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Oil Breather Spews Oil

K

ksouthar

Well Known Member
Ok, may not spews but definitely lubricates the belly!

Looking for recommendations -

The situation:

RV9A with Lycoming 0-320 E3D (150 hp)
Catto 3 Blade FP prop (not that it matters)
Air/Oil Separator (the one Van's sells) installed

The Problem:

After every flight, I get to crawl under the airplane and wipe off the oil that is spewed out of the oil breather line. Not a lot of oil (not enough to drip) but enough to bug the %x#* out of me and after 3 or four hours of flight it goes all the way to the tail.

I have allowed the engine oil level to decline to 6 quarts. I have positioned and re-positioned the breather tube everywhere from about an inch above the exhaust pipe to as much as 3 inches above the exhaust. And still I have oil.........

Multiple detailed cowling-off inspections have failed to reveal any other source of the oil. The end of the breather tube always has a ring of oil beaded up on the edge and visible oil up into the tube. The exhaust stack is discolored from the effect of burning off the oil that lands on it.

Suggestions and recommendations or your experience? Van's support reply was "I run mine down to 6 quarts and it is pretty good there".

Keith
N355RV
20 hours flying
 
Two thoughts:

* My breather is about 1/4" from the exhaust stack
* You only have 20 hours on the engine? If so, I'd say wait until you get to 50 to really worry about this. I had more oil on my plane's belly at first. Now things are mighty clean.
 
I assume that you are using a straight mineral oil such as Shell 100 (50-W) for the break-in period of 55 hours. A change at 5 hours, 30 hours and at 55 hours. I would also hope that you are checking the oil & filter for metal. A bit would be normal at this point. A lot would be cause for concern. I have been told by a reliable source that using the multi grade synthetic blended oil such as Shell 15-50 will not allow your rings to properly seat.

I would also guess that if everything is opperating properly you are using about one quart of oil to every 3 to 7 hours at this point. By the 55 hours that consumption should deminish to about one quart every 10 to 25 hours. Unfortunatly most of that ends up on your belly.

I don't know if it is called for in the plans but the person that built my airplane and other 4's I've seen have the breather tube routed through the fuslage to the tail which pretty much only oils the tail wheel. If your oil consumption is normal then you might consider such a re-rout of the breather tube.

I am just quoting what I have recently heard and I am no expert. Maybe someone with much more expertise than I have can chime in here and get you headed in the right direction or set your mind to ease. :confused:
 
Use 6 quarts max

ksouthar said:
I have allowed the engine oil level to decline to 6 quarts.
Click to expand...

The other two quarts are what's on your belly. They all do that. The correct oil level for a Lyc 0320/0360 is 6 quarts on the dipstick (which is actually about 7 counting the filter). Any more than that and it will just spit it out.

The reason your engine has an eight quart capacity is certification rules that originated back when engines were round and oil consumption was measured in gallons.
 
I fly a C-172 with the 0-320. Anything more than 6 qts gets spit right out. I only add a quart when its under 5 on the dip stick, that way I always keep it under 6. I've been doing this for 10 years and it seems to work well.

Bill
 
jonbakerok said:
The other two quarts are what's on your belly. They all do that. The correct oil level for a Lyc 0320/0360 is 6 quarts on the dipstick (which is actually about 7 counting the filter). Any more than that and it will just spit it out.
QUOTE]


Konbakerok is right. 6 quarts on the stick. What you're seeing sounds normal to me. Oil on the belly is normal.
Click to expand...
 
The only Lycosaur that doesn't drip oil is one that never runs!

If the belly of my RV8 isn't coated with oily grime, then either there is something seriously wrong with the engine, or I'm not flying enough. My mentors through the build of my airplane gave me a care kit after first flight...dubbed the "Cessnabelly care kit". :D consisting of rags, wax, simple green....squeegee...

The only only other likely source of really problematic oil discharge out of the breather is crankcase pressurization from piston ring blowby. Highly unlikely in a new engine, but may actually happen more so until the rings are seated and the mineral oil is gone. Once everything is "burned in" and happy, it should get better. And, definitely keep the level no higher than 6 qt. on the stick.
 
Grease Monkey

ksouthar said:
I have allowed the engine oil level to decline to 6 quarts. I have positioned and re-positioned the breather tube everywhere from about an inch above the exhaust pipe to as much as 3 inches above the exhaust. And still I have oil......... Keith N355RV 20 hours flying
Click to expand...
6 qt should be a MAX, allow it to vary from 5 to 6 qts. (Sometimes for cross country, emptying the last bit of oil from a bottle I might go 6.2 qts, but 6 qts is a typical MAX.)

The breather has an angle cut on it? It is easy to create a vacuum across the breather tube end. The acute angle cut on the end should be into the direction of air passing the tube end.

What is the engines compression and oil use? If the compression is low or oil use high you could have too much blow-by. It does not take a lot of oil to make a mess, but if the engine has a bad ring you can pump a lot of stuff out the breather.

Here is a maintenance trick where you connect an airspeed indicator to the crankcase! You make a special cap where the dip stick goes, with a hose fitting. A hose runs to the cockpit, connected to an airspeed indicator. Do a ground run up. Reading the airspeed indicator the max airspeed is about 45-55 mph, which is an equivalent pressure of 1.23 in-h2o. Here is an excellent article: http://www.sacskyranch.com/eng30.htm )

My philosophy is an air-oil separator is not needed or necessary on a healthy Lyc following the 6 qt rule (Despite the hype the M-40 guy says who sells his oil separator, which has more bull than cattle ranch, 6 qts is fine.)

Assume you are not doing acro.
 
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belly oil

Our Pitts S-2A has a tube from breather to dump point by tailwheel. Works great in summer but close it off in winter to avoid condensation freezing and causing blow-out of front seal. Then we use a short tube to dump oil in the exhaust dishcarge area. Van I believe recommends a small hole drilled in the breather at the bottom of the engine sompartment to allow relief if the tube is blocked farther down. Encountering frequent neg G causes more oil than upright flight but we still get only moderate amount on the belly during the winter. Wait until spring to clean it up since it's cold here! Sorry to hear your air=oil separator doesn't make it cleaner. Our IO-360 also does well with oil at 6 qts on dipstick - higher blows out fairly quickly. Haven't noticed higher op temps at this level despite some allegations by separator maker that more oil cools much better. Seems to me if oil cooler is adequate the oil temp should be OK. Anybody have thoughts on this? Bill
 
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