Oil in cylinder, other cylinder issues

I have a mid time (1000 SFNEW) IO-360 Lycoming engine.
Recently oil consumption has increased from about 1 quart/10 hours to
about 1 quart/ 5 hours. For a long time we've collected oil on the
bottom #1 plug but it seems like its worse now.

In addition, we've had high aluminum levels in our oil samples for
several years but now showing high iron and other harder metals.
Blackstone is saying that our oil sample indicates high blow by and
seems to show that a piston pin plug is now rubbing on the cylinder.

The oil filter is still showing only a small amount of metal. The IA
at the A&P school says the amount of metal in the filter is expected
for any midtime engine, not excessive. Since the last couple of
Blackstone reports have indicated the pin plug may now be rubbing on a
cylinder we've been doing a boroscope every 10-20 hours of flight.
However, the boroscope is still coming up with nothing (we have
Nitrite cylinders and the cross hatching still looks great).
Compressions were all very high (enough that the A&P is always a bit
suprised to see them so high all around for a midtime engine)

So, I'm wondering where I should go from here.

1) How can I tell if the oil from #1 is coming past the valves or the
rings?
2) Is there any reason to believe the oil in #1 cylinder and the oil
analysis issues are related?
3) Other than the oil usage in #1 I really have nothing to suggest one
cylinder over the other for making metal in the oil sample. Should I
just address the oil in the #1 cylinder and ignore the sample report
until there are other signs (filter, boroscope, etc)? Or, should I
just start pulling all cylinders (I'm told its about 10 hours of labor
per cylinder ) until I find a busted pin plug?
4) I spoke with Lycoming. Although they didn't have any suggestions on
how to determine which cylinder has the bad pin plug, they did mention
that if we find the issue before there is much scraping on the
cylinder we should be able to simply put the cylinder back on (and
avoid sending it to a cylinder shop, saving lots of $$$). So basically
the sooner I find this, the less expensive it will be (well, I guess
if I have to pull 4 cylinders before I find it, it might not be less
expensive).
5) If I find a pin plug broken what should I do? Several A&Ps have
told me that pin plugs just work loose on Lycoming engines and I
should just replace the busted one and forget it. Others have said I
should do something to the engine to prevent the next plug from
working loose (not sure what).

-Robert

Assuming for a minute that the oil analysis and the oil on #1 plug are
not related, Blackstone could be right and it could be another cylinder
that has the broken pin plug. Can't that scraping be found with a
bore-scope like you did on #1? You shouldn't have to pull the cylinders
for that check should you?

If none of the cylinders show evidence of scraping, then the steel has
to be coming from somewhere else doesn't it?

This is very interesting...


-----Original Message-----
From: Robert M. Gary ]
Posted At: Wednesday, May 23, 2007 10:09 AM
Posted To: rec.aviation.owning
Conversation: Oil in cylinder, other cylinder issues
Subject: Oil in cylinder, other cylinder issues

I have a mid time (1000 SFNEW) IO-360 Lycoming engine.
Recently oil consumption has increased from about 1 quart/10 hours to
about 1 quart/ 5 hours. For a long time we've collected oil on the
bottom #1 plug but it seems like its worse now.

In addition, we've had high aluminum levels in our oil samples for
several years but now showing high iron and other harder metals.
Blackstone is saying that our oil sample indicates high blow by and
seems to show that a piston pin plug is now rubbing on the cylinder.

The oil filter is still showing only a small amount of metal. The IA
at the A&P school says the amount of metal in the filter is expected
for any midtime engine, not excessive. Since the last couple of
Blackstone reports have indicated the pin plug may now be rubbing on a
cylinder we've been doing a boroscope every 10-20 hours of flight.
However, the boroscope is still coming up with nothing (we have
Nitrite cylinders and the cross hatching still looks great).
Compressions were all very high (enough that the A&P is always a bit
suprised to see them so high all around for a midtime engine)

So, I'm wondering where I should go from here.

1) How can I tell if the oil from #1 is coming past the valves or the
rings?
2) Is there any reason to believe the oil in #1 cylinder and the oil
analysis issues are related?
3) Other than the oil usage in #1 I really have nothing to suggest one
cylinder over the other for making metal in the oil sample. Should I
just address the oil in the #1 cylinder and ignore the sample report
until there are other signs (filter, boroscope, etc)? Or, should I
just start pulling all cylinders (I'm told its about 10 hours of labor
per cylinder ) until I find a busted pin plug?
4) I spoke with Lycoming. Although they didn't have any suggestions on
how to determine which cylinder has the bad pin plug, they did mention
that if we find the issue before there is much scraping on the
cylinder we should be able to simply put the cylinder back on (and
avoid sending it to a cylinder shop, saving lots of $$$). So basically
the sooner I find this, the less expensive it will be (well, I guess
if I have to pull 4 cylinders before I find it, it might not be less
expensive).
5) If I find a pin plug broken what should I do? Several A&Ps have
told me that pin plugs just work loose on Lycoming engines and I
should just replace the busted one and forget it. Others have said I
should do something to the engine to prevent the next plug from
working loose (not sure what).

-Robert

Are you using sythetic oil?

If yes, how many of those 1000 hours have you been running synthetic oil?

On May 23, 4:09 pm, john smith wrote:
Are you using sythetic oil?

If yes, how many of those 1000 hours have you been running synthetic oil?

I'm running Elite right now but I previously had always run Aeroshell
15w50

On 23 May 2007 08:09:20 -0700, "Robert M. Gary"
wrote:

I have a mid time (1000 SFNEW) IO-360 Lycoming engine.
Recently oil consumption has increased from about 1 quart/10 hours to
about 1 quart/ 5 hours. For a long time we've collected oil on the
bottom #1 plug but it seems like its worse now.

What is the pattern of oil consumption? How often do you change your
oil? Assuming a 50 hr change interval, a "loose" engine is going to
burn as much oil in the last 10 hours as it did in the first
40-typically.

In addition, we've had high aluminum levels in our oil samples for
several years but now showing high iron and other harder metals.
Blackstone is saying that our oil sample indicates high blow by and
seems to show that a piston pin plug is now rubbing on the cylinder.

Please bear in mind that one of the two piston pin plugs on each
piston pin is going to be in contact with the cylinder wall during
normal operations.

The piston pin "floats" in the small end of the rod and in the piston.
The piston pin plugs "float" in the piston pin bore in the piston.

If you can tell me why in some cases they "rub" harder on the cylinder
wall, you are ahead of Lycoming, they are still trying to figure it
out.

The oil filter is still showing only a small amount of metal. The IA
at the A&P school says the amount of metal in the filter is expected
for any midtime engine, not excessive. Since the last couple of
Blackstone reports have indicated the pin plug may now be rubbing on a
cylinder we've been doing a boroscope every 10-20 hours of flight.
However, the boroscope is still coming up with nothing (we have
Nitrite cylinders and the cross hatching still looks great).
Compressions were all very high (enough that the A&P is always a bit
suprised to see them so high all around for a midtime engine)

Again, the piston pin plug is a relatively soft alloy, it may transfer
to the cylinder wall like a crayon, but it is not going to disturb the
material of the cylinder wall.

So, I'm wondering where I should go from here.

1) How can I tell if the oil from #1 is coming past the valves or the
rings?

It is more likely to be coming from the valve guides at 1000 hours.

2) Is there any reason to believe the oil in #1 cylinder and the oil
analysis issues are related?

No idea. Only way to know for sure is to tear down the engine and
physically inspect all the components.

3) Other than the oil usage in #1 I really have nothing to suggest one
cylinder over the other for making metal in the oil sample. Should I
just address the oil in the #1 cylinder and ignore the sample report
until there are other signs (filter, boroscope, etc)? Or, should I
just start pulling all cylinders (I'm told its about 10 hours of labor
per cylinder ) until I find a busted pin plug?

Better than half of "typical" Lycoming engines will have excessive
valve guide clearance after 1000 hours of operation. Unless an
increase in oil consumption is noted, a "wet" plug is found, or the
e-valve starts leaking, it is not a notable occurence. Heard of the
"wobble test"?

4) I spoke with Lycoming. Although they didn't have any suggestions on
how to determine which cylinder has the bad pin plug, they did mention
that if we find the issue before there is much scraping on the
cylinder we should be able to simply put the cylinder back on (and
avoid sending it to a cylinder shop, saving lots of $$$). So basically
the sooner I find this, the less expensive it will be (well, I guess
if I have to pull 4 cylinders before I find it, it might not be less
expensive).

Lycoming has a history of telling people that you can slide a cylinder
off and on and "save money". Speaking from personal experience, if you
remove a cylinder partially, and re-use it without a hone job and a
new ring set, it is likely to pump oil (increased blow-by). You will
have disturbed the working relationship between the rings and the
cylinder wall, and in-service rings often "sack" or loose some of the
spring tension that hold them "out" against the cylinder.

Not sure how gambling on another R/R, where you will be doing the job
properly (hone & ring set) is "less inexpensive". On most engine
installations, getting all the garbage out of the way (and putting it
all back on) is a much larger share of the labor cost than the actual
cylinder R/Repair.

5) If I find a pin plug broken what should I do? Several A&Ps have
told me that pin plugs just work loose on Lycoming engines and I
should just replace the busted one and forget it. Others have said I
should do something to the engine to prevent the next plug from
working loose (not sure what).

There is nothing to "work loose". There are two types of pin plugs in
service. One locates on the piston pin bore in the piston, the other
locates on the inner "hollow" in the piston pin itself. They can wear
slightly and be "loose", but show no other signs/symptoms, and have no
real affect on engine performance/engine life. They also can in
service begin to rub excessively on the cylinder wall, with no other
apparent faults. They can have the radiused end that butt into the
cylinder wall worn flat, and still not be "loose" in either the piston
or pin bore.

Piston pin metal is relatively easily identified in this case by hairs
in the suction screen or oil filter element.

TC

Maybe there's something funny going on in the connecting rod small end
bushing - like maybe the bushing is also floating in the con rod
bore? The presence of (hard?) iron in the analysis is bothersome.

On May 23, 8:09 am, "Robert M. Gary" wrote:
I have a mid time (1000 SFNEW) IO-360 Lycoming engine.
Recently oil consumption has increased from about 1 quart/10 hours to
about 1 quart/ 5 hours. For a long time we've collected oil on the
bottom #1 plug but it seems like its worse now.



Robert,
Oil is cheap compared to finding the problem, however if I was
wearing your sneakers.........
I'd say you have a broken oil control ring on that cylinder. It will
still show good compression, but just burns more oil. I would pull
that jug and inspect it.
option 1 $: put a new oil control ring and go fly
option 2 $$: hone it and re-ring the piston, If the piston is messed
up from the broken ring, replace it as well.
option 3 $$$$: bebuild that jug.

In regards to the piston plug idea. all you know is that you have had
some alumimun in your oil, and now some iron, and a lab "thinks" it
might be a piston plug.
however It might be an oil control ring eating it's ring grove. It
might be a small bur in your oil pump eating the oil pump housing. it
might be one of many things.

On May 24, 4:03 am, wrote:
On 23 May 2007 08:09:20 -0700, "Robert M. Gary"
wrote:
Please bear in mind that one of the two piston pin plugs on each
piston pin is going to be in contact with the cylinder wall during
normal operations.

The lab analysis is relative. They show my AL vs. other IO-360's and
mine has been 2-10 times higher than all others for the last 3 years.


Again, the piston pin plug is a relatively soft alloy, it may transfer
to the cylinder wall like a crayon, but it is not going to disturb the
material of the cylinder wall.

That's why I ignored the issue for the first 3 year. Now that we're
making harder metals the thinking is that pin plug is gone and harder
metals are rubbing.

-Robert

On May 24, 3:38 pm, "Robert M. Gary" wrote:
On May 24, 4:03 am, wrote:

On 23 May 2007 08:09:20 -0700, "Robert M. Gary"
wrote:
Please bear in mind that one of the two piston pin plugs on each
piston pin is going to be in contact with the cylinder wall during
normal operations.

The lab analysis is relative. They show my AL vs. other IO-360's and
mine has been 2-10 times higher than all others for the last 3 years.

Again, the piston pin plug is a relatively soft alloy, it may transfer
to the cylinder wall like a crayon, but it is not going to disturb the
material of the cylinder wall.

The pins wear when the rings leave a ridge in the cylinder
wall at the bottom of their travel. In engines that do not have rings
beneath the pison pin as well as above it, the pin plugs ride over the
ridge and get shaved, creating those aluminum hairs you see in the
filter. If an engine has rings below the pin, the ridge will be below
the pin plug's travel and it won't get shaved.
The ridge will form much quicker on engines that run too cold
or get flown too little. The blowby gases contain water vapour, which
condenses in the case and can also form on cooler parts of the
cylinder walls, such as those exposed to the incoming cooling air.
Corrosion forms wherever moisture collects, and a corroded cylinder
wall will wear at an astonishing rate and will form a ridge more
quickly. So now we have aluminum AND iron in the oil analysis.
We've had this trouble with an O-235 that just runs way too
cold, even in summer. The oil temp seldom gets far of the peg, and in
the winter it won't warm up much at all, even with the cooler blocked
off. I was able to isolate the bad cylinder with a sharpened piece of
welding rod, feeling the cylinder walls and finding the roughness, but
ended up taking them all off anyway. The danger with an ignored
failing pin plug is that it can end up rattling around in there and
jamming things, or leave altogether and rip up the piston or let the
pin end take the cylinder wall apart.
Bronze pins are available for some engines. They're more
resistant to the shaving, but the engine still has to come apart and
the cylinders fixed up. It's false economy to let it go.

Dan