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Extra 400 upgrade project - call for advice

Thank you Michael. You are right: the cylinders have only been inspected (using a dye). At the moment, one of them is with Dachsel, a renowned German overhaul shop for an analysis of the cause of the failure. We’ll see what they have to say about the work done in Canada.

The issue I have with the pre ignition hypothesis is that there is no visible anomaly on the EGT curves. I could post them here if you want me to.
Also: pre-ignition should impact (literally) performance and smoothness. I was flying myself during the last cylinder death event and I noticed no roughness and no loss of power. Subsequent borescoping showed no damage to the piston’s face either.

Latest idea: The plugs may be OK, and the issue would reside in the water cooling (air bubble).
This fits well with the absence of symptoms before the crack that eventually happened and let coolant into the cylinder.
The subsequent CHT rise is easily explained by the coolant washing away the oil film from the barrel and causing a massive increase in friction that became visible despite the “smoke screen” from water cooling.

Problem with this idea : my shop in Germany completely dismisses this possibility on the basis that they always follow the Continental procedure for purging any air out and never had such a problem with several other engines they maintain.

I just don’t understand why 3 cylinders (and counting) would develop a crack without showing any of the usual symptoms of abnormal combustion.
Let’s see what Dachsel find out…

Please keep input coming. Much appreciated.

LSGG, LFEY, Switzerland

Flyingfish wrote:

The issue I have with the pre ignition hypothesis is that there is no visible anomaly on the EGT curves. I could post them here if you want me to.
Also: pre-ignition should impact (literally) performance and smoothness. I was flying myself during the last cylinder death event and I noticed no roughness and no loss of power. Subsequent borescoping showed no damage to the piston’s face either.

Agreed – if you were experiencing pre-ignition, it would show up on the EGT trace and you would experience vibration and pinging noise, but if you don’t have alot of experience wit the acft you might not notice it.

Latest idea: The plugs may be OK, and the issue would reside in the water cooling (air bubble).
This fits well with the absence of symptoms before the crack that eventually happened and let coolant into the cylinder.
The subsequent CHT rise is easily explained by the coolant washing away the oil film from the barrel and causing a massive increase in friction that became visible despite the “smoke screen” from water cooling.

Problem with this idea : my shop in Germany completely dismisses this possibility on the basis that they always follow the Continental procedure for purging any air out and never had such a problem with several other engines they maintain.

I have a hard time with the “coolant washing oil from barrel” scenario – IMHO , highly unlikely.

I just don’t understand why 3 cylinders (and counting) would develop a crack without showing any of the usual symptoms of abnormal combustion.

What is the history of these cylinders ?

FAA A&P/IA
LFPN

Michael:

All 6 cylinders were “mine” and have been refurbished in Canada by Alberta Aero Engine. the first two that failed where CMI-refurbished cylinders with the Nikasil treatment. I have no access to their paperwork.
The third one was a spare that they had recovered from another engine and supplied.
It had about 600 hours from new and had recently been overhauled (25 hours since OH).

All 3 failed cylinders had in common:
- new valve guides
- new exhaust valves
- valves recut to fit
- cylinders NDT checked before honing
- new piston assemblies
- everything balanced

Back to pre ignition: I think we can rule this out: while I do not know this plane well, I am very interested in engine management and have an “ear”. This engine was running fine and making tons of power. But what caused overheating???

I have in the meantime received the results of resistance tests at low voltage of my Champion fine wire spark plugs. 10 out of 12 were open circuit, one was several megohm and one was 8 Kohm. I am in touch with Champion’s support to figure out whether they do have the “new manufacturing process” for this specific plug. It seems not…
Champion’s line is “if they make sparks under high voltage and pressure, all is well”…

LSGG, LFEY, Switzerland

Flyingfish wrote:

All 6 cylinders were “mine” and have been refurbished in Canada by Alberta Aero Engine. the first two that failed where CMI-refurbished cylinders with the Nikasil treatment. I have no access to their paperwork.
The third one was a spare that they had recovered from another engine and supplied.
It had about 600 hours from new and had recently been overhauled (25 hours since OH).

I’m confused – you say that all 6 were yours, but 3 came from other sources ?

Are new cylinders no longer available ?

FAA A&P/IA
LFPN

Michael, here is the story:
Originally, Alberta Aero repaired “my” cylinders, 6 of them.
As they started failing they sourced used cylinders and repaired and sent them. they have sent me 2 units so far and are preparing a third one
New cylinders have a long lead time… only option in stock is ECI and I don’t want them.

LSGG, LFEY, Switzerland

Flyingfish wrote:

New cylinders have a long lead time…

Yes, well, but looking at your saga, it might not be the worst idea to source some in the near future. If you don´t want ECI, then I suppose the originals should be available as well, if with longer lead times. But if things continue as they do, it might be the safer option to go for a complete set of new ones eventually.

LSZH(work) LSZF (GA base), Switzerland

Mooney Driver you are right for a medium term strategy.
But as long as the CAUSE of the failures is not determined, we cannot simply assume that the present cylinders are defective.
It is quite possible that an external cause is there. If this is true, it would destroy any cylinder – even new ones…

My coolant pump has been removed for inspection. For a reason I cannot explain (I thought we had overhauled or replaced ALL of the engine peripherals) I have been informed today that this pump had been left as is. I am very confused and upset…

LSGG, LFEY, Switzerland

Do you have an engine coolant temperature indicator? What did it show? Was the temperature way below what you expected to see?

LFPT, LFPN

For a reason I cannot explain (I thought we had overhauled or replaced ALL of the engine peripherals) I have been informed today that this pump had been left as is. I am very confused and upset…

Ugh! Yes I’d be upset too… now what else may not have been done as required? You are very right, this needs to be gotten to the bottom of. All of it. The way this looks, there could be more to this engine than meets the eye.

LSZH(work) LSZF (GA base), Switzerland

@Aviathor:
“Do you have an engine coolant temperature indicator? What did it show? Was the temperature way below what you expected to see?”

Yes we do, except it is the old steam gauge because JPI did not deliver the coolant temp sensor after 6 months of ordering. If you want terrible service in Europe, go JPI.

The coolant was getting hotter and hotter (yellow arc) but I did not let it get to redline and landed before.

The coolant pump is now with Dachsel for a check. I hope it is overhaulable because I was told you cat’t get them new for the TSIOL 550C…

LSGG, LFEY, Switzerland
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