Overheating Cylinder Effects

MBDiagMan

MBDiagMan

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I went through a period of an overheating cylinder on an IO360. It ran real close to 450 degrees several times for brief periods before noticed and dealt with. It was analyzed and they couldn’t find the problem, then it magically fixed itself. Probably an injector cleared or something. Temps on all cylinders began running around 380 or 390. When the hot cylinder problem existed, it might have made it slightly hotter than 450 a few times.

Okay, progressing forward to annual. There was a little metal in the filter, but all cylinders had pretty strong compression. The plan is to put ten hours on the oil change and drain it again for an oil sample and cut the filter again.

I forgot to mention that they pulled the copilot side rear cylinder to inspect and everything looks good, but the overheating cylinder was number three on the JPI whichever cylinder that is. I forgot about the previously overheating cylinder or I would have asked them to pull that one.

So, what are the chances that the hot cylinder made the metal?
 
MBDiagMan said:
I went through a period of an overheating cylinder on an IO360...I forgot to mention that they pulled the copilot side rear cylinder to inspect and everything looks good, but the overheating cylinder was number three on the JPI whichever cylinder that is. I forgot about the previously overheating cylinder or I would have asked them to pull that one.

So, what are the chances that the hot cylinder made the metal?
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Mooney M20F? That would be a Lycoming engine. @Isosceles in the post above is correct; they pulled cylinder #3.
 
Okay guys. It helps to know that they pulled the cylinder that had been hot. At least number three is what was shown hot on the JPI, so if it is wired correctly to the JPI, then they pulled the hot cylinder.

Honestly, I would be thrilled if it turned out that the metal came from a cylinder. A new cylinder costs a pittance as opposed to a complete tear down.
 
Is making metal is a result of a cylinder getting too hot?
 
The strength of the metal it’s weaker at the higher temperatures, but That doesn’t mean it’s suffered damage. Did this happen on takeoff when you’re running the engine 75% or better? At worst you’ll need to replace the cylinder, but I would borescope it and if looks OK just keep running it.
 
Okay, thanks to responses here, I now fully expect that the cylinder that was removed for the purpose of allowing internal engine inspection was the cylinder that had run hot. It looked good, so that probably answers my original question which was “ could the previously overheating cylinder have been responsible for the metal.

if the metal had been the result of that cylinder overheating I would be tickled to death because replacing the cylinder would be cheap as opposed to a complete tear down.
 
Have you read the guidance published by Lycoming on type and amounts of metal found in a filter? A good read that may settle your nerves some. Absolute redline on a Lyc cylinder is 500 deg. 450 isn't good, but it shouldn't be catastrophic. What did your borescope/wall /valve look like? Sure it wasn't the probe?
 
Lycoming manual for the IO-360 A- series states an absolute CHT max of 500*, and for maximum service life to limit CHT to 400*. We have our JPI set to flash at 390, and I take action if it reaches 400.

Seeing this, I think you're fine.
 
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I didn’t see mention of oil analysis. This can help determine where the metal came from.
 
Yes, I think I wrote that I plan to fly it ten hours, then cut filter again and do oil analysis.

The cylinder was removed so that the engine could be inspected internally. Everything looked good including the cylinder and piston.
 
Check for the presence of the inter-cylinder baffling between cylinders 1 and 3. It is often missing. Your A&P should know what it is.
In the engine photo below, the bracket on the cylinder fins between the push rod tubes holds the inter-cylinder baffling tight to the bottom fins directing the air BETWEEN the fins.
Engine.Crated.Crop.jpg
 
450* for a short time isn't a problem. In itself that wouldn't cause metal failure but metal failure can cause high temps.
 
Almost sounds like a partially blocked fuel injector or intake leak to me
 
Thanks for the continuing information. I think I wasn’t clear with my question and description.

For several months, number three cylinder on the JPI bar graph would run about 60 degrees hotter than the other three. A couple of months ago it corrected itself and began running as cool as the other three, always below 400. THEN annual came along and in the course of it there was metal in the oil filter. Tiny little shiny flakes on the pleats and a small amount rinsed out that could be moved with a magnet.

For the last several months before the annual there was no hot cylinder, but my original question was: Could that cylinder being hot for a while be the cause of the metal in the filter?

The cylinder temps, oil pressure and everything are running very nicely now. To fly it and monitor all the vitals now, you would never know there had ever been anything awry.
 
Without knowing what type of metal it is there is no way of knowing where it came from
 
It's common with 4 cylinder Lycomings to have #3 run hotter. My own #3 is my warmest cylinder, too. Even after building a ramp in front of #1 it remains the warmest. The way Lycoming cylinders are cast there's no airflow through the fins on the back of #3 so there should be a stand-off to space the rear baffle away from the cylinder, but even that isn't a perfect solution. Why the change in temp? Good question, but I doubt is has anything to do with the metal.

Did EGT run high at the same time the CHT did? Has that changed?
 
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unsafervguy said:
Without knowing what type of metal it is there is no way of knowing where it came from
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Yes, that’s why we are running it ten hours then doing oil analysis. What I am seeking here is whether or not a 450+ degree cylinder might have shed the metal.
 
Where are the probes located and how old are they?

I went through a period of time where JPI probes would only last 500 hours or so.

Also, there will be a temp difference between threaded probes in the probe-ports and the spark-plug gasket probes.
 
MBDiagMan said:
Yes, that’s why we are running it ten hours then doing oil analysis. What I am seeking here is whether or not a 450+ degree cylinder might have shed the metal.
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You said the suspect jug was removed, inspected and no defects found. Piston and rings look good too? I have heard suspect stories that it's possible channel chrome cylinders might flake, but if you've got steel jugs then n/a. Given no visual evidence, I can't see how a 450 temp could cause the jug to be the source of the metal. Lack of lubrication would be self-evident on inspection. Tiny little shiny flakes in the pleats are generally cam or follower starting to spall, but if the amount is very small then following Lycoming guidance is the right course of action, and again, that's not dependent of cyl temp. How did your oil temp behave during this period?
 
wsuffa said:
Where are the probes located and how old are they?

I went through a period of time where JPI probes would only last 500 hours or so.

Also, there will be a temp difference between threaded probes in the probe-ports and the spark-plug gasket probes.
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The JPI and it’s probes was installed two years ago. The cylinder is running the same temp as the other ones now. I believe the problem was a partially blocked injector that cleared. The cylinder is no longer hot. My question is whether or not it would be possible that the cylinder could have made the metal when it was running hot.
 
Chip Sylverne said:
You said the suspect jug was removed, inspected and no defects found. Piston and rings look good too? I have heard suspect stories that it's possible channel chrome cylinders might flake, but if you've got steel jugs then n/a. Given no visual evidence, I can't see how a 450 temp could cause the jug to be the source of the metal. Lack of lubrication would be self-evident on inspection. Tiny little shiny flakes in the pleats are generally cam or follower starting to spall, but if the amount is very small then following Lycoming guidance is the right course of action, and again, that's not dependent of cyl temp. How did your oil temp behave during this period?
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Great reply Chip! Thanks very much!

The cam and lifters looked great in the inspection except for one line across a cam lobe that appeared as a thin line of corrosion. The piston and rings looked good.

Some more history on the engine. It sat for a few years. When the reputable shop put it back in service they pulled the jugs and inspected everything, honed the cylinders and replaced the rings. That was about 150 hours and two years ago. The rings did not appear to be fully seated. The first annual did not reveal any metal, and I had done an oil and filter change at about fifteen hours after they did the inspection, hone and ring work, and there was no metal then. Also I don’t think I mentioned in the OP, but it was majored about a thousand hours ago.
 
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If it's aluminum flakes, common cause is piston pin plug and is harmless.
 
If it was a clogged or partially clogged injector nozzle would not the cylinder be running cooler not hotter? Bob
 
When clogged, an injector would have limited fuel flow which would result in a lean condition. A lean condition results in higher combustion temperature. I believe that the lean condition that magically corrected itself may have been a clogged injector that cleared out.
 
MBDiagMan said:
The JPI and it’s probes was installed two years ago. The cylinder is running the same temp as the other ones now. I believe the problem was a partially blocked injector that cleared. The cylinder is no longer hot. My question is whether or not it would be possible that the cylinder could have made the metal when it was running hot.
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Possible, yes. Likely? Maybe not as the compressions measured out and they didn't see anything when they pulled the jug.

I'd do what your doing: run it a few hours and do a compression check and oil analysis.

Any number of things it could have been.
 
MBDiagMan said:
When clogged, an injector would have limited fuel flow which would result in a lean condition. A lean condition results in higher combustion temperature. I believe that the lean condition that magically corrected itself may have been a clogged injector that cleared out.
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Please help me to understand better, but wouldn't that depend on how much the injector is clogged?
My thinking is that if the injector is slightly clogged, that cylinder would be leaned, and act as you describe. Clogged a bit more, and it starts running lean of peak with reduced temperature. The limiting condition to me is completely clogged, so no fuel, therefore the temperature is very low.

Thanks for your explanation.
 
As a follow up to this discussion:

After the oil analysis showed iron, the engine came apart. Two spalled lifters were the metal making culprits. Sent the cylinders to the cylinder shop, split the case, did the case and crankshaft and replaced cam and lifters. The cylinder shop called the cylinders “low time” after inspecting and micing. They were nickel, so they sent them to have the nickel tested and certified before reconditioning them. They were very pleased with the outcome which resulted in a zero time overhaul. I would have been agreeable to replacing them with new cylinders but they were pretty much unavailable.

The engine is now back together and we will probably run it today. I will post the outcome of testing
 
For future reference if you see a change in how your engine operates like a large change in CHT the time to investigate is before the next flight. If you had a partially clogged injector you would have had a big change in EGT but not so much in CHT.
 
Robert Markle said:
If it was a clogged or partially clogged injector nozzle would not the cylinder be running cooler not hotter? Bob
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Depends if you are running ROP or LOP.
If partially clogged running ROP may end up running higher.
 
I don’t understand how that can be. A lean condition will cause higher temp either way. The only difference might be that you are probably operating at a lower power setting if you’re lean of peak.
 
If you are lean of peak and you get an injector blockage, that cylinder would become more lean, lowering the EGT which would lower the CHT. ROP the blockage would most likely raise the EGT which in turn would raise the CHT.
 
A lean condition increases combustion temperature. Hopefully when you are lean of peak you are at a reduced power setting which would decrease temps, but a lean mixture alone does not.
 
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MBDiagMan said:
A lean condition increases combustion temperature. Hopefully when you are lean of peak you are at a reduced power setting which would decrease temps, but a lean mixture alone does not.
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The power decreases when leaning LOP because there is less fuel to burn, decreasing the energy (heat) in the cylinder which results in less power. Cirrus advertises further leaning as a method to control CHT when running LOP, I believe the number they use is approximately 1 degree decrease in CHT for every 10 degrees decrease in EGT, LOP.
 
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