Apparently there is a procedure for dissolving the stuff off, but nobody wants to talk about it openly.
Does anyone know what it is?
Peter wrote:
Apparently there is a procedure for dissolving the stuff off, but nobody wants to talk about it openly.
It is a very well known procedure and many (most?) A&Ps know it. I think Eugene discussed it on this forum before. There is nothing secret about it.
http://www.scribd.com/doc/254085919/Oil-Control-Ring-Solvent-Flush-Procedure-Ed-Kollin-CamGuard
It worked for my compression rings on one cyl and exhaust valve on the other. Not so good with my oil ring which is better but still not just right. A 50% improvement in oil consumption.
I think it should be done every 500hrs as a PM (Preventative Maintenance) item. That along with checking for valve wobble.
What effect does this have on the various other seals, especially the crankshaft seal?
We had this very discussion here: http://www.euroga.org/forums/maintenance-avionics/3451-need-help-finding-flush-products?page=3
You keep the sump open and when pushing the solvents by the rings, you hope it will not get in contact with the crankshaft seal.
Would you not see a difference in the condition of the spark plugs, if there was a lot of oil finding its way past the piston rings?
The reason I am interested in this is because I have seen a rise in oil consumption, from 1qt every 8-10hrs to 1qt every 5-6hrs, about 1000hrs after a total new-limits rebuild. The latter figure is still within airworthiness limits (by a factor of five!) but I wonder where the oil might be going.
There was an article on Mooneyspace a while ago about a sudden increase in oil consumption. The culprit was the prop shaft seal which had become a bit dislodged (or something to that effect) allowing the crankcase to pressurised by airflow while in flight.
Maybe worth checking.
If it’s due to pressurization (either through the crankshaft seal or more likely through the piston rings), the oil usually goes overboard quite rapidly leaving the traces and only down to a certain level.
Most likely it is due to piston rings sealing not as well as before. Oil consumption varies greatly among engines and does change over time. I currently have about 1/2-1qt in 25h (which is my oil change interval).
I currently have about 1/2-1qt in 25h (which is my oil change interval).
That is extremely low. It is of the order of 1/5 of the average for the engine.
I can’t dig out a reference right now but it is widely suggested, and makes good sense, that very low oil consumption means that the engine is not getting well lubed, and it correlates with sticky valves (which you had) and generally with the engine not making TBO.
A 25hr oil change interval is certainly a good idea. The oil only just barely makes it to 50hrs, if one looks at the oil analysis.
Peter wrote:
it is widely suggested, and makes good sense, that very low oil consumption means that the engine is not getting well lubed
Well, I do not believe that at all and have not seen anything of substance backing such a claim. More looked like poor attempts to justify the poor quality of the engines and turning a vice into a virtue.
Peter wrote:
and it correlates with sticky valves (which you had)
That wouldn’t make much sense at all. To the contrary, oil entering the combustion chamber (which is how a Lycontosaur loses oil during operation, apart from leaving through the crankcase breather) contributes to crud getting between valve and valve guide. Valves are a little bit cooled by oil flowing through the cylinder head but again, the more you lose (by burning), the more crud in the valve guides. So I would claim the opposite is true.
