Oil breather drip after shutdown

DesertNomad

DesertNomad

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DesertNomad
Why does a bit of oil drip out the breather tube in the minutes after shutdown and how much is normal? On my Dakota it ends up on the right side of my nose wheel pant and is maybe 1/4 teaspoon or less. Just a few streaks down the side of the pant.

Temperature doesn’t seem to matter but it does seem to happen sooner after shutdown than before the last annual. Before, it probably took 15 minutes or so before dripping but now it is within a few minutes of shutdown.

At annual, they did replace my oil cooler and gascolator which I think also slightly affected where the breather tube comes out since it used to mess up the left side of the nose wheel pant and now is an inch or so to the right so it slides from near the center of the pant then off the right side.

The oil quantity at the dip stick is normal. I have always kept a large cookie sheet under the trailing edge of the nose pant to catch oil and it has always dripped a bit after flights. It just seemed to be a bit more than usual on the last flight.
 
I fly old airplanes...Cessna 195 and F35 Bonanza. A drip from the breather hose is normal for my planes. If oil consumption is normal and compression is normal...I would not worry. Here in the Southeast we also make sure the breather tube is not restricted by mud daubers and such.
 
I concur with Doug. I’ve flown PA28, C150, C172, C182 and they all leaked a bit from the breather tube, often a milk-like, froth. I always monitor oil usage, happy if it’s a quart every 10-12 hours.
 
My bird will not tolerate more than six quarts of oil. My AI and I have talked about it. It is the way it is. After the last annual they forgot and put in 8 quarts. After about 2 hours it was down to six quarts and stayed there after that. What a mess to clean up the bottom of my bird! I wish I had your situation. As long as the oil level is stable a little oil at the breather tube is normal.
 
DesertNomad said:
It just seemed to be a bit more than usual on the last flight.
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FYI: in general, breather systems can be sensitive to tube routing/positioning and in some cases the length/angle of the tube extension into the slipstream. If the breather tube has been moved from its previous position, as you stated, then it's quite possible the breather system "performance" has also changed a bit. Good on you for noticing the difference.
 
DesertNomad, I think you have seen the advice to run your Dakota somewhat lower than the 12 quarts recommended by the POH. You said your oil level is stable, so I suspect what you are seeing is not blowout, but it was worth mentioning.

My Warrior will occasionally drip from the oil breather tube, and I believe DFH65 is probably right--it's oily water condensation.
 
Domenick said:
DesertNomad, I think you have seen the advice to run your Dakota somewhat lower than the 12 quarts recommended by the POH. You said your oil level is stable, so I suspect what you are seeing is not blowout, but it was worth mentioning.

My Warrior will occasionally drip from the oil breather tube, and I believe DFH65 is probably right--it's oily water condensation.
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It's not blowout. I have just under 9 quarts in it. It blows out anything over 10 and I add a quart when it gets to about 8.5. This is just dripping after a flight. I think you are right that it is oil and water.

When I return to my field, I go to get fuel and then back to the hangar. It used to not really drip while I was getting fuel but on the last flight it did. It could just be the temperature and humidity allowing for more drips. It has always dripped in the hangar after a flight but I haven't hung out long enough to see how long it spends dripping. I always return to the hangar the day after flying to put in the cowl plugs (too hot right after flying) and have to clean the nose pant at that point.
 
It’s normal, the Archer does the same thing every now and then.

A few things:
Flying on days with higher humidity or frost, will usually result in having more breather drip, at least in my experience. These conditions provide the right environment for condensation to occur and that results in a higher oil/water mix dripping from the breather tube. Also, what oil are you using? I’ve noticed that the Aeroshell Multigrade tends to create more breather drip than the Phillips does. Typically the lighter the oil, the more likely it is to vaporize.

When the Archer drools it’s usually a chocolate milk colored drip about the size of a half dollar. I would not worry.
 
I use AeroShell 15W50. A half dollar seems about right, but mine lands on the top-rear of my wheel pant and then runs off to the side (formerly the left, now the right). I imagine my breather tube moved slightly after last annual where they needed a new gascolator and things moved a bit. It wouldn't have to move much to change the side that it slides off toward.

I would say mine is more oil color than chocolate milk. I guess I was just surprised to see some on the pant right after shutting down, securing things and stepping out as it usually takes longer than that to start dripping.
 
DesertNomad said:
Why does a bit of oil drip out the breather tube in the minutes after shutdown and how much is normal? On my Dakota it ends up on the right side of my nose wheel pant and is maybe 1/4 teaspoon or less. Just a few streaks down the side of the pant.
Click to expand...

Would parking your plane with the nosewheel hard left or right cause your drip to miss? Just sayin...
 
Easy experiment? Switch oil to straight 100 or Phillips X/C. The drips will likely be reduced significantly. It worked for me.
 
Lycoming breather outlets are directly above accessory case gears. Oil gets flung off the gears. Make a loop up from the breather as high as possible. That’ll help. Keep the breather tube end above the slipstream at the bottom cowl. My Continental breather outlet is in the front. The breather slopes upward until it turns down at the back of the engine. That one loses very little oil but does drip water and oil-water emulsion. Changing oil brands made the biggest impact to slow it down. I use an oil separator on my Lycoming.
 
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Bell206 said:
FYI: in general, breather systems can be sensitive to tube routing/positioning and in some cases the length/angle of the tube extension into the slipstream. If the breather tube has been moved from its previous position, as you stated, then it's quite possible the breather system "performance" has also changed a bit. Good on you for noticing the difference.
Click to expand...
There are several versions of drip catchers on the market.
A simple can works too.
throw a pie pan under proper spot.
 
My plane has a "puke bottle", actually a can that screws into a fitting on the firewall that the breather goes into. Every so often I unscrew it and dump out maybe a tablespoon or two of a milky mix of water and oil, keeps the bottom of the fuselage a lot cleaner. It's easy to make... oh, that's right, you can't do that on certified planes... :p
 
The moisture condenses in the breather tube and mixes with oil film there. Insulating the tube prevents the condensation and the water vapor goes overboard. Less mess.
 
I put a homemade oil separator on a the crankcase vent of a car. Worked great until it froze up and blew the seal off the end of the camshaft.
 
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