airworthy.  I've found his online writings and EAA seminars wonderfully educational, but don't know whether to view such statements as uniquely wise or just being a contrarian against prevailing practices for it's own sake.

Unlike others here, I am not an A&P, just an inexperienced and fidgety owner who annoys the snot out of his A&Ps by obsessing over every little thing...

My 400 hour factory Lycoming IO360 goes through a quart every 6-8 hours, and had since it was installed.

[ryoder]

Go for it.  Christina did it.  

 

[Bob - S50]

Thanks all for the input.  Sounds to be about evenly split.

We have an oil analysis done every oil change, except we use AvLab rather than Blackstone.  All of our metals are within the normal range.  All of them are below the average readings except Iron and chromium.  However, iron levels have been climbing.  Once we wore the 10 years of inactivity off it, iron was around 15 ppm for 5 oil changes.  Then it increased to about 25 for one change and has been just over 40 for that last 3.  However, that's also about the time we finally figured out how to start a hot engine and changed our procedures a little.  Iron is holding steady in the low 40's now.  We will be due for another oil change in a few weeks.  What we usually do is buy a case of oil at oil change.  We add 6 quarts and Camguard at the change and once we have added the last quart and are nearing needing another one, we change the oil.  Usually get around 30 to 40 hours before that happens.  And yes, every time we add oil we add 1.5 oz of Camguard.

Used to be if we had more than 6 quarts on board it would toss everything over 6.  When we switched to the Phillips (could be a coincidence) 5 seems to be the new 6.  If we fill to 6 it gets down to a bit over 5 pretty quickly then seems to stay there.

I'm inclined to get the top done but have to convince my 3 partners.  I'll ask our mechanic what he thinks.  If he says it would be a good idea then the partners will probably go along.

[DXB]

1 hour ago, Bob - S50 said:

We have an oil analysis done every oil change, except we use AvLab rather than Blackstone.  All of our metals are within the normal range.  All of them are below the average readings except Iron and chromium.  However, iron levels have been climbing.  Once we wore the 10 years of inactivity off it, iron was around 15 ppm for 5 oil changes.  Then it increased to about 25 for one change and has been just over 40 for that last 3.  However, that's also about the time we finally figured out how to start a hot engine and changed our procedures a little.  Iron is holding steady in the low 40's now.  We will be due for another oil change in a few weeks. 

The metal assays in oil analysis seem incredibly sensitive - I  question if any meaningful conclusion can be drawn about the health of an engine by monitoring an iron trend from 25 to 40.  So far in my (admittedly limited) ownership history, I've perceived minimal value added in routine oil analysis at every oil change. I continue to send it dutifully, acknowledging I have more to learn here. But seeing every blip in iron and chromium if the plane sits for a bit has only been a source of worry that has led to no concrete action I can see contributing to safety. It may provide a data point that corroborates other findings in the engine (oil consumption, metal in the filter/screen, borescope findings, engine monitor data), but it seems a dispensable one - abnormalities in isolation on oil analysis merit no concrete action, and the absence of them in context of other findings provides very little security.

I pose these questions to A&Ps and experienced owners at every opportunity, and I have as yet to hear a compelling case for oil analysis from anyone. Certainly there are some very respected mechanics who feel it's of minimal value, and many who who believe in it but can't articulate a strong rationale.

Not trying to stir things up for its own sake -  that would involve talking smack about Camguard...

[PaulB]

56 minutes ago, DXB said:

The metal assays in oil analysis seem incredibly sensitive - I  question if any meaningful conclusion can be drawn about the health of an engine by monitoring an iron trend from 25 to 40.  So far in my (admittedly limited) ownership history, I've perceived minimal value added in routine oil analysis at every oil change. I continue to send it dutifully, acknowledging I have more to learn here. But seeing every blip in iron and chromium if the plane sits for a bit has only been a source of worry that has led to no concrete action I can see contributing to safety. It may provide a data point that corroborates other findings in the engine (oil consumption, metal in the filter/screen, borescope findings, engine monitor data), but it seems a dispensable one - abnormalities in isolation on oil analysis merit no concrete action, and the absence of them in context of other findings provides very little security.

My take on it is similar to yours. I do it with every change becuase it's cheap and it's more info but I'm not going to react to a single out of whack value. My though is to use it to monitor the trend and then back it up with other pieces of information before pulling the trigger on maintainence. 

[irishpilot]

Oil analysis is a trend indicator. If you have metals that continue to climb or spike it is telling you something. If an engine starts making metal (copper, iron, zinc, etc) there is something wrong. Just ask any engine mechanic what the oil shows when an engine spins a bearing or a cam lobe flattens.

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[DXB]

7 minutes ago, irishpilot said:

Oil analysis is a trend indicator. If you have metals that continue to climb or spike it is telling you something. If an engine starts making metal (copper, iron, zinc, etc) there is something wrong. Just ask any engine mechanic what the oil shows when an engine spins a bearing or a cam lobe flattens.

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A flattened cam lobe produces obvious  visible metal in the filter and causes only subtle power decrement, not catastrophic failure.  A spun bearing can indeed be catastrophic but is usually an infant mortality issue or results from oil starvation.  I still fail to perceive the value added from routine oil analysis (though I keep doing it).  Not a contrarian- my mind can be changed...

[jetdriven]

On April 25, 2016 at 5:40 PM, PaulB said:

I'm no expert but that's what Mike Busch says.

A a bad lifter which kills the cam lobe can be seen as a steady trend from <20 PPM iron in the oil analysis to 30, then 60, then 100 PPM. You can see this, even before the cam loses significant lift. But the Internet of full of pilots who had a surprise cam lobe failure.  "What did the oil analysis say leading up to this?"  And, always, the answer was "we didn't do oil analysis."

 

 

[DXB]

11 minutes ago, jetdriven said:

A a bad lifter which kills the cam lobe can be seen as a steady trend from <20 PPM iron in the oil analysis to 30, then 60, then 100 PPM. You can see this, even before the cam loses significant lift. But the Internet of full of pilots who had a surprise cam lobe failure.  "What did the oil analysis say leading up to this?"  And, always, the answer was "we didn't do oil analysis."

But are those rapidly flattening cam lobe surprises killing anyone?  And aren't they apparent in the filter, if one chooses to look?  And without gross metal in the filter, would anyone ever pull a jug to find it? If not, what difference is oil analysis making here?

[DonMuncy]

26 minutes ago, DXB said:

 I still fail to perceive the value added from routine oil analysis (though I keep doing it).  Not a contrarian- my mind can be changed...

Think of it like buying insurance. If you never need it, it was a waste of money. You hope you will never need the oil analysis,, and many people fly a long time without suffering at all because of it. BUT, if you start seeing things in the analysis report, odds are good you can stop and fix things before a catastrophic failure.

[DXB]

Just now, DonMuncy said:

Think of it like buying insurance. If you never need it, it was a waste of money. You hope you will never need the oil analysis,, and many people fly a long time without suffering at all because of it. BUT, if you start seeing things in the analysis report, odds are good you can stop and fix things before a catastrophic failure.

Don - can you give me a concrete example of how oil analysis can prevent a catastrophic failure that would not have given other clear warning signs?   

[MB65E]

It won't prevent an engine failure. Nor will the lab tell you anything is really wrong if the trends are the same or only increacing slightly. 

Monitoring Iron should be the priority. 

I once had an engine go steady from 26ppm iron, to 36, to 50, then 60ppm. Finally, the Cam was flat on 2 cylinders.  AV Labs never pinged an alert and unless you had the prior sheet, you'd really never knew what you were looking at. Not they trend the last 3 samples on the same sheet. 

Now from others data I know something is going on at 40ppm and will start looking for where it is coming from. 

Just a single data point for others.

-Matt

[Guest]

5 hours ago, MB65E said:

It won't prevent an engine failure. Nor will the lab tell you anything is really wrong if the trends are the same or only increacing slightly. 

Monitoring Iron should be the priority. 

I once had an engine go steady from 26ppm iron, to 36, to 50, then 60ppm. Finally, the Cam was flat on 2 cylinders.  AV Labs never pinged an alert and unless you had the prior sheet, you'd really never knew what you were looking at. Not they trend the last 3 samples on the same sheet. 

Now from others data I know something is going on at 40ppm and will start looking for where it is coming from. 

Just a single data point for others.

-Matt

In my experience, I've had oil sampling come back with perfect results when I have a magnet full of cam and lifters in my hand.  Not all labs are created equal and not all are accredited.

We just did a PPI on a Piper Mirage, the oil sample raised concerns of higher iron.  We asked how did it compare to Lycoming's values?  "They don't publish limits" we were told, BS its in an SI if you care to look.  

Another thing to understand is that labs use the average numbers from their own sampling, if they only do a few of your engine type the data will be less accurate than from a lab with a larger pool of engines.

Clarence

 

[Yooper Rocketman]

21 hours ago, DXB said:

I pose these questions to A&Ps and experienced owners at every opportunity, and I have as yet to hear a compelling case for oil analysis from anyone. Certainly there are some very respected mechanics who feel it's of minimal value, and many who who believe in it but can't articulate a strong rationale.

 

I sent out oil samples on my F model after every oil change, especially after I went over TBO.  I found a handful of metal in my filter during a routine oil change at exactly 2400 hours.  I wrenched on big trucks all my life, doing mostly engine, transmission and differential overhauls, ( in addition to building drag racing engines), so felt pretty comfortable working with oil samples.  Anyway, I decided to send an oil sample off of the oil on my F model that had just breathed it's last.  The sample came back with nothing in it to give me concern had I not found the handful of metal in the filter, and I had 500 hours of trends (25 hour oil changes) to compare it with.

I'm not a big fan of oil samples.  I do them occasionally now, but I don't expect they will warn me of anything I haven't already discovered from other signs already.

Tom

[jetdriven]

the oil sample reads miscroscopic wear metals, not big pieces.  An engine shedding big pieces wont trigger oil analysis necessarily, but slow even wear gets picked up. Like when I had a cracked intake plenum and it was admitting dust, silicon, iron and aluminum all were slightly elevated. Taking the airbox off, I found the crack.

[ArtVandelay]

There is big chunks that won't make it past the pickup screen, you look for these in the drained oil, small chunks that won't make past the oil filter, and very fine that circulate in the oil. I personally don't test every oil change, i do every other one (i do about 6 oil changes a year), it does make me feel like I'm being proactive, but I'm in the "do I need this" camp since it only seems to show normal wear, you might see normal wear even if you cam,crank shafts were way out of spec.

[Godfather]

1 hour ago, Yooper Rocketman said:

I sent out oil samples on my F model after every oil change, especially after I went over TBO.  I found a handful of metal in my filter during a routine oil change at exactly 2400 hours.  I wrenched on big trucks all my life, doing mostly engine, transmission and differential overhauls, ( in addition to building drag racing engines), so felt pretty comfortable working with oil samples.  Anyway, I decided to send an oil sample off of the oil on my F model that had just breathed it's last.  The sample came back with nothing in it to give me concern had I not found the handful of metal in the filter, and I had 500 hours of trends (25 hour oil changes) to compare it with.

I'm not a big fan of oil samples.  I do them occasionally now, but I don't expect they will warn me of anything I haven't already discovered from other signs already.

Tom

Just curious if you ended up overhauling the engine or continued to push on?

[DXB]

1 hour ago, jetdriven said:

the oil sample reads miscroscopic wear metals, not big pieces.  An engine shedding big pieces wont trigger oil analysis necessarily, but slow even wear gets picked up. Like when I had a cracked intake plenum and it was admitting dust, silicon, iron and aluminum all were slightly elevated. Taking the airbox off, I found the crack.

Detecting leaks in the intake does seem like legit value added from oil analysis -  this is also the only concrete example that I've seen cited by Mike Busch as to how it helps.  

Funny story related to that - when I first was learing to do oil changes right after I bought my plane, I liberally slathered that Dow Corning silicon grease all over the filter gasket before installing. Don't do that.  The next oil analysis came back with sky high silicon and had me wigging out about an intake leak...until someone asked me how I install my filter.  

[jlunseth]

Well, there is plenty of pressure in the crankcase.  The pressure source is the engine itself.  The rings don't seal perfectly and there is always some blow by.  That is what the breather is for, to vent off pressure.  I can say for a fact there is enough to blow oil out because I have had it happen twice in fairly dramatic fashion from two different causes.  One was a quick drain that had swallowed a tiny piece of plastic and did not completely seal.  When the engine was operated (over Lake Mich then over Canada) we blew most of the oil out (4 qts. in a couple of hours).  The other was the air/oil separator freezing up during the winter.  The breather is run through the separator.  When the separator became blocked the engine blew oil out every available orifice, big streaks down both sides of the fuselage.  

Oil leaks are not always easy to find, and there are circumstances where the leakage occurs only when the engine is pressurized/operated.  I had the quick drain checked by a mechanic right before the fateful flight, because there was a one-drop drip on the tire, and was told not to worry, that was normal for quick drains.  

I can also tell you those "tiny" leaks that are hard to find, and especially the ones that blow when pressurized, throw out alot of oil.  I was going through about a quart an hour and thinking a top was coming soon when we discovered that quick drain.  Now I go from one oil change to another adding just 0 to 1 quart.  If the mechanic fills to 8 at the oil change and I bring it in 50 hours later it will be at 6.  And that is a Conti.

[DonMuncy]

11 hours ago, DXB said:

Don - can you give me a concrete example of how oil analysis can prevent a catastrophic failure that would not have given other clear warning signs?   

No, I can't. In almost all cases, you would get some other indication as well, and likely in time to prevent the massive failure. You may be able to pick it up earlier with the oil analysis. If you had to make a choice, cutting and inspecting the filter is more important. But I believe you increase your odds a little by doing both.

Your engine, your money, your choice.

[DXB]

9 minutes ago, jlunseth said:

Well, there is plenty of pressure in the crankcase.  The pressure source is the engine itself.  The rings don't seal perfectly and there is always some blow by.  That is what the breather is for, to vent off pressure.  I can say for a fact there is enough to blow oil out because I have had it happen twice in fairly dramatic fashion from two different causes.  One was a quick drain that had swallowed a tiny piece of plastic and did not completely seal.  When the engine was operated (over Lake Mich then over Canada) we blew most of the oil out (4 qts. in a couple of hours).  The other was the air/oil separator freezing up during the winter.  The breather is run through the separator.  When the separator became blocked the engine blew oil out every available orifice, big streaks down both sides of the fuselage.  

Oil leaks are not always easy to find, and there are circumstances where the leakage occurs only when the engine is pressurized/operated.  I had the quick drain checked by a mechanic right before the fateful flight, because there was a one-drop drip on the tire, and was told not to worry, that was normal for quick drains.  

I can also tell you those "tiny" leaks that are hard to find, and especially the ones that blow when pressurized, throw out alot of oil.  I was going through about a quart an hour and thinking a top was coming soon when we discovered that quick drain.  Now I go from one oil change to another adding just 0 to 1 quart.  If the mechanic fills to 8 at the oil change and I bring it in 50 hours later it will be at 6.  And that is a Conti.

This is interesting.  My quick drain is the most oily thing under my cowl- I wipe off periodically but it always gets damp with oil, even above the tip.  But there's never any hint of oil on the cowl flap below or anywhere else in the cowl, so I figure no big deal.  But I wonder if it only leaks at high power when the case gets pressurized, and the stuff all blows out from the cowl flap opening and never touches anything else. Seems a little far fetched but your description above made me wonder.