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JonathanMilbank
Joined: 14 Apr 2012
Posts: 390
Location: Aberdeen area
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 Posted: Tue Aug 16, 2022 5:13 am Post subject: Topic deleted |
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Topic deleted
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Last edited by JonathanMilbank on Tue Aug 16, 2022 12:06 pm; edited 4 times in total |
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Rocketman
Joined: 07 Sep 2010
Posts: 87
Location: USA, Earth
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| Posted: Tue Aug 16, 2022 7:35 am Post subject: Excessive oil consumption |
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My money would be on the oil seals at the valves, however, There is
always the possibility, though remote, of a cracked head. Easiest way
to narrow it down is to remove the exhaust down pipes and have a peek
inside. If you've got oil going through one cylinder, you should be
able to verify it by looking. If all pipes show evidence of oil, then
it's probably seals. Just a thought.
Jeff,
N55XS - Baby Blue
On 8/16/2022 8:13 AM, JonathanMilbank wrote:
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My 912ULS was bought 2nd hand after being stripped and rebuilt, following an accident in a foreign airframe. I have no record of how long it operated since new and my logbook starts at 220 hours, continuing from early 2014 and the subsequent 8.5 years until now to log another 470 hours.
However I've become aware of gradually increasing oil consumption in the latter years up until now, when I'm using 1.5 litres per 50 hours. As I recall, originally the consumption was less than 0.5 litre. There is a brown stain emanating from the exhaust and continuing under the port wing along the rear fuselage.
The most plausible explanation so far is that the valve stem oil seals have stiffened with age and should be replaced. This is something which I potentially could do, having previously removed a cylinder head and lapped the valves, resulting in fully restored compression for over 150 hours. All 4 cylinders are within 3 psi of each other to this day and the engine performs as well as ever.
There are no other oil leaks from the engine and the breather collection pot barely fills at all. The spark plugs show no signs of oiliness. But I'm contemplating that I might eventually remove all 4 heads and give them to an expert for a proper refurbishment, once it reaches a point where I don't want to see the brown streak on the port side any longer.
So to the point of this email. I definitely have no intention of removing the cylinders and pistons to check oil rings. Why? Because to the best of my knowledge the Rotax 912 engines are very high quality, to the extent that I've never read nor heard of cylinders, pistons and rings being badly worn with barely 700 hours of operation. I'm very willing to "take the chance" that only the cylinder heads need refurbishment. So unless I see scoring of a cylinder wall after head removal, I'll "let sleeping dogs lie." No honing, etc.
If I'm wrong and the head refurbishment isn't enough to cure the oil problem, then it won't be too awful to remove everything and start again.
My question is whether anyone knows of excessive cylinder, piston or ring wear in an engine with only 700 hours, not due to human error like using the wrong oil or losing coolant, or anything that contradicts my faith in Rotax.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=507684#507684
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