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  #11  
Old 12-26-2017, 11:46 AM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by Aluminum View Post
What are the conditions to watch out for where glazing would occur?
Continuously High CHT's during break-in. I'm not talking the higher CHT's DUE to break-in - but something up in the 450 range.
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  #12  
Old 12-26-2017, 02:39 PM
Canadian_JOY Canadian_JOY is offline
 
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And to build on Paul's comments, glazing of cylinders often manifests itself through oil consumption which does not plateau after a reasonable number of hours of break-in time. That and low compression, if one takes the time to do a compression test.

With reference to my comment previously quoted, our oil consumption rate is not consistent with glazing, and our CHT's are well below the limits previously discussed on this forum by Mahlon Russell as being associated with causing glazing.
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  #13  
Old 01-14-2019, 11:02 AM
Aviaman Aviaman is offline
 
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Default Engine break in again

I have a Lycoming o-360 with about 60 hrs. Oil consumption is high-about a quart every 4 hrs. It seems to all be going out the breather tube. And, no, I am not over filling. At just 6 or 5.5 qts, it still uses oil rapidly. I suspect the rings have not properly seated, possibly due to glazing. I bought the plane with about 40 hrs on it, so I donít know what itís break-in process was. I have been using Aeroshell 15W50, not mineral oil, after initially assuming break-in was done. The cylinders are nitride I think. It may have been run at excessive CHTs during break-in, causing glazing. I am about to do a borescope and compression test. My question is what to do, assuming glazing has occurred. Would going back to mineral oil do anything, or is it too late if already glazed? Are there any other possibilities than glazing?
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  #14  
Old 01-14-2019, 11:47 AM
lr172 lr172 is offline
 
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Glazing is caused by heat and a thicker than normal coating of oil on the cyl walls. Before the rings have seated, there will be a thicker than normal coating of oil on the cylinder walls. If this thick coating of oil is exposed to heat above the critical level, it will oxidize and glazing occurs, halting the break in and causing high oil consumption. I cant give exact numbers, but it is near the 450* level. It is a bit variable, as the critical temp is measured on the barrel wall, and that temp does not move in a linear fashion with the CHT in rising or declining temps. Once the rings seat, the thinner oil layer is pretty much resistant to glazing, even above 450*.

During my O-320 break in, I let two cylinders get to the neighborhood of 450 for about 15-30 seconds before noticing it. Both cylinders were glazed and required a re-hone.

It is purely a heat issue and it doesn't take much time to do it.

Larry
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Last edited by lr172 : 01-14-2019 at 11:50 AM.
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  #15  
Old 01-14-2019, 11:54 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Aviaman View Post
I have a Lycoming o-360 with about 60 hrs. Oil consumption is high-about a quart every 4 hrs. It seems to all be going out the breather tube. And, no, I am not over filling. At just 6 or 5.5 qts, it still uses oil rapidly. I suspect the rings have not properly seated, possibly due to glazing. I bought the plane with about 40 hrs on it, so I don’t know what it’s break-in process was. I have been using Aeroshell 15W50, not mineral oil, after initially assuming break-in was done. The cylinders are nitride I think. It may have been run at excessive CHTs during break-in, causing glazing. I am about to do a borescope and compression test. My question is what to do, assuming glazing has occurred. Would going back to mineral oil do anything, or is it too late if already glazed? Are there any other possibilities than glazing?

You can see glazing directly through the sparkplug hole with a flashlight. Shiny metallic color indicates no glazing. An opaque yellowish, tan color on the walls is glazing. 100% glazing is uncommon. You will usually have patches or areas of glazing with other parts un-glazed. Glazed cylinders will typically show oil pooling at that piston and wet, oily plugs. Glazing typically does not negatively impact compression.
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Last edited by lr172 : 01-14-2019 at 11:58 AM.
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  #16  
Old 01-14-2019, 12:31 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Aviaman View Post
I have a Lycoming o-360 with about 60 hrs. Oil consumption is high-about a quart every 4 hrs. It seems to all be going out the breather tube. And, no, I am not over filling. At just 6 or 5.5 qts, it still uses oil rapidly. I suspect the rings have not properly seated, possibly due to glazing. I bought the plane with about 40 hrs on it, so I donít know what itís break-in process was. I have been using Aeroshell 15W50, not mineral oil, after initially assuming break-in was done. The cylinders are nitride I think. It may have been run at excessive CHTs during break-in, causing glazing. I am about to do a borescope and compression test. My question is what to do, assuming glazing has occurred. Would going back to mineral oil do anything, or is it too late if already glazed? Are there any other possibilities than glazing?
Before doing anything else, I suggest you stop using the multigrade oil and switch to Aeroshell 100 (straight mineral), and see what happens.
Whether it gets better or not, I would recommend you not use the multi weight.
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  #17  
Old 01-14-2019, 12:50 PM
jabarr jabarr is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Before doing anything else, I suggest you stop using the multigrade oil and switch to Aeroshell 100 (straight mineral), and see what happens.
Whether it gets better or not, I would recommend you not use the multi weight.
Why? Where’s the data to back up that statement?
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  #18  
Old 01-14-2019, 01:02 PM
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rocketbob rocketbob is offline
 
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The only way to fix glazing is to rehone the cylinders.

Contrary to popular belief cylinders break in seconds and minutes, not hours of "running hard".

Overhaul an engine and put your ear on a cylinder while pulling the prop thru, then run it once. Big difference how it sounds.

Keep initial runs short and under 300 CHT. Let it cool completely before a subsequent run. I've never had an engine use oil after an overhaul doing breakins this way.
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  #19  
Old 01-14-2019, 01:11 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by jabarr View Post
Why? Whereís the data to back up that statement?
Personal conversations with engineers and regional reps from Lycoming.
Based on what I have been told, I do not use Aeroshell multi weight in our fleet of airplanes.
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  #20  
Old 01-14-2019, 02:16 PM
jrs14855 jrs14855 is offline
 
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Default Break in

Phillips XC 20w50 has become widely used for break in in recent years. The goal for break in should be to keep the CHT below 400. A very momentary excursion to 425 should not cause a problem.
Mahlon Russell has a ground run and flight profile for break in which I followed to the letter with excellent results. I believe it can still be found on Lycoming yahoo forum.
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