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#3 Cylinder runs very hot after overhaul


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Just now, takair said:

What rings do you have?  Steel cylinders run chrome rings, but you don’t want those running in a chrome cylinder.  Also, did they confirm ring gaps?  Too tight and they will run hot and/or break.  Apologies if this was covered previously.

Thank you for that information and it was not covered previously so I appreciate it.  I know they confirmed the gaps and checked the rings when they removed the cylinder but I heard nothing about what type rings they were.  I will check on that today.  Thanks.

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11 minutes ago, takair said:

What rings do you have?  Steel cylinders run chrome rings, but you don’t want those running in a chrome cylinder.  Also, did they confirm ring gaps?  Too tight and they will run hot and/or break.  Apologies if this was covered previously.

I just checked with the mechanic.  They are not chrome rings.  The gaps were fine as well.

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Any chance the cylinder is running leaner than the other cylinders? A leak in the intake system, or something that will cause uneven dispersion of the air/fuel mixture?

The August Kitplanes, the editor had an overheating cylinder, #4 on a Glassair. Lean cylinder. 

 He tracked it down to the carb heat flapper not fully closing.

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7 minutes ago, Skydancer2992 said:

Any chance the cylinder is running leaner than the other cylinders? A leak in the intake system, or something that will cause uneven dispersion of the air/fuel mixture?

The August Kitplanes, the editor had an overheating cylinder, #4 on a Glassair. Lean cylinder. 

 He tracked it down to the carb heat flapper not fully closing.

Well, they did pressurize the intake system and found no leaks.  Not sure about the carb heat.  Interesting about the lean cylinder.  Looking at the EDM 900 data from the last flight, the #1 and #3 EGT's were 100 degrees warmer than the #2 and #4.  As you know the #1 and #3 are on the same side of the engine.  When I did the lean find from ROP on the EDM 900, the #1 cylinder was first to peak.

I wonder if there is something that would cause the 2 cylinders on the same side to run 100 degrees warmer on the EGT's or if that is even an issue.  Just thinking out loud.

 

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Two other thoughts.  Have they checked mag timing?  While it would affect all cylinders, a few degrees might get you below 400 on number 3.  Another thing to look at with a new jug is the valve clearance.  Sometimes need to swap pushrods to get the clearance correct.  While I can’t explain high CHT as easily as an EGT anomaly, it might be worth asking.

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20 minutes ago, takair said:

Two other thoughts.  Have they checked mag timing?  While it would affect all cylinders, a few degrees might get you below 400 on number 3.  Another thing to look at with a new jug is the valve clearance.  Sometimes need to swap pushrods to get the clearance correct.  While I can’t explain high CHT as easily as an EGT anomaly, it might be worth asking.

They did say the timing was correct.  I will talk to them about the clearance and the pushrods.  Thanks very much.

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Tighter tolerances can do that - air cooled engines need less tighter tolerances to cool better, not sure if the chromed cylinder would run hotter or be too slick to keep the oil where it needs it but, tighter tolerances could scrape more oil off and thus not cool as effectively.  It also may need to get past 50 hrs of run in before things settle down. When I did my o-320 I flew it about 50 hrs before it finally settled down. If your certain it's not 'lean', may just want to put hours on it at night around the airport traffic pattern. I flew mine at 4 am in the pattern at 2500 rpm - just announced I was not landing and stayed up about 500 over TPA letting everyone know where I was and I was breaking in a new engine. Staying over the airport gave me an out if I had issues... 

-Don 

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It sounds to me like you've done your diligence here and it's just gonna do what it's gonna do.   I'd just keep an eye on it and make sure it never hits the magic 500F number, and hope maybe it wears in or something and starts to cool off on its own.   It might fix itself in time, or it might get worse and make it more obvious what's going on.

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33 minutes ago, hammdo said:

Tighter tolerances can do that - air cooled engines need less tighter tolerances to cool better, not sure if the chromed cylinder would run hotter or be too slick to keep the oil where it needs it but, tighter tolerances could scrape more oil off and thus not cool as effectively.  It also may need to get past 50 hrs of run in before things settle down. When I did my o-320 I flew it about 50 hrs before it finally settled down. If your certain it's not 'lean', may just want to put hours on it at night around the airport traffic pattern. I flew mine at 4 am in the pattern at 2500 rpm - just announced I was not landing and stayed up about 500 over TPA letting everyone know where I was and I was breaking in a new engine. Staying over the airport gave me an out if I had issues... 

-Don 

Thanks Don.  It is possible that it needs more time.  I thought on average chrome cylinders broke in faster.  But when they pulled the cylinder again recently, the cylinder overhaul guy said that there were no issues with the cylinder but it looked like it was not completely broken in. I just got this information from a phone call a few minutes ago.  I was not sure if you could tell the break in status by visual inspection.  I know that oil usage, etc...is a way to help tell how the break in is going but I was not sure you can tell by visual inspection. 

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Just now, EricJ said:

It sounds to me like you've done your diligence here and it's just gonna do what it's gonna do.   I'd just keep an eye on it and make sure it never hits the magic 500F number, and hope maybe it wears in or something and starts to cool off on its own.   It might fix itself in time, or it might get worse and make it more obvious what's going on.

Thanks Eric.  I think this is where I am right now.  It was good to hear that when they pulled the cylinder all looked good.  So I am going to keep flying it and see what happens; famous last words. :D  I have posted this here and also sent an e-mail to JPI amongst others just to see if I am missing something, anything.

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Greg,

I will be baffled if this isn't baffling. In a C/D/E this is super critical and assuming all is good with the engine, and that is not a reach since it was rebuilt, the only thing else that changed was the baffling. I don't know if you still have a DH or not, but even a missing screw or gap can cause issues. Just my 2¢, hope you get it worked out.

--Harley

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Just now, HRM said:

Greg,

I will be baffled if this isn't baffling. In a C/D/E this is super critical and assuming all is good with the engine, and that is not a reach since it was rebuilt, the only thing else that changed was the baffling. I don't know if you still have a DH or not, but even a missing screw or gap can cause issues. Just my 2¢, hope you get it worked out.

--Harley

Thanks Harley.  We have been over the baffling multiple times and can't find anything with it.  All holes are filled and it seems like it was put together correctly.  But I will take another look at it.

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2 hours ago, Greg Ellis said:

Thanks Harley.  We have been over the baffling multiple times and can't find anything with it.  All holes are filled and it seems like it was put together correctly.  But I will take another look at it.

On the thought of baffling, the “wings“ that are on the outboard upper side can be troublesome.  I think they originally slipped under the vertical pieces Where they were bent, but many are screwed over the top.  If they are not secure enough, they will look fine but the pressure in the dog house will cause the edges to lift and bleed lots of cooling air.  If you are willing to expose your engine to us and our critique, can you post some pictures of the install.  Sometimes someone can pick up something that is not immediately obvious in words.  

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3 hours ago, Greg Ellis said:

Thanks Harley.  We have been over the baffling multiple times and can't find anything with it.  All holes are filled and it seems like it was put together correctly.  But I will take another look at it.

One often overlooked area is just behind and under the #3 cylinder at the oil pressure adjustment.  It takes some work with aluminum and rubber baffling material, but it can be sealed up pretty tight.

The other most often overlooked areas are where the doghouse goes around the upper engine mounts.

The most common area for holes are at the front around the starter and generator, and around the lip of the cowling- but it sounds like you already got those done.

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+1 for pics of the dog house...

+1 for posting any new data from the JPI... warm temps probably aren’t helping any...
 

Chrome is a very hard material... break-in requires wearing of surfaces... hard materials don’t wear very easily...

How many hours has this chrome cylinder accumulated?

Break-in for some cylinder and ring combinations can take  a really long time time...

Best regards,

-a-

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5 hours ago, carusoam said:

+1 for pics of the dog house...

+1 for posting any new data from the JPI... warm temps probably aren’t helping any...
 

Chrome is a very hard material... break-in requires wearing of surfaces... hard materials don’t wear very easily...

How many hours has this chrome cylinder accumulated?

Break-in for some cylinder and ring combinations can take  a really long time time...

Best regards,

-a-

Thanks for the responses.  I will get some photos of the baffling when I go back out to the airport later this week.  

The cylinder has about 28 hours or so on the break in.  When this first started happening I thought it was because it was new and during the break in it would run hot but I was told by multiple mechanics that 470 is too hot even for the break in.  JPI basically says that the EDM 900 is functioning properly so the problem is somewhere else. Savvy aviation has analyzed multiple flights and I get differing ideas from them. I appreciate the responses though and I am looking into all of their suggestions.  They have been very quick to respond to my inquiries and well worth the subscription to their analysis program.

What is the easiest way to post the data form the JPI on this forum?

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36 minutes ago, Greg Ellis said:

This was my most recent flight for about an hour.

IMO it is either break-in (i.e., take it easy until it settles in) or baffling. I came on here this morning to suggest you consult Mike Busch, but you beat me to it :P

Hang in there (and take it easy on climb until resolved).

Oh, what about engine mount alignment?

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7 minutes ago, HRM said:

IMO it is either break-in (i.e., take it easy until it settles in) or baffling. I came on here this morning to suggest you consult Mike Busch, but you beat me to it :P

Hang in there (and take it easy on climb until resolved).

Oh, what about engine mount alignment?

The engine mount alignment seems to be correct.  It is a new engine mount and the engine seems to be positioned correctly.  At least 2 different mechanics have looked at it.

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Verify what CHT sensor you have, and where it is located...

Some ship’s CHT gauges have been swapped for various types of thermocouples and put in less than ideal locations...
 

Look for one under the spark plug, a TC gasket...
 

This is an oddity that doesn’t get noticed... but the spark plug location is about 50°F hotter than the usual location...

Best regards,

-a-

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So, is the cyl. overhauled - not new, correct?  And why an OH stud assembly as opposed to new?  Was just oil consumption the problem?  The piston is original, vs new?  What you have changed is cyl. wall plating and rings - only.  Did the cyl. shop do all of the work - clean /check the piston, fit the new rings, send you back a complete assembly?  To me .. cleaning piston ring grooves is not worth the price of a new piston - they are the most reasonably priced piece of the whole assembly.  Simply checking ring gaps by fitting  a ring down in the cyl. then assembling on an old carboned up piston may be giving a false indication of fit.

Did you fit the piston pins yourself?  Did you put new pin plugs in?  How did the pin feel in the rod end?

Have you bore scoped the cyl?  Checked to see if any scoring is going on.  

I'd be cautious with continued flying.

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14 hours ago, mike20papa said:

So, is the cyl. overhauled - not new, correct?  And why an OH stud assembly as opposed to new?  Was just oil consumption the problem?  The piston is original, vs new?  What you have changed is cyl. wall plating and rings - only.  Did the cyl. shop do all of the work - clean /check the piston, fit the new rings, send you back a complete assembly?  To me .. cleaning piston ring grooves is not worth the price of a new piston - they are the most reasonably priced piece of the whole assembly.  Simply checking ring gaps by fitting  a ring down in the cyl. then assembling on an old carboned up piston may be giving a false indication of fit.

Did you fit the piston pins yourself?  Did you put new pin plugs in?  How did the pin feel in the rod end?

Have you bore scoped the cyl?  Checked to see if any scoring is going on.  

I'd be cautious with continued flying.

I did not do any of the work.  It was done by a shop here at my airport.  The cylinder was overhauled, not new.  In previous posts I mentioned that it has been borescoped and everything looked fine.  After continued flying they then removed the cylinder and visually inspected it and the piston and the rings and anything else they could see and all looked great including the cylinder and walls.  No signs of any damage, scoring or anything.

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On 6/23/2020 at 4:45 AM, Greg Ellis said:

Thanks. Well, you know how sometimes things are so obvious you look right past them.... :D

This was my most recent flight for about an hour.

https://apps.savvyaviation.com/flights/4066117/a8683e95-5833-400c-8064-551631c2e329

Something is causing your #3 EGT to be out of line and much hotter than the other cylinders on takeoff.

03242AB6-0DD7-4FDD-A8F6-2672297FAAA2.thumb.png.22ada936250453f11051fbb023144ddb.png

 

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