Thanks. I may do a little testing at the 6 to 7 quart level
and see how the consumption looks after an hour.

Ronnie

wrote in message
. ..
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