High EGT on one cylinder (it's not the probe)

[KyleKJ90]

I must be going to bed but here's exactly what I sent to Lycoming yesterday. Sorry in advance for the lengthy comment but it's everything and anything in order that we've done. Hope this helps.

Hello Ryan,

I apologize for the delayed response. As we discussed the other day we're still getting a higher than normal EGT indication on our #2 cylinder. Looking over my borescope videos of the #2 cylinder I realized that I have more footage of the valves than the actual cylinder wall so they won't be of much use if I sent them. I'd like to enclose the engine monitor data for the particular flight where this issue first happened. It becomes very apparent that something has happened to the #2 cylinder around the 2 hour 21 minute mark.

https://www.savvyanalysis.com/flight/909290/0b7cfa44-4d8a-4fc1-8b1d-e351520276c0

The following flight after this one can be seen here and confirms the high EGT.

https://www.savvyanalysis.com/flight/909291/4081b956-abf9-4d21-8494-3e2b15460c1f

I can confirm that the engine monitor (JPI EDM 700) is working correctly as I have swapped both the probes and their respective channels of cylinders #2 and #4. The JPI confirms a hot EGT on the #2 cylinder and there doesn't appear to be any issue with the engine monitor. Just to confirm what all has been checked up to this point and in order of which they were done, I've listed all the items and their result below.

1. Cleaned fuel nozzles - No change noted

2. Swapped EGT probe from #2 cylinder to the #4 cylinder - No change noted

3. Attached #2 EGT probe wires coming from the JPI to the #4 cylinder and vice versa (The JPI showed the #2 EGT as cylinder #4 on the gauge. This was done to check gauge/channel for a fault.) - The result was a high EGT on the #4 indication on JPI.

4. Performed in flight induction leak check and in flight mag check. - No defects noted.

5. Installed a NEW EGT probe to #2 cylinder per other owner's request - No change noted

6. Cleaned fuel nozzles again. Cleaned, gapped and rotated spark plugs. #2 cylinder plugs looked oily compared to all the rest. - No change noted

7. Swapped fuel nozzles between #2 and #4 cylinders. Flow checked fuel coming from manifold tubes into containers. Fuel flow appeared to be even between each container for each cylinder. - No change noted.

8. Installed new intake gasket to #2 cylinder, inspected #2 intake tube lower o-ring. Pressure tested intake system with shop vac. - No leaks noted other than several pin holes in bellows gasket between fuel injection body and aircraft cowling/air box. No change noted during flight test.

9. Cleaned fuel injector body fuel inlet screen. Flow checked fuel flow indicator by disconnecting fuel line going to flow divider. (merely wanted to check accuracy of fuel flow indicator.) Small bubbles noted going through clear tubing during this check. Thought bubbles to be coming from AN union connecting clear tubing to aircraft fuel line that was only finger tight for my test. Regardless, air in the fuel system would most likely cause a different issue than what we're experiencing correct? At this time I also flow checked all the fuel manifold tubes in graduated containers for 2 minutes and the results were as follow. At a flow of 5.9 to 6.0 GPH, cyl #1 = approx 175ml; cyl #2 = approx 200ml; cyl #3 = 175ml; cyl #4 = approx 175ml.

Just on a side note, I happened to notice oil residue at the bottom of the #2 intake tube. It does not appear to be in the lower air chamber located just aft of the fuel injector body. Also, during each flight test the difference in EGT between the highest cylinder (typicallay #2 ) and the lowest (typically #1) increases with increasing manifold pressure. We don't see the high EGT issue on the ground or during the engine run up before takeoff. It's starts to show during the full power during takeoff and continues all the way until power is reduced for landing. During one of the last flight tests with mixture full rich and RPM at 2500, the following differentials in EGT were recorded.

15 inches MP = 80 degress diff

17 inches MP = 90 degrees diff

19 inches MP = 120 degrees diff

21 inches MP = 130 degrees diff

I hope all this information helps and if you still need borescope images from the #2 cylinder side walls I can obtain them yet this week. Our annual inspection is due at the end of this month and ultimately we would like to know what actions if any will need to be done as we've thoroughly gone over all the basic items and is proving to be rather frustrating. Could it be possible that our oil containment ring has cracked and oil is getting in to the cylinder causing this issue?

I look forward to hearing from you soon.

Kyle

[Marauder]

Kyle - it sounds like you have tried everything. Have you pulled or looked inside the inlet tube going to the cylinder and also the exhaust from the cylinder? Your flow test for #2 shows 14% more flow to that cylinder. Short of pulling the cylinder, air in and air out are the only other variables.

Sent from my iPad using Tapatalk

[KyleKJ90]

Keep in mind the measured fuel flow check was done with the nozzles disconnected. I was merely checking the flow divider and there's a small chance that the hangar floor wasn't perfectly even when I did this. :-/ I've borescoped the entire #2 intake tube through the injector threaded hole down to the area in the pan where the other intake tubes are. Nothing noted other than a puddle of oil down at one spot in the intake tube. I haven't borescoped the exhaust other than the exhaust valve and seat which I accessed through a spark plug hole.

[Piloto]

Kyle have you look into the inside of the muffler. A partial obstruction for the exhaust gases will reduce the exhaust flow thus increasing the temp. There are two internal tubes with holes inside. As the muffler ages these tubes can deform thus reducing the exhaust flow. Take the exhaust pipe out and check inside the muffler.

José

[KyleKJ90]

Muffler looks good inside. Couldn't snake the borescope in the spark plug hole and then through the exhaust port. I did stick the borescope up the tailpipe and both piccolo tubes appear undamaged and unobstructed. As usual, the cylinder and spark plugs look wet with oil. The intake valve seems to be wet with oil as well. That would explain the trace of oil down in the intake tube that I keep seeing with the borescope and perhaps our higher EGT. That's just one mans opinion here though. What do you guys think? Time for the wobble test on the valve/valves?

http://mooneyspace.com/gallery/image/36683-2-and-4-spark-plugs/

http://mooneyspace.com/gallery/image/36682-2-and-4-spark-plugs/

http://mooneyspace.com/gallery/image/36684-2-intake-valve/

http://mooneyspace.com/gallery/image/36685-2-intake-valve/

http://mooneyspace.com/gallery/image/36686-2-intake-valve/

[KyleKJ90]

I know it's been a while but after exhausting all the possible external causes for our high EGT issue, we finally took our bird to the engine shop. Our main reason for choosing to do so was a constant puddle of oil noted at the bottom of the intake tube and oily spark plugs. It's not burning enough oil to notice it on the dipstick but with the elevated EGT and CHT we decided it was time. I made one last call to Lycoming just to see what they thought and they agree that there's just enough oil getting into the cylinder from somewhere to be causing our issue. The question now though is WHERE. I'm hoping that it's from the scraper/oil control ring or perhaps a slightly worn valve guide and not a small crack somewhere in the cylinder head but time will tell. Fingers crossed we don't need a new jug   I'm supposed to be hearing from the shop sometime tomorrow and I'll be sure to let you all know what has been causing our issue. Thanks for all the suggestions and troubleshooting advice during this long and treacherous journey. Hopefully we'll have the old girl back up and flying by the end of the week!

 

-KJ

[KyleKJ90]

The results are in. For what it's worth guys, listen to your engine monitor. Our JPI was telling us that the exhaust truly was hot and as it turns out our #2 cylinder was out of round by .0045 inches. That's right at the serviceable limit per Lycoming but our engine shop trued up the cylinder to a closer tolerance than that and our issue is now GONE! I have no idea why it showed up so suddenly but I guess the increased tolerance allowed excessive amounts of oil get past the rings and into the combustion chamber during high RPM operations. We never saw an increase in oil consumption but the JPI told no lie; the exhaust really was hot. Keep in mind the cylinder peaked at the same time as it usually did when finding peak, only it was 150-175 degrees higher than normal. I can only assume running the cylinder like that for an extended period of time would have caused more headaches such as a burned valve or something along those lines. So in summary, listen to your engine monitor and if you rule out all the easy culprits like fuel, intake air and ignition, don't be afraid to pull the cylinder and have your engine shop look at it. Thanks again for all your help. You're all what make Mooneyspace GREAT!

 

-Kyle

[carusoam]

Thanks for sharing your findings, Kyle.

That is pretty interesting.

Best regards,

-a-