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oil sucked out of my 912

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Ralph B

Joined: 14 Apr 2007
Posts: 367
Location: Mound Minnesota

Posted: Fri Dec 04, 2009 8:33 am Post subject: oil sucked out of my 912

Guys,



My 912 is low on oil occasionally and it's not because the engine is burning it. It's being sucked out of the vent tube. This tube runs down alongside the bottom of the engine and exits in front of the prop. I find evidence of oil on the prop if I fill the oil to the marks on the dipstick.



Is there a better way of venting the oil canister?



The tube is flat on the bottom and Mark German (builder) thinks the venturi effect is sucking out the oil. He told me to file the vent tube at about a 45 deg angle so it would have an opening towards the front. Then it will have a positive pressure instead of a negative one.



What kind of oil canister venting do some of you guys have on your 912's?



Ralph B

_________________
Ralph B

Kolb Kolbra 912uls
N20386
550 hours

rlaird

Joined: 10 Jan 2006
Posts: 373
Location: Houston

Posted: Fri Dec 04, 2009 8:44 am Post subject: oil sucked out of my 912

My tube runs all the way down to near the bottom of a leg.  No issues with it.  I'd have to double-check, but I think it curves just a tiny bit, away from the leg, toward the back... the tube is behind the leg, thus out of the airstream. 



On Fri, Dec 4, 2009 at 10:33 AM, Ralph B <ul15(at)juno.com (ul15(at)juno.com)> wrote:

[quote] --> Kolb-List message posted by: "Ralph B" <ul15(at)juno.com (ul15(at)juno.com)>

 

 Guys,

 

 My 912 is low on oil occasionally and it's not because the engine is burning it. It's being sucked out of the vent tube. This tube runs down alongside the bottom of the engine and exits in front of the prop. I find evidence of oil on the prop if I fill the oil to the marks on the dipstick.

  

 Is there a better way of venting the oil canister?

 

 The tube is flat on the bottom and Mark German (builder) thinks the venturi effect is sucking out the oil. He told me to file the vent tube at about a 45 deg angle so it would have an opening towards the front. Then it will have a positive pressure instead of a negative one.

  

 What kind of oil canister venting do some of you guys have on your 912's?

 



 [b]

_________________
~~~~~~~~~~~~~~~~~~~
Robert Laird
formerly: MkIIIc w/ 912ULS & Gyrobee
current: Autogyro Cavalon w/ 914ULS
Houston, TX area
http://www.Texas-Flyer.com

by0ung(at)brigham.net
Guest

Posted: Fri Dec 04, 2009 11:44 am Post subject: oil sucked out of my 912

The tube is flat on the bottom and Mark German (builder) thinks the venturi

effect is sucking out the oil. He told me to file the vent tube at about a

45 deg angle so it would have an opening towards the front. Then it will

have a positive pressure instead of a negative one.



What kind of oil canister venting do some of you guys have on your 912's?



Ralph B

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>


	


I don't think that will make any difference....   the blow by gasses that

force the oil from the crankcase to the oil tank are vented out the tube.

There is always a positive pressure on it.



   If  you ran the hose into a small plastic bottle, then created a vent

tube that was about 1/3 down from the top.  The plastic bottle would trap

the oil. And would have to be emptied every now and then.  With the new vent

not being at the top would keep the oil contained if you went into a

negative g condition.



As for me I just wipe off the prop.

Boyd Young

MKIII

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Sat Dec 05, 2009 5:25 am Post subject: Re: oil sucked out of my 912

My 912 oil vent tube goes into a plastic bottle filled with a brass scrubber pad. the vent tube end is about an inch from the bottom of the bottle. A bit of oil will collect in the bottle which I then suck or dump out. Never any oil on the bottom of the plane. This is simple, cheap and works well

_________________
Ron Lee
Tucson, Arizona

NeilsenRM(at)comcast.net
Guest

Posted: Sat Dec 05, 2009 8:23 am Post subject: oil sucked out of my 912

They make a after market breather kit for VWs (you would find it in a dune 

buggy catalog) for less than $30 that I have one installed on my engine. The 

breather box is a small foam filled vented aluminum box with ports for two 

valve covers and the main VW breather three total. The ports are installed 

low in the box so that any captured oil will drain back into the engine. The 

breather requires no maintenance and keeps oil off my tail feathers.



The engine still leaks a very small amount of oil but it doesn't come from 

the breather like before. Great Planes aircraft and Valley Engineering (my 

redrive manufacturer) both have oil separators that I have tried but didn't 

work.



Rick Neilsen

Redrive VW powered MKIIIC



---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Dec 05, 2009 8:53 am Post subject: oil sucked out of my 912

> They make a after market breather kit for VWs (you would find it in a 

dune

 	  Quote: 	
		   buggy catalog) for less than $30 that I have one installed on my engine.

 Rick Neilsen


	


Rick N/Gang:



I was surprised to learn, after putting a few hours on my first 912 in 1994, 

that a lot of waste from the combustion process is dumped out the oil tank 

vent tube.  This stuff is nearly clear and looks, feels, and smells like a 

solvent.  Also, any condensation in the engine is dumped out the vent tube.



I don't want to restrict this vent to keep my airplane tidy.  Therefore, 

you'll usually find oil/solvent residue on my prop blades, radiator/oil 

cooler.



One way to keep the airplane cleaner is not overfill the oil tank.  Burp the 

crankcase by following the procedure described in the owners manual to 

insure the oil level is correct.  If I overfill, which I routinely do, the 

first negative G situation I get into pushes oil to the top of the oil tank 

where crankcase pressure  promptly pushes it into the vent tube.  That 

really makes a mess.



Normally, it is not a problem if I don't overfill.



john h

mkIII -  Cold and grey at hauck's holler, alabama.

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

NeilsenRM(at)comcast.net
Guest

Posted: Sun Dec 06, 2009 8:58 am Post subject: oil sucked out of my 912

John



Agreed it is best not to restrict the gases that get vented by any breather 

system but if you can separate the gas from the oil mist that does come out 

of my VW it is a good thing. The very low cost breather/oil separator that I 

use works very well and allows enough volume of air movement that oil 

doesn't find a way out in other areas that had plagued my older VW engines. 

Remember there are others putting VWs on Kolbs.



On my direct drive VW I had a long tube that vented this oil mist out the 

bottom of the cage along with a lot of nasty looking stuff that would drip 

out back in the hanger. I found that adding the long tube the same size as 

the breather line tended to restrict the breathing enough that oil would 

find its way out of the engine in other areas. Later I removed the long 

breather tube and found my oil consumption reduced a bit but my tail 

feathers were still well oiled.



I assumed that the high priced Rotax 912 series engines would have solved 

this issue and maybe they have by keeping the oil level lower. I was just 

surprised to hear others comment about this issue with their 912s.



Rick Neilsen

Redrive VW Powered MKIIIC



---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sun Dec 06, 2009 9:26 am Post subject: oil sucked out of my 912

> I assumed that the high priced Rotax 912 series engines would have solved

 	  Quote: 	
		   this issue and maybe they have by keeping the oil level lower. I was just 

 surprised to hear others comment about this issue with their 912s.



 Rick Neilsen


	


Rick N/Gang:



Not really an issue for our "high priced" Rotax 912 engines.



This solvent looking/smelling fluid needs to be flushed out of the system, 

and that is what is happening.  It is not that much, a few drops now and 

then.



The only time I get oil out of the "oil tank" vent line is when I 

accidentally overfill the oil tank during oil changes, and/or experience a 

severe down draft or a hard landing.



We use a dry sump crankcase on our engines.  Oil is returned to the oil tank 

from the crankcase by blowby pressure which is 3 to 5 psi.  This also allows 

the engine to purge itself of contaminents during this process.  I never 

realized how much blow by there was in an internal combustion engine until I 

went through the Rotax Factory 912 School.



A few years ago, Rotax changed the oil tank dip stick operating range.  The 

low and high level marks were raised to increase oil capacity.  I think this 

may aggrevate the problem of negative G's and  oil blown out the vent line.



If folks are concerned about oil getting on their airplanes, I think the 

vent line catch bottle is a good idea.  I don't use one because that is just 

one more thing to pay attention to.



Rotax probably could spend a lot of money to develope a new oil tank with 

new innards to prevent this from happening, but I don't think it would be 

worth the money.



I'm not whining about the problem because it only happens when I goof up and 

overfill or get in some pretty violent weather.



An added tidbit:  My old Dodge/Cummins engine is a 1992 model.  I uses the 

old fashioned method of venting crankcase to the atmosphere.  During 

operation on the highway it is venting gases and solvents to the atmosphere, 

just like the 912.  After a long hard pull, the Cummins will drip oil and 

solvents from the crankcase vent tube.



Guess Rotax could go to a closed crankcase system, but then the little 

engine would have to eat all that crud in order to get rid of it.



john h

mkIII



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Bickham

Joined: 10 Jan 2006
Posts: 170
Location: St. Francisville, LA

Posted: Mon Dec 07, 2009 5:21 am Post subject: Re: oil sucked out of my 912

Just wanted to add this one for consideration....



John H pointed this out to me on our trip out west in May.  Play with the location and direction of your vent hose.  Originally, the last foot of mine was horizontal and terminated within about 6" of the prop.  We went through some rough stuff on the trip to MV on then to SE Oregon.  I had some pretty good oil/dust residue on my tail section.  



With John H's recommendation, I turned the last 6" down and further away from my prop.  Since then things have been better.  Haven't flown in that much bumpy air since then.  But prop and far aft of engine staying a bit cleaner than is same conditions prior.



Easy and cheap experiment if you wanted to check.

_________________
Thanks too much,

John Bickham
Mark III-C w/ 912UL
St. Francisville, LA

I know many pilots and a few true aviators. There is a distinct difference that I have the greatest respect for.

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Dec 07, 2009 6:46 am Post subject: Re: oil sucked out of my 912

My Jabiru has a rather small home-made air/oil separator with a drain cock at the bottom with a hose that extends below the bottom of the fabric in the back. I empty that after every flight or two, usually just a few drops but what comes out of there I would not want to route back to my engine, thought some Jabiru operators do. That stuff is nasty. The air/oil separator also has a hose connected to the air outlet that goes overboard too to make sure there is no back pressure and the crankcase can still breath normally if the separator fills up.



Once I started emptying the separator regularly and keep the oil level at the currently recommended relatively low level (Jabiru changed their recomendation too) I get zero oil streak on the Slingshot tail.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Vic Peters

Joined: 30 Oct 2009
Posts: 54
Location: Millinocket, Maine

Posted: Mon Dec 07, 2009 7:12 am Post subject: oil sucked out of my 912

All or none,



I simply put a loop up from the oil tank. Oil drains back water vapor and 

whatever else

blows out directly at prop no mess.



I've seen drawings of other craft that cut a slot in the overflow tubing 

inside the cowling

and extend the tube outside. Any excess vacuum only pulls cowling air.



Vic

Xtra 912

_________________
Vic
912ul Xtra
Maine
Too old to cut the mustard but not the cheese.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Dec 07, 2009 7:29 am Post subject: oil sucked out of my 912

 	  Quote: 	
		   I simply put a loop up from the oil tank. Oil drains back water vapor and 

 whatever else

 blows out directly at prop no mess.



 I've seen drawings of other craft that cut a slot in the overflow tubing 

 inside the cowling

 and extend the tube outside. Any excess vacuum only pulls cowling air.



 Vic


	




Vic/Gang:



There is a steady stream of 3 to 5 psi air (blowby) exiting the vent tube. 

I would think, in a down draft, serious negative G situation, when the oil 

hits the lid of the oil tank, it will be going out the vent, loop or not.



Personally, I want the waste material that is a byproduct of gasoline engine 

to be dumped overboard.



This is the way I operate my 912ULS.  May not be recommended or approved by 

Rotax.



The 912ULS uses crankcase pressure to push oil out of the crankcase back to 

the oil tank.  As long as the engine is running, there is 3 to 5 psi 

pressure in the vent line.



john h

mkIII - When it gets warm enough to fly, it will be raining.  ;-(

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

ulflyer(at)verizon.net
Guest

Posted: Mon Dec 07, 2009 7:44 am Post subject: oil sucked out of my 912

Hi Ralph,

Man you testing this old guys memory.  Look at the crank case vent 

tube on some small certified aircraft like a 150 or 152 Cessna.  Its 

a little fuzzy but on our 115 HP Lycoming powered 1973 Citabria I 

believe the end of crank case vent tube was cut at an slight 

angle.  Can't recall if the angle faced forward or rearward.  It also 

had a hole of about 3/16" drilled in either the front or rear side of 

the tube about an inch or so above the end.  According to our A&I 

this hole was there for a purpose if the normal exit should become 

plugged.  I would also think the hole may reduce any siphon effect.

jerb



At 08:33 AM 12/4/2009, you wrote:

 	  Quote: 	
		  



Guys,



My 912 is low on oil occasionally and it's not because the engine is 

burning it. It's being sucked out of the vent tube. This tube runs 

down alongside the bottom of the engine and exits in front of the 

prop. I find evidence of oil on the prop if I fill the oil to the 

marks on the dipstick.



Is there a better way of venting the oil canister?



The tube is flat on the bottom and Mark German (builder) thinks the 

venturi effect is sucking out the oil. He told me to file the vent 

tube at about a 45 deg angle so it would have an opening towards the 

front. Then it will have a positive pressure instead of a negative one.



What kind of oil canister venting do some of you guys have on your 912's?



Ralph B



--------

Ralph B

Original Firestar 447

N91493 E-AB

970 hours

23 years flying it

Kolbra 912UL

N20386

1 year flying it

110 hrs





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 76174#276174

rlaird

Joined: 10 Jan 2006
Posts: 373
Location: Houston

Posted: Mon Dec 07, 2009 7:48 am Post subject: oil sucked out of my 912

(How can I NOT jump in... this is getting almost as good as SeaFoam! 



The angle cut and backup holes are nice touches... however....  if you get a kink in the tube somewhere between any backup holes and the vent at the top of the tank, then the 912ULS will have trouble circulating the oil through the engine.  Ask me how I know!  :-p

 



  -- Robert

On Mon, Dec 7, 2009 at 9:42 AM, jerb <ulflyer(at)verizon.net (ulflyer(at)verizon.net)> wrote:

[quote] --> Kolb-List message posted by: jerb <ulflyer(at)verizon.net (ulflyer(at)verizon.net)>

 

 Hi Ralph,

 Man you testing this old guys memory.  Look at the crank case vent tube on some small certified aircraft like a 150 or 152 Cessna.  Its a little fuzzy but on our 115 HP Lycoming powered 1973 Citabria I believe the end of crank case vent tube was cut at an slight angle.  Can't recall if the angle faced forward or rearward.  It also had a hole of about 3/16" drilled in either the front or rear side of the tube about an inch or so above the end.  According to our A&I this hole was there for a purpose if the normal exit should become plugged.  I would also think the hole may reduce any siphon effect.

  jerb

 

 

 

 At 08:33 AM 12/4/2009, you wrote:

 

 	  Quote: 	
		   --> Kolb-List message posted by: "Ralph B" <ul15(at)juno.com (ul15(at)juno.com)>

 

 Guys,

 

 My 912 is low on oil occasionally and it's not because the engine is burning it. It's being sucked out of the vent tube. This tube runs down alongside the bottom of the engine and exits in front of the prop. I find evidence of oil on the prop if I fill the oil to the marks on the dipstick.

  

 Is there a better way of venting the oil canister?

 



 The tube is flat on the bottom and Mark German (builder) thinks the venturi effect is sucking out the oil. He told me to file the vent tube at about a 45 deg angle so it would have an opening towards the front. Then it will have a positive pressure instead of a negative one.

  

 What kind of oil canister venting do some of you guys have on your 912's?

 

 Ralph B

 



 --------

 Ralph B

 Original Firestar 447

 N91493 E-AB

 970 hours

 23 years flying it

 Kolbra 912UL

 N20386

 1 year flying it

 110 hrs

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=276174#276174

 

 

 

 

 

 

 

 

	
 

 

 

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[b]

_________________
~~~~~~~~~~~~~~~~~~~
Robert Laird
formerly: MkIIIc w/ 912ULS & Gyrobee
current: Autogyro Cavalon w/ 914ULS
Houston, TX area
http://www.Texas-Flyer.com

elleryweld(at)aol.com
Guest

Posted: Mon Dec 07, 2009 4:10 pm Post subject: oil sucked out of my 912

Thom Riddle

   have you got a print of how that is made ? I know a friend that needs one 

    

   Ellery in Maine 

   Making skis for the Mk3C

 

 

 

   --

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Dec 07, 2009 5:58 pm Post subject: Re: oil sucked out of my 912

Ellery,



I didn't build the airplane but it is a simple device. The breather hose goes into the top. A fitting in the bottom has a shut-off valve with a hose to the bottom of the airplane so you can drain it at your convenience. Near the top but coming out the side is another fitting with a hose attached going overboard also. This last one allows the breather to work and the container just catches the oil and condensation at the bottom. Actually both in inlet and outlet (not the drain) fittings can be in the top or near the top if that is easier to configure.



The container can be made of anything that will stand high oil temperature. To work effectively the container should be more tall than squat but of any volume from a 4-6 oz or so as a minimum. The smaller it is the more often you'll have to drain it. Go to any of the aircraft suppliers and look at their air/oll separators. Mine has the bottom fitting with shut-off valve that most do not. The valve allowing me to decide when to dump it into a waste container instead of dripping all over the airplane. 



I hope this description helps.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

elleryweld(at)AOL.COM
Guest

Posted: Tue Dec 08, 2009 5:36 pm Post subject: oil sucked out of my 912

Thom R

    

   Thanks I will weld up a couple of these  in aluminum They will make a couple of my aviation buddies a great Christmas gift 

    

   Ellery

 

 

 

   --

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