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jkuehn(at)mountaintime.my
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 Posted: Fri Jun 30, 2006 6:39 am Post subject: Burning oil |
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My 912UL has started to burn oil. I changed the oil at 50 hours, and it
had burned about half a pint in the first 50. At 63 hours it had not
burned any significant amount. Now I am on a long cross country, and it
burns through the acceptable range on the dip stick in about 7 hours.
Most of a quart between 63 and 76 hours. I am using Mobile1 MX4T.
Engine temperatures are normal, even though it is hot out (mid 80's to
mid 90's F) and the engine has good power, runs smooth, everything else
seems normal. No leaks. Anybody have experience with this?
I tried to call Lockwood at their tech support number, during advertised
hours but they do not answer!!
Jack
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Darryl Braun
Joined: 05 May 2006
Posts: 4
Location: Cold Lake
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| Posted: Fri Jun 30, 2006 7:54 pm Post subject: Burning oil |
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Hey Jack
Do you have any residue on the bottom of the plane where the exhaust flows?
If it's burning that much oil there should be a sooty or oil residue on the
plane, or the prop if it's a pusher. That would only confirm that the oil
is being burned of course. After that you'd do well to have a look at the
plugs and see if you can isolate one cylinder or one side of the engine.
Maybe a differential compression check as well. If you're going through
that much oil that fast I would suspect a broken set of piston rings or a
lack of crankcase ventilation causing high pressure air in the crankcase to
blow past the rings and carry oil with it. The Rotax vents through the oil
tank though, so if the oil is returning to the tank then I would think that
the ventilation is good. Other than that the only thing I can think of is a
burned valve in combination with a bad valve seal. To be honest I don't
even know if Rotax has valve stem seals, since it's flat 4 engine the oil
wouldn't really be able to flow down through the valve guides and on the
valve.
Hope that helps some. I am not a mechanic by any means though and there are
probably a lot of people out there who are going to set me straight on a few
of these ideas. But, at least that would get some good conversation going.
Good luck with the engine Jack
Darryl Braun
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_________________
Darryl Braun
94 Pelican PL #583, C-GGVS
Rotax 912 |
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Sat Jul 01, 2006 3:22 am Post subject: Burning oil |
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Jack,
How many hours on the engine? Are there any new noises in the engine?
Does power seem to be normal? Has the fuel burn rate changed since the
increased oil consumption began?
As Darryl said, check for oily exhaust output, plugs and do a
differential pressure check to isolate the source of the problem.
Sometimes rings turn in a cylinder and the gaps line up temporarily
which will allow oil to pass until they misalign again.
FYI - The intake valves on the 912 series do have valve stem seals but
the exhaust valves do not.
Thom in Buffalo
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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daveaustin2(at)can.rogers
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| Posted: Sat Jul 01, 2006 3:47 am Post subject: Burning oil |
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Have you investigated the Rotax service tip re possible cracking of the
crankcase in three specific locations?
That would explain the sudden oil use.
Dave Austin 601HDS - 912, Spitfire Mk VIII
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JetPilot
Joined: 10 Jan 2006
Posts: 1246
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| Posted: Sat Jul 01, 2006 9:06 am Post subject: Re: Burning oil |
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I was wondering the same thing, why are you so sure it is being burned ? Chances are just as good if not better that is it leaking the oil out somewhere.
Michael Bigelow
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"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
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jkuehn(at)mountaintime.my
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| Posted: Sat Jul 01, 2006 10:58 am Post subject: Burning oil |
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Thank you for all your replies. I appreciate all the knowledge. I
finally was able to talk with the tech support at Lockwood, and this was
very helpful. They say that these 912's "never" burn oil. It is rare,
and even when compression is low on a run out engine, they still do not
burn oil. So this leaves a leak, or my own confusion over the ever
moving target of oil level! It comes as no surprise to me that a hot
engine will show a different oil level than a cold one, even using the
technique of pulling the prop through. This can be compounded by the
particular oil system installation. I have an oil thermostat installed
on top of the engine above the sump can. The cold engine did indicate a
higher oil level, so my estimate of the quantity of oil burned was too
high. I do not have a plugged blow tube, and I do collect this stuff in
a small container. It never has more than a small amount and is just
oily water. The engine runs completely normally. He asked me what my
static full power RPM is, and I said about 5000. I was told to flatten
out the prop until I get 5500, and that I am essentially lugging this
engine, which will cause some soot and perhaps some oil burn. In fact
my plugs have been a bit on the sooty side. He made the analogy of a
Volkswagon pulling a heavy trailer, lugging like crazy. So I have made
the adjustment, and run up the engine, and wow there is a big difference
in power. He said I will be amazed! I have not flown yet because the
weather is not cooperating here! But I think all is well. I am flying
a Sky Ranger, a tractor. It is a good little plane with great
performance with this engine. My fuel burn was closer to 3.2 gallons
per hour for the 13.5 hour trip, which will change now with the new prop
adjustment. I think it will go up, but so will my speed, perhaps. The
plane handles really very well and for a 610 LB plane it handles cross
wind landings admirably.
I will let you know what happens.
Jack
JetPilot wrote:
| Quote: |
I was wondering the same thing, why are you so sure it is being burned ? Chances are just as good if not better that is it leaking the oil out somewhere.
Michael Bigelow
--------
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=44164#44164
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jnjkimbell(at)hotmail.com
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| Posted: Sat Jul 01, 2006 12:18 pm Post subject: Burning oil |
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Jack, I just changed the pitch on my prop to increase the rpm to 5600 Static
rpm on my CH701. I will now take off in almost one half the length, but I
think you will find as I did that it will show a slower IAS. It like a boat
prop. Less pitch, more power less speed, More pitch less power, more speed
at same RPM
---
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