oil blow out IO-360

I have an IO-360-A3B6 900 SFNEW in '97. I used to be able to keep about
7 quarts in it without it blowing out. Now it seems to be blowing oil
down to about 5.5 quarts. Since I live in the 100F OATs part of the
country, the extra oil really helps cooling.
Should I worry about what is causing the extra oil blow out or just
chock it up to an aging engine. I know some engines always blow out to
6ish quarts.
If I shouldn't worry about the extra blow out I'll just put a separator
on it, but I don't want to mask a problem first. One recent change is
we raised the oil pressure since the regulator had been slipping prior
to annual.

-Robert

Do a differential compression test and pay attention to
valve guides play and seals, often the oil is not being
blown out the breather, but is leaking around the valves
[even one valve] and burning. If you have high leakage
during the differential compression test, you're getting too
much blow-by and that is raising the crankcase pressure and
blowing oil out the breather tube. If the breather is
blocked, it will blow the main seal and you'll see oil
behind the prop. If the oil level goes down fast and then
stabilizes, you may have a dipstick that is not calibrated
properly and you're over filling.

The engine is old, nearly ten years, check all the seals and
mating surfaces. You only have 900 hours, but that is less
than 100 hours a year. Corrosion in the cylinders and blow
by, and oil being sucked past the ring into the combustion
chamber are all possible, Check valve guides and seals,
differential compression and if available, borescope it.
Higher oil pressure would increase the leakage, but not
effect the valve guides or rings. An oil separator will
only help if the oil is going out the breather tube.


--
James H. Macklin
ATP,CFI,A&P



"Robert M. Gary" wrote in message
ups.com...
|I have an IO-360-A3B6 900 SFNEW in '97. I used to be able
to keep about
| 7 quarts in it without it blowing out. Now it seems to be
blowing oil
| down to about 5.5 quarts. Since I live in the 100F OATs
part of the
| country, the extra oil really helps cooling.
| Should I worry about what is causing the extra oil blow
out or just
| chock it up to an aging engine. I know some engines always
blow out to
| 6ish quarts.
| If I shouldn't worry about the extra blow out I'll just
put a separator
| on it, but I don't want to mask a problem first. One
recent change is
| we raised the oil pressure since the regulator had been
slipping prior
| to annual.
|
| -Robert
|

Jim Macklin wrote:
The engine is old, nearly ten years, check all the seals and
mating surfaces. You only have 900 hours, but that is less
than 100 hours a year. Corrosion in the cylinders and blow
by, and oil being sucked past the ring into the combustion
chamber are all possible, Check valve guides and seals,
differential compression and if available, borescope it.
Higher oil pressure would increase the leakage, but not
effect the valve guides or rings. An oil separator will
only help if the oil is going out the breather tube.

The only place I'm seeing any oil is at the breather. I had a full
prop/gov overhaul last year and they replaced the front engine seal. I
wasn't having any problems with the prop, I had it overhauled because
oil was leaking from the gov. Now I think I've got a clean enough
engine that I can actually tell where the oil is leaknig from.

-Robert

You might see about plumbing in a pressure gauge to read the
crankcase pressure in flight, also, there should be a baffle
to keep the oil from directly splashing on the breather
pick-up.

It is possible that the work that was done reduced the
leaking from the crankcase [reduced venting] and it is now
increased at the breather. If there is too much blow by, a
top overhaul or perhaps just a bad cylinder needs honed and
new rings. But a sudden change in the oil usage pattern is
cause for more investigation. You see oil at the breather
because it is not burned, but is atomized particles and
vapor. But you can be burning oil because of bad rings or
valve guide leakage and that could be masked in the exhaust
stack. Check plug condition and the stacks should be chalky
gray, not black or brown greasy. Have someone do a full
power run-up and you look at the exhaust for color, oil
smoke
is bluish, excess fuel is black smoke. White smoke is a
cold engine and water condensation, or a water jacket leak
on a water cooled engine.

see
http://www.lycoming.textron.com/main...ons/index.html

--
James H. Macklin
ATP,CFI,A&P

"Robert M. Gary" wrote in message
ups.com...
|
| Jim Macklin wrote:
| The engine is old, nearly ten years, check all the seals
and
| mating surfaces. You only have 900 hours, but that is
less
| than 100 hours a year. Corrosion in the cylinders and
blow
| by, and oil being sucked past the ring into the
combustion
| chamber are all possible, Check valve guides and seals,
| differential compression and if available, borescope it.
| Higher oil pressure would increase the leakage, but not
| effect the valve guides or rings. An oil separator will
| only help if the oil is going out the breather tube.
|
| The only place I'm seeing any oil is at the breather. I
had a full
| prop/gov overhaul last year and they replaced the front
engine seal. I
| wasn't having any problems with the prop, I had it
overhauled because
| oil was leaking from the gov. Now I think I've got a clean
enough
| engine that I can actually tell where the oil is leaking
from.
|
| -Robert
|

It seems like I'm agreeing with Jim these days, I'd also say that something
is creating excessive case pressure. Along those lines I just tore down a
horizontally opposed Kohler that was blowing oil from the breather faster
than I could dump it in. It had blown a cylinder barrel seal, not a gasket,
just an RTV seal. The key is that something caused the seal to blow. What
did I find? Cracked exhaust valve guide that allowed exhaust pressures into
the case.

I think a valve wobble test and compression test could shine a lot of light
on your problem.

Jim


"Robert M. Gary" wrote in message
ups.com...
I have an IO-360-A3B6 900 SFNEW in '97. I used to be able to keep about
7 quarts in it without it blowing out. Now it seems to be blowing oil
down to about 5.5 quarts. Since I live in the 100F OATs part of the
country, the extra oil really helps cooling.
Should I worry about what is causing the extra oil blow out or just
chock it up to an aging engine. I know some engines always blow out to
6ish quarts.
If I shouldn't worry about the extra blow out I'll just put a separator
on it, but I don't want to mask a problem first. One recent change is
we raised the oil pressure since the regulator had been slipping prior
to annual.

-Robert

Jim Burns wrote:
It seems like I'm agreeing with Jim these days, I'd also say that something
is creating excessive case pressure. Along those lines I just tore down a
horizontally opposed Kohler that was blowing oil from the breather faster
than I could dump it in. It had blown a cylinder barrel seal, not a gasket,
just an RTV seal. The key is that something caused the seal to blow. What
did I find? Cracked exhaust valve guide that allowed exhaust pressures into
the case.

Would that show up in a compression test though? I"m getting 79's all
around in the compression test. The IA seemed impressed with the
compression. Also, my EGTs seem to be running about the same.

-Robert

No, remember on a compression check your valves are closed, thus why I
suggested the valve wobble test. Not saying the guide is cracked, but it or
they could be worn. I was just trying to keep the symptom (excess oil out
the breather) separated from the cause (unknown) and relate what I had
discovered.

Let us know what you find.
Jim

"Robert M. Gary" wrote in message
oups.com...

Jim Burns wrote:
It seems like I'm agreeing with Jim these days, I'd also say that
something
is creating excessive case pressure. Along those lines I just tore down
a
horizontally opposed Kohler that was blowing oil from the breather
faster
than I could dump it in. It had blown a cylinder barrel seal, not a
gasket,
just an RTV seal. The key is that something caused the seal to blow.
What
did I find? Cracked exhaust valve guide that allowed exhaust pressures
into
the case.

Would that show up in a compression test though? I"m getting 79's all
around in the compression test. The IA seemed impressed with the
compression. Also, my EGTs seem to be running about the same.

-Robert

Jim Burns wrote:
No, remember on a compression check your valves are closed, thus why I
suggested the valve wobble test. Not saying the guide is cracked, but it or
they could be worn. I was just trying to keep the symptom (excess oil out
the breather) separated from the cause (unknown) and relate what I had
discovered.

If it were caused by a valve problem though would the oil still come
out the breather? My engine seems extreamly clean of oil. I can see oil
dripping from the breather.

-Robert

Check the valve guides and seals, with the valve closed,
compression will be good. But when the valve opens, if the
guide is worn or the seal is bad, oil will be sucked from
the top end.


"Robert M. Gary" wrote in message
oups.com...
|
| Jim Burns wrote:
| It seems like I'm agreeing with Jim these days, I'd also
say that something
| is creating excessive case pressure. Along those lines
I just tore down a
| horizontally opposed Kohler that was blowing oil from
the breather faster
| than I could dump it in. It had blown a cylinder barrel
seal, not a gasket,
| just an RTV seal. The key is that something caused the
seal to blow. What
| did I find? Cracked exhaust valve guide that allowed
exhaust pressures into
| the case.
|
| Would that show up in a compression test though? I"m
getting 79's all
| around in the compression test. The IA seemed impressed
with the
| compression. Also, my EGTs seem to be running about the
same.
|
| -Robert
|

The breather exhausts excess pressure built up in your crank case. Anything
that would allow pressure created in the combustion chambers into your crank
case can lead to additional pressure and excess oil being emitted from your
breather along with the gasses. A bad oil ring on a piston or anything not
sealing in the valve train... valve not seating properly or a worn valve
guide.

I'm not an A&P, and this would be better confirmed by Jim or others, but I
would imagine that either a oil return line or even a pushrod sleeve would
allow pressure from a cylinder head into the case. Guys?

Jim

"Robert M. Gary" wrote in message
ups.com...

Jim Burns wrote:
No, remember on a compression check your valves are closed, thus why I
suggested the valve wobble test. Not saying the guide is cracked, but
it or
they could be worn. I was just trying to keep the symptom (excess oil
out
the breather) separated from the cause (unknown) and relate what I had
discovered.

If it were caused by a valve problem though would the oil still come
out the breather? My engine seems extreamly clean of oil. I can see oil
dripping from the breather.

-Robert