Mystery Oil leak... cont'd and long

Why would a cold engine drip oil out of the breather? If you're bored or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil leak on
one of our engines. Nothing severe, not enough to show up as "missing" on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out, so I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on our #3
cylinder. Nearly impossible to get my hands on with the bottom cowl in
place, I tightened it up as much as I could without replacing the hose
clamp. Occasionally notice a drop of oil hanging from the bottom of the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle body in a
valley where the throttle body moves upward to connect to the air intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as single
drops can be found on the bottom of collection points such as bolt heads and
flanges. The floor of the bottom cowl never has any streaks, streams, or
oil lines but is generally covered with a very thin coat of oil that returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell W100.
Never displacing an amount that was observable as a loss on the dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we fill
them up to 12 quarts. If we leave them down around 10 quarts, they can go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from W100 to
15W-50. We've flown about 10 hours on this oil change so far, but this is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the floor
directly under the breather tube the day AFTER as short 30 minute flight.
The plane came out of a heated hanger and was completely warm and toasty, I
flew it home, tucked it away, no drips or drops as I left our old unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and everything
seemed as described above (a few drops hanging here and there, oil along the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't flown,
engines not started, but it dripped another 2 tablespoons full of oil out of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the oil on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil out of
the breather? Especially the day AFTER it was flown? I can understand if
there was pressure remaining in the sump there may be some spit out the
breather, but after 24 hours, I can't believe there would be any pressure in
the sump.

Second thought, which I've been told Lycoming's don't have a problem with,
would be a leaking intake valve guide. Could that be seeping oil back down
through the intake and somehow make it to the throttle body? One of the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes up
towards the back of the accessory case, towards the oil pump I believe, I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim

Is is possible that it just takes a lot longer for the oil to exit the
breather tube in cold weather because it is thicker due to the lower
temperatures?

Mike
MU-2


"Jim Burns" wrote in message
...
Why would a cold engine drip oil out of the breather? If you're bored or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil leak
on
one of our engines. Nothing severe, not enough to show up as "missing" on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out, so
I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on our #3
cylinder. Nearly impossible to get my hands on with the bottom cowl in
place, I tightened it up as much as I could without replacing the hose
clamp. Occasionally notice a drop of oil hanging from the bottom of the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle body in
a
valley where the throttle body moves upward to connect to the air intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as single
drops can be found on the bottom of collection points such as bolt heads
and
flanges. The floor of the bottom cowl never has any streaks, streams, or
oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell W100.
Never displacing an amount that was observable as a loss on the dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we fill
them up to 12 quarts. If we leave them down around 10 quarts, they can go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from W100 to
15W-50. We've flown about 10 hours on this oil change so far, but this is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the floor
directly under the breather tube the day AFTER as short 30 minute flight.
The plane came out of a heated hanger and was completely warm and toasty,
I
flew it home, tucked it away, no drips or drops as I left our old unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and everything
seemed as described above (a few drops hanging here and there, oil along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil out
of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the oil on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil out
of
the breather? Especially the day AFTER it was flown? I can understand if
there was pressure remaining in the sump there may be some spit out the
breather, but after 24 hours, I can't believe there would be any pressure
in
the sump.

Second thought, which I've been told Lycoming's don't have a problem with,
would be a leaking intake valve guide. Could that be seeping oil back
down
through the intake and somehow make it to the throttle body? One of the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes up
towards the back of the accessory case, towards the oil pump I believe, I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim

Very possible, but why would one engine do it and not the other?

Jim

"Mike Rapoport" wrote in message
k.net...
Is is possible that it just takes a lot longer for the oil to exit the
breather tube in cold weather because it is thicker due to the lower
temperatures?

Mike
MU-2


"Jim Burns" wrote in message
...
Why would a cold engine drip oil out of the breather? If you're bored
or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil leak
on
one of our engines. Nothing severe, not enough to show up as "missing"
on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out, so
I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on our
#3
cylinder. Nearly impossible to get my hands on with the bottom cowl in
place, I tightened it up as much as I could without replacing the hose
clamp. Occasionally notice a drop of oil hanging from the bottom of the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle body
in
a
valley where the throttle body moves upward to connect to the air intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as
single
drops can be found on the bottom of collection points such as bolt heads
and
flanges. The floor of the bottom cowl never has any streaks, streams,
or
oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell
W100.
Never displacing an amount that was observable as a loss on the
dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we
fill
them up to 12 quarts. If we leave them down around 10 quarts, they can
go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from W100
to
15W-50. We've flown about 10 hours on this oil change so far, but this
is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the floor
directly under the breather tube the day AFTER as short 30 minute
flight.
The plane came out of a heated hanger and was completely warm and
toasty,
I
flew it home, tucked it away, no drips or drops as I left our old
unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and
everything
seemed as described above (a few drops hanging here and there, oil along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil
out
of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the oil
on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil out
of
the breather? Especially the day AFTER it was flown? I can understand
if
there was pressure remaining in the sump there may be some spit out the
breather, but after 24 hours, I can't believe there would be any
pressure
in
the sump.

Second thought, which I've been told Lycoming's don't have a problem
with,
would be a leaking intake valve guide. Could that be seeping oil back
down
through the intake and somehow make it to the throttle body? One of the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes up
towards the back of the accessory case, towards the oil pump I believe,
I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim

Perhaps the other engine doesn't send as much oil out the breather, or
perhaps it is out of oil. No idea really, it was just a thought. Try
switching the engines side to side.

Mike
MU-2



"Jim Burns" wrote in message
news
Very possible, but why would one engine do it and not the other?

Jim

"Mike Rapoport" wrote in message
k.net...
Is is possible that it just takes a lot longer for the oil to exit the
breather tube in cold weather because it is thicker due to the lower
temperatures?

Mike
MU-2


"Jim Burns" wrote in message
...
Why would a cold engine drip oil out of the breather? If you're bored
or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil
leak
on
one of our engines. Nothing severe, not enough to show up as "missing"
on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out, so
I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on our
#3
cylinder. Nearly impossible to get my hands on with the bottom cowl in
place, I tightened it up as much as I could without replacing the hose
clamp. Occasionally notice a drop of oil hanging from the bottom of
the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle body
in
a
valley where the throttle body moves upward to connect to the air
intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as
single
drops can be found on the bottom of collection points such as bolt
heads
and
flanges. The floor of the bottom cowl never has any streaks, streams,
or
oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell
W100.
Never displacing an amount that was observable as a loss on the
dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we
fill
them up to 12 quarts. If we leave them down around 10 quarts, they can
go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from W100
to
15W-50. We've flown about 10 hours on this oil change so far, but this
is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the
floor
directly under the breather tube the day AFTER as short 30 minute
flight.
The plane came out of a heated hanger and was completely warm and
toasty,
I
flew it home, tucked it away, no drips or drops as I left our old
unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and
everything
seemed as described above (a few drops hanging here and there, oil
along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil
out
of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the oil
on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil
out
of
the breather? Especially the day AFTER it was flown? I can understand
if
there was pressure remaining in the sump there may be some spit out the
breather, but after 24 hours, I can't believe there would be any
pressure
in
the sump.

Second thought, which I've been told Lycoming's don't have a problem
with,
would be a leaking intake valve guide. Could that be seeping oil back
down
through the intake and somehow make it to the throttle body? One of
the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes up
towards the back of the accessory case, towards the oil pump I believe,
I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim

I think your first idea may be a posibility. leaky engine is 1800 hours
with 600 hour cylinders, dry engine is 600 hours.

The breather lines are small diameter, say 1/4", so I guess cold thick oil
would have a hard time flowing through them and may take several hours.

Jim

"Mike Rapoport" wrote in message
ink.net...
Perhaps the other engine doesn't send as much oil out the breather, or
perhaps it is out of oil. No idea really, it was just a thought. Try
switching the engines side to side.

Mike
MU-2



"Jim Burns" wrote in message
news
Very possible, but why would one engine do it and not the other?

Jim

"Mike Rapoport" wrote in message
k.net...
Is is possible that it just takes a lot longer for the oil to exit the
breather tube in cold weather because it is thicker due to the lower
temperatures?

Mike
MU-2


"Jim Burns" wrote in message
...
Why would a cold engine drip oil out of the breather? If you're
bored
or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil
leak
on
one of our engines. Nothing severe, not enough to show up as
"missing"
on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out,
so
I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on
our
#3
cylinder. Nearly impossible to get my hands on with the bottom cowl
in
place, I tightened it up as much as I could without replacing the
hose
clamp. Occasionally notice a drop of oil hanging from the bottom of
the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle
body
in
a
valley where the throttle body moves upward to connect to the air
intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as
single
drops can be found on the bottom of collection points such as bolt
heads
and
flanges. The floor of the bottom cowl never has any streaks,
streams,
or
oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell
W100.
Never displacing an amount that was observable as a loss on the
dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we
fill
them up to 12 quarts. If we leave them down around 10 quarts, they
can
go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from
W100
to
15W-50. We've flown about 10 hours on this oil change so far, but
this
is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the
floor
directly under the breather tube the day AFTER as short 30 minute
flight.
The plane came out of a heated hanger and was completely warm and
toasty,
I
flew it home, tucked it away, no drips or drops as I left our old
unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and
everything
seemed as described above (a few drops hanging here and there, oil
along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil
out
of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the
oil
on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil
out
of
the breather? Especially the day AFTER it was flown? I can
understand
if
there was pressure remaining in the sump there may be some spit out
the
breather, but after 24 hours, I can't believe there would be any
pressure
in
the sump.

Second thought, which I've been told Lycoming's don't have a problem
with,
would be a leaking intake valve guide. Could that be seeping oil
back
down
through the intake and somehow make it to the throttle body? One of
the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes
up
towards the back of the accessory case, towards the oil pump I
believe,
I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim

Jim Burns wrote:

I think your first idea may be a posibility. leaky engine is 1800 hours
with 600 hour cylinders, dry engine is 600 hours.

The breather lines are small diameter, say 1/4", so I guess cold thick oil
would have a hard time flowing through them and may take several hours.

Jim

"Mike Rapoport" wrote in message
ink.net...

Perhaps the other engine doesn't send as much oil out the breather, or
perhaps it is out of oil. No idea really, it was just a thought. Try
switching the engines side to side.

Mike
MU-2



"Jim Burns" wrote in message
news
Very possible, but why would one engine do it and not the other?

Jim

"Mike Rapoport" wrote in message
link.net...

Is is possible that it just takes a lot longer for the oil to exit the
breather tube in cold weather because it is thicker due to the lower
temperatures?

Mike
MU-2


"Jim Burns" wrote in message
...

Why would a cold engine drip oil out of the breather? If you're

bored

or

have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil
leak
on
one of our engines. Nothing severe, not enough to show up as

"missing"

on

the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out,

so

I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on

our

#3

cylinder. Nearly impossible to get my hands on with the bottom cowl

in

place, I tightened it up as much as I could without replacing the

hose

clamp. Occasionally notice a drop of oil hanging from the bottom of
the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle

body

in

a
valley where the throttle body moves upward to connect to the air
intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as

single

drops can be found on the bottom of collection points such as bolt
heads
and
flanges. The floor of the bottom cowl never has any streaks,

streams,

or

oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell

W100.

Never displacing an amount that was observable as a loss on the

dipstick.

Normally both engines use about a quart of oil every 6-8 hours if we

fill

them up to 12 quarts. If we leave them down around 10 quarts, they

can

go

up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from

W100

to

15W-50. We've flown about 10 hours on this oil change so far, but

this

is

what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the
floor
directly under the breather tube the day AFTER as short 30 minute

flight.

The plane came out of a heated hanger and was completely warm and

toasty,

I
flew it home, tucked it away, no drips or drops as I left our old

unheated

hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and

everything

seemed as described above (a few drops hanging here and there, oil
along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil

out

of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the

oil

on

the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil
out
of
the breather? Especially the day AFTER it was flown? I can

understand

if

there was pressure remaining in the sump there may be some spit out

the

breather, but after 24 hours, I can't believe there would be any

pressure

in
the sump.

Second thought, which I've been told Lycoming's don't have a problem

with,

would be a leaking intake valve guide. Could that be seeping oil

back

down
through the intake and somehow make it to the throttle body? One of
the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes

up

towards the back of the accessory case, towards the oil pump I

believe,

I

need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim








1/4" is a mighty small breather hose! Check to make sure it's correct!
Also, you might want to make sure the breather line is placed so that it
definitely and distinctly drains back towards the engine, with no low
spots to pool or collect oil in. If you get an oil "pocket" small
changes in temperature can cause the air in the crankcase to "puff" the
oil out of the low spot onto the floor, or wherever.

Rip

AH!! you are sooo correct! The 1/4" hose that is dripping the oil is the
air box drain hose, which exits just ahead of the breather hose (much
larger). Sooo now the mystery gets mysterious! Oil on top of the air box
collects from "where ever" several hours after a flight, seeps into the
airbox then slowly drains out the drain hose???

OR intake valve guide leaking down through the intake tube into the
airbox???

OR...????

Jim

"Rip" wrote in message
t...
1/4" is a mighty small breather hose! Check to make sure it's correct!
Also, you might want to make sure the breather line is placed so that it
definitely and distinctly drains back towards the engine, with no low
spots to pool or collect oil in. If you get an oil "pocket" small
changes in temperature can cause the air in the crankcase to "puff" the
oil out of the low spot onto the floor, or wherever.

Rip

OR intake valve guide leaking down through the intake tube into the
airbox???

OR...????

This is why a wise old grey-beard at the airport, upon hearing me bemoaning
the fact that I've got an oil drip AFTER installing an air/oil separator,
remarked: "There are over 100 places that can leak oil on an aircraft
engine. Your air/oil separator has addressed one of them -- and created
three more potential leaks..."

:-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Hi Jim,

I wondered if you ever found the source of the oil leak / drip
problem you were chasing?

The idea that this make be a drip out of the air box after oil
has seeped down from the top of the air box sounds reasonable.

Both engines on my Aztec leak and drip. If I ever went into
the hangar and did not find some oil under the engines, I'd
think someone had washed the floor within the last 30 minutes!

Seriously, we'd have lots of leaks on the oil return lines. The
little rubber hoses and associated hose clamps were a nightmare
to get leak-proof.

I was curious about your oil consumption. You stated you could
go 10 hours if filled to the 10 quart level. Our will not do that. At
10 quarts, each engine will be a quart low after a couple of hours.
At the 9 quart level, they will run for 4 to 5 hours before being a quart
low. I'm nervious about letting them get before 8 quarts, but I'm
wondering if they would run at the 8 quart level for a much longer
period of time. My Cessna 172 with its O320 sits happily for hours
on end at the 6 quarts level, while filling it up to its 8 quart capacity
results in losing 2 quarts in a few hours. Scaling this to the IO-540
with the 12 quart sump equates to 9 quarts being the 75% full point,
and I'd think that the level would be stable. But I don't see that on my
IO-540s.

Both engines are high time, but one has less than a 100 hours on all new
cylinders, yet both behave the same. This makes me think that the oil
loss is in the crankcase and is not being burned. Sounds like yours are
stable at 10 quarts. I guess we've more or better leaks than you. Let me
know if you need some :-)

Ronnie


"Jim Burns" wrote in message
...
Why would a cold engine drip oil out of the breather? If you're bored or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil leak
on
one of our engines. Nothing severe, not enough to show up as "missing" on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out, so
I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on our #3
cylinder. Nearly impossible to get my hands on with the bottom cowl in
place, I tightened it up as much as I could without replacing the hose
clamp. Occasionally notice a drop of oil hanging from the bottom of the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle body in
a
valley where the throttle body moves upward to connect to the air intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as single
drops can be found on the bottom of collection points such as bolt heads
and
flanges. The floor of the bottom cowl never has any streaks, streams, or
oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell W100.
Never displacing an amount that was observable as a loss on the dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we fill
them up to 12 quarts. If we leave them down around 10 quarts, they can go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from W100 to
15W-50. We've flown about 10 hours on this oil change so far, but this is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the floor
directly under the breather tube the day AFTER as short 30 minute flight.
The plane came out of a heated hanger and was completely warm and toasty,
I
flew it home, tucked it away, no drips or drops as I left our old unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and everything
seemed as described above (a few drops hanging here and there, oil along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil out
of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the oil on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil out
of
the breather? Especially the day AFTER it was flown? I can understand if
there was pressure remaining in the sump there may be some spit out the
breather, but after 24 hours, I can't believe there would be any pressure
in
the sump.

Second thought, which I've been told Lycoming's don't have a problem with,
would be a leaking intake valve guide. Could that be seeping oil back
down
through the intake and somehow make it to the throttle body? One of the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes up
towards the back of the accessory case, towards the oil pump I believe, I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim

When most of these engines were certified, the rule was a gallon of oil
for each 100 hp.
You shouldn't have a problem running down in the 4-6 quart range. It all
depends where the oil pickup is.
Every pickup I've seen would run oil in the 2-3 quart range without
problems.
With this, I'm still most comfortable in the 6-8 quart range. Its nice
to have that buffer zone of excess oil.


nobody wrote:
Hi Jim,

I wondered if you ever found the source of the oil leak / drip
problem you were chasing?

The idea that this make be a drip out of the air box after oil
has seeped down from the top of the air box sounds reasonable.

Both engines on my Aztec leak and drip. If I ever went into
the hangar and did not find some oil under the engines, I'd
think someone had washed the floor within the last 30 minutes!

Seriously, we'd have lots of leaks on the oil return lines. The
little rubber hoses and associated hose clamps were a nightmare
to get leak-proof.

I was curious about your oil consumption. You stated you could
go 10 hours if filled to the 10 quart level. Our will not do that. At
10 quarts, each engine will be a quart low after a couple of hours.
At the 9 quart level, they will run for 4 to 5 hours before being a quart
low. I'm nervious about letting them get before 8 quarts, but I'm
wondering if they would run at the 8 quart level for a much longer
period of time. My Cessna 172 with its O320 sits happily for hours
on end at the 6 quarts level, while filling it up to its 8 quart capacity
results in losing 2 quarts in a few hours. Scaling this to the IO-540
with the 12 quart sump equates to 9 quarts being the 75% full point,
and I'd think that the level would be stable. But I don't see that on my
IO-540s.

Both engines are high time, but one has less than a 100 hours on all new
cylinders, yet both behave the same. This makes me think that the oil
loss is in the crankcase and is not being burned. Sounds like yours are
stable at 10 quarts. I guess we've more or better leaks than you. Let me
know if you need some :-)

Ronnie


"Jim Burns" wrote in message
...

Why would a cold engine drip oil out of the breather? If you're bored or
have any answers... read on.

Lycoming IO-540 C4B5

Like some of the other owners in the group, we've had a mystery oil leak
on
one of our engines. Nothing severe, not enough to show up as "missing" on
the dip stick. Primarily just a nuisance.

Last week ours took on a new characteristic that I can't figure out, so
I'll
throw a few details at the group to see what tid bits of knowledge,
experience, and plain ole guessing can be generated.

Original leak seemed to be coming from around an oil return hose on our #3
cylinder. Nearly impossible to get my hands on with the bottom cowl in
place, I tightened it up as much as I could without replacing the hose
clamp. Occasionally notice a drop of oil hanging from the bottom of the
inboard end of the hose.

Oil accumulates along the back side of the fuel injector throttle body in
a
valley where the throttle body moves upward to connect to the air intake
scat tube.

Small amounts of oil are obviously flying around inside the cowl as single
drops can be found on the bottom of collection points such as bolt heads
and
flanges. The floor of the bottom cowl never has any streaks, streams, or
oil lines but is generally covered with a very thin coat of oil that
returns
even after washing and wiping it down.

The above observations were constant all summer when using Aeroshell W100.
Never displacing an amount that was observable as a loss on the dipstick.
Normally both engines use about a quart of oil every 6-8 hours if we fill
them up to 12 quarts. If we leave them down around 10 quarts, they can go
up 10 hours before needing to add a quart.

Ok, new observations and clues.
As winter approached we changed oil and filters and switched from W100 to
15W-50. We've flown about 10 hours on this oil change so far, but this is
what I've noticed.

A puddle of oil, I'd say about 2 tablespoons full, appeared on the floor
directly under the breather tube the day AFTER as short 30 minute flight.
The plane came out of a heated hanger and was completely warm and toasty,
I
flew it home, tucked it away, no drips or drops as I left our old unheated
hanger. The NEXT evening I went up to the hanger and the puddle was
discovered. I wiped it up, opened the cowls, looked around and everything
seemed as described above (a few drops hanging here and there, oil along
the
backside of the throttle body ect.)

The following night, I needed to shovel the snow away from the hanger
door,
so I went in and there it was AGAIN! The plane hadn't moved, hadn't
flown,
engines not started, but it dripped another 2 tablespoons full of oil out
of
the breather tube and onto the floor.

The oil I wiped up off the floor is usually darker colored than the oil on
the dipstick.

So here's what's got me puzzled.... why would a cold engine drip oil out
of
the breather? Especially the day AFTER it was flown? I can understand if
there was pressure remaining in the sump there may be some spit out the
breather, but after 24 hours, I can't believe there would be any pressure
in
the sump.

Second thought, which I've been told Lycoming's don't have a problem with,
would be a leaking intake valve guide. Could that be seeping oil back
down
through the intake and somehow make it to the throttle body? One of the
breather lines goes to the back side of the throttle body and then (I
assume, can't see it) enters the sump. The other breather line goes up
towards the back of the accessory case, towards the oil pump I believe, I
need to investigate this line more, I couldn't see very well.

Any ideas?

Thanks!
Jim