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