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Geoff Heap
Joined: 12 Jan 2006
Posts: 266
Location: Lindenwold, New Jersey
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 Posted: Mon Nov 22, 2010 6:19 am Post subject: I can't burp the oil tank on my 912 UL. Could use some help |
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Hey guys.
I'm not flying yet, in fact I have not started the engine yet (912 UL). I've been neglecting it and concentrating on the building. Now I find that I cannot 'burp' the oil tank . The oil level in the tank has been real low but I know that it was high at one time because I'm the one that filled it. I know it just ran down into the crankcase. So I hand propped it again no end of times. No 'burp' and the oil level would not come up. So I broke the connection under the engine and ran all the oil down into a clean plastic coffee can. I got slightly over half a can, about a quart. I re connected the crankcase plug and poured the retrieved oil into the tank. Dip the tank and it’s at FULL level. I let it sit for 2 days and then Hand propped it over 10 full revolutions. Still nothing. During the 2 days, some of the oil should have leaked into the crankcase. Have I got an airlock somewhere that’s preventing the oil from pumping back to the tank? I'd appreciate some advice……Geoff
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Dual controls. Dynon 180. Icom 210 Garmin 296. Becker transponder. Sigtronics intercom. Electric flaperons. |
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dashwood
Joined: 24 Jan 2009
Posts: 73
Location: sw ontario canada
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| Posted: Mon Nov 22, 2010 10:55 am Post subject: Re: I can't burp the oil tank on my 912 UL. Could use some h |
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if you are sure of your hose connections to the tank. just keep flipping the prop. if you just keep spinning it over aimlessly it will take 20 or more.... i usually turn trough 1 or 2 fins then bring up to compression on the next and hold there for 3 or 4 seconds then next fin to compression hold there for 3 to 5 sec. repeat this and you can burp sooner with less rotations. give time for the air to bleed by the rings on a new tight engine. usually only takes 2 or 3 more fins like this.
your last post got me to think-in some more about this. i am also checking valve seal while doing this maneuver. you will get to know what a good compression bump feels like and a bad leakby should be easier to notice.keep an ear to the exhaust sounds as well.
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Ross Alexander: CH701 driver 912ul 788tt
It only takes two things to fly, airspeed and money
Last edited by dashwood on Mon Nov 22, 2010 1:56 pm; edited 2 times in total |
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Geoff Heap
Joined: 12 Jan 2006
Posts: 266
Location: Lindenwold, New Jersey
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| Posted: Mon Nov 22, 2010 11:43 am Post subject: Re: I can't burp the oil tank on my 912 UL. Could use some h |
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I'm back to admit my sin. I was doing all this with one plug removed from each cylinder. Bob Borger just straightened me out and do I feel dumb.
Moving on, if I may. Ross I'll try the hold method that you're talking about. It sounds less strenuous. Even with the plugs out it was killing me…….Geoff
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Dual controls. Dynon 180. Icom 210 Garmin 296. Becker transponder. Sigtronics intercom. Electric flaperons. |
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dashwood
Joined: 24 Jan 2009
Posts: 73
Location: sw ontario canada
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moosepileit
Joined: 10 Dec 2007
Posts: 26
Location: USA
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| Posted: Wed Nov 24, 2010 7:15 am Post subject: Re: I can't burp the oil tank on my 912 UL. Could use some h |
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Once you are happy with the connections, don't forget that you are also probably near the stage where you want to do a purge per the service instruction. SI-912-018
This will include removing the valve covers, taking each piston to TDC and then checking each lifter for air by pressing 15# of pressure for 3 seconds on each pushrod. You then use a feeler gauge (.020/.5mm) to make sure there is no gap in excess of this under the valve springs at the top of the valves.
The rotax owners site has videos on this and I assume it's in the Lockwood 912 DVD also. Failing to do it will overload your valve spring retainers if not damage a running engine in general.
I made my own kit, though they are sold at Lockwood, CPS and LEAF.
You connect the oil vent line to 6-15 PSI, 15 is the max. Air will leak at the oil tank cap seal, but it's in the service instruction that it is normal. you put a plug on the return fitting to the tank, the one that you disconnected the oil return line from- I just used some short tubing lengths w/ AN plugs clamped in.
The Suction line to the oil cooler that then goes to the oil pump from the tank stays connected. The return line to the tank from the banjo is put low in a catch- you have good oil that you want to save, use a clean catch. You remove the spark plug leads, all 8, and remove the top spark plugs. Clockwise rotation of the prop by hand or with starter in 10 second bursts (then cooling) with good oil pressure indicated. Don't let the supply oil tank empty below the suction pickup tube or you introduce air and have to start over again after topping off the oil. I did it by hand and it worked just fine to get oil pressure up.
Reconnect the return line, disconnect the connection to the tank vent.
My pressure fitting from my air compressor w/ a 6 gal tank was a barb connection threaded into an air tank quick disconnect.
You are removing air from the system and making sure your lifters have no air in them.
There are some good threads on this here. This is also a good time to remind you that normal aircraft mechanics may not understand the engine at all. Unlike a Lyc or Cont engine, the case is supposed to pressurize to remove the need for a suction return pump. This is what you are doing when you burp the tank normally in preflight.
When you break the lines or are just starting out, you need to do the purge to remove air, then check your lifters per the SI.
http://forum.matronics.com/viewtopic.php?p=170780&sid=94250a8a2fb91b49bf1b932ea12247ae
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