have no professional or expert qualifications of any kind.
It's fully up to you to check any information you
find here with
standard aviation industry sources such as
manuals, flying instruction books and, above all,
||Click on the picture for high-resolution
I've have seen people use the hose that goes up and over the cylinders, then
down, behind the engine, to the bottom of cowl. This causes the first part of
the hose to be uphill. That may help some.
I've seen people install an oil/air separator and that can help some.
If one of those is enough, that's nice.
I've seen oil come out of a Coupe O-200 engine installation so fast that
caused a forced/precautionary landing in a field (successful) because of loss of
oil pressure. It may be that the O-200 splashes oil more vigerously inside the
This last instance was ONLY solved by adding the breather-elbow extension.
The extension is a tube that gets soldered (silver-solder?) to the crankcase
side of the breather-elbow and acts as a pipe sticking a certain fraction of an
inch inside the crank-case.
The breather-elbow extension works, it seems, because oil is splashed around
the inside of the crankcase. Since there's always air-flow out the breather,
it'll suck oil from the case walls right along with the air. The extension makes
the inlet suck air that's not right along the crankcase wall. The oil on the
walls seems not to go along. This seems to put a firm and immediate stop to the
I think I heard this elbow extension was a standard part on a later Coupe
engine (?C-90?) for a while. It can be fabricated by someone with proper skill.
I would make very xxxxx sure the mechanic attaching the extension knows what
he's doing since I wouldn't want even a short aluminum tube bouncing around
inside my engine. I have seen one instance (cited above) where this was the only
thing that made much difference to the problem and this solved it completely. I
heard of some other instances where this solve the person's problem.
Again, I ain't a mechanic and my memories of this are 8-10 years old. Is
there someone out there who can give exact and specific info on how to
buy/fabricate a breather-elbow extension?
Here's info from John at Skyport
P.O. Box 249, Rensselaerville, NY 12147
Dip stick mystery.
The tube the dip stick is in is generally below the level of the oil in the
tank. The dip stick cap seals the top of the tube. So, when you shut down the
engine, you have a sealed tube containing warm air in the top, the bottom of
which is submerged in oil. As the trapped air cools it contracts (a lot more
than the hot oil would) and draws oil up into the tube. When you open the cap
the oil drops back down into the tank, seaking its own level, but the reading on
the stick is artificially high. The second reading is the correct one.
Oil Fill level and blow out from the breather tube
4-5 quarts is enough unless you experience engine cooling problems, which
you shouldn't. The 6 qt requirement is arrived at by virtue of a certification
requirement: The engine must be able to run without exceeding its maximum
allowed oil temperature with half of the specified oil level, thus 3 quarts is
enough and 6 is what they mark the capacity at. This is why there is a slight
difference between the C75, C85 and C90 oil "capacities". Same tank, just
All C-series Continentals, including the O200 have a dry sump, so,
theoretically, any oil level that is contained entirely within the tank should
be OK. Lycomings blow oil when the level is too high by virtue of the fact that
the crankshaft beats the oil around. This should not happen on the C-series.
Regardless, there is anecdotal evidence that higher oil levels result in more
oil out the blowby tube. Go figure.
There are a number of oft overlooked causes for oil out the blowby tube.
Here are some in no particular order:
- Leaking crankshaft seal allowing ram air to pressurize the crankcase.
- Excessive blowby pressurizing the crank case.
- Blowby tube incorrectly positioned, resulting in a low pressure in the tube
- Missing extension on the crankcase vent elbow, especially on engines with
accessories on the nose (vacuum pump, fuel pump, injection pump).
An oil separator should not be necessary, unless you're trying to keep a show
quality plane spotless. If you've got excessive oil on the belly after a couple
of hours, something is wrong. Putting a home brew oil trap on the blowby
tube can be problematic, regardless of the legalities. If, for example, it
freezes up, you can blow a seal and loose a lot of oil in short order. Better to
get it working correctly, and if you're still dissatisfied, add an approved
Better to correct the problem than put expensive lipstick on a bulldog. And
end up with bulldog teeth marks on your butt