Exhaust Valve About Done Come from Together

Ted

Ted

The pilot formerly known as Twin Engine Ted
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iFlyNothing
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The #4 cylinder on the 414 burned its exhaust valve.

Indications were significantly higher EGT on the #4 cylinder on the engine monitor, coupled with the EGT varying some during normal cruise flight.

On the last leg of the flight on the hot start it seemed like one cylinder wasn't providing any resistance to the starter. Engine passed mag check and made power, though, so we decided to get home. It was cold and we were lightweight, so good performance.

Get it into the shop the next morning: 0/80 compression, with it all leaking past the valve.

Cause? Well it's a Continental that's got >1,000 hours on it.

Cylinder is off, new one is in shop, and getting put on. Will be done in time for my next rescue flight this weekend. Only 16 hours this time instead of 35.
 
nice....:D

good to see misery loves company.....My top OH is on the mend and we are in the assembly process. Maybe by Christmas the Bo will be running.
 
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I came across this pdf a couple years ago. That picture reminded me of it:
 

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Yup. Burnt valve. Another thank you to CMI.
 
Yep 2 weeks ago, owner says it started skipping until hot then it runs fine.. #4 cylinder (cold) no compression, I couldn't find compression stroke by spinning the prop. Put my differential compression tester on the cylinder and added 80psi, still could not tell where compression stroke was. you could hear the air whistling thru the exhaust.
I stopped the annual, told the owner to remove the #4 & #2 and bring them to me. We will see what can be done to them to unstick the valve.
It's a high timed engine and not really worth 6 new cylinders the other 4 are mid 70s.
 
I was expecting to see a "burned exhaust valve". I've seen them, and they were much worse than that, like, part of the valve missing copletely.
 
GRG55 said:
"THE #4 cylinder on the 414..." o_O
Doesn't it have two of those? ;)
Click to expand...

Fine. Left engine. ;)

GlennAB1 said:
I was expecting to see a "burned exhaust valve". I've seen them, and they were much worse than that, like, part of the valve missing copletely.
Click to expand...

It's considered poor form to wait until a piece of the valve breaks off to fix the issue.

This is a burned exhaust valve. Fortunately it was caught before it became a broken exhaust valve.
 
Wat exactly are we seeing in the picture? I see the circular discolorations, but what is it exactly?
 
Salty said:
Wat exactly are we seeing in the picture? I see the circular discolorations, but what is it exactly?
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check out this chart....AOPA put together good to bad views.
c4a66675ca4d6287df93f72529c2df1c.png
 
So he pattern is showing that the valve isn't seating properly?
 
Salty said:
So he pattern is showing that the valve isn't seating properly?
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correct. The leaks cause the valve to warp and not seat and seal....and over heat The valve needs 360 degree contact to get good heat transfer to conduct heat out thru the seat and head. The majority of the time the valve is closed and seated. During this phase it needs good contact with the seat to conduct heat away.
 
This is probably as good an outcome for a burned valve as you can have and certainly is a great advertisement for engine monitors. This valve was failing and was caught before it caused any real issue, which from my understanding can range from a rough running engine to a catastrophic engine failure should the valve end up stuck and meet the piston.
 
PaulS said:
This is probably as good an outcome for a burned valve as you can have and certainly is a great advertisement for engine monitors. This valve was failing and was caught before it caused any real issue, which from my understanding can range from a rough running engine to a catastrophic engine failure should the valve end up stuck and meet the piston.
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The bigger concern is that the valve head snaps off and starts rattling around. That happened to a friend of mine on his Columbia - basically needed a new engine.

Yes, it's about as good of an outcome as one can have and a good advertisement for engine monitors. On these bigger, more powerful engines, it's an important piece of equipment.
 
Ted any way to know if the stem is loose in the guide, any wobble on that one?
 
Let'sgoflying! said:
Ted any way to know if the stem is loose in the guide, any wobble on that one?
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I haven't looked. Honestly I'm more focused on getting the plane back in the air for this weekend's trip to save the next 40.
 
PaulS said:
This is probably as good an outcome for a burned valve as you can have and certainly is a great advertisement for engine monitors. This valve was failing and was caught before it caused any real issue, which from my understanding can range from a rough running engine to a catastrophic engine failure should the valve end up stuck and meet the piston.
Click to expand...

I would add that you also need a pilot with (a) good habits to note the change, (b) knowledge to know what it might mean, and (c) super discipline to pull the plane out of service (certain assured time and $$ impacts to avoid uncertain unassured greater time and $$ impacts). Trusting that the monitor was to be believed and knowing you're losing time and money may be better than the just-possible greater time and $$ impacts of catastrophic engine failure and forced landing. I only hope to be that good when I get a monitor...
 
Checkout_my_Six said:
correct. The leaks cause the valve to warp and not seat and seal....and over heat The valve needs 360 degree contact to get good heat transfer to conduct heat out thru the seat and head. The majority of the time the valve is closed and seated. During this phase it needs good contact with the seat to conduct heat away.
Click to expand...

Not trying to beat a dead horse here but I really want to understand this.

The color poster on the exhaust valves all indicate some kind of uneven wear on the valve itself.

In the ops case I see no indication of uneven wear on the valve itself - or I'm too blind to comprehend it? The "wear" or markings on the ops valve looks quite even to me. Closer to the "pizza" example on the color poster, which according to the color poster is OK. Or am I wrong?

What is noticeable is the uneven build-up around the valve on the cylinder itself. Is that the actual indication of the bad valve in this case?

TIA
Gary
 
uniformity is what you're looking for....concentric rings...like a pizza. Ted's valve face is not "uniform". There are the beginnings of green areas in two regions. Those areas will eventually break free and beat the cylinder and engine....and my possibly float back thru the intake to another cylinder.
Lndwarrior said:
Not trying to beat a dead horse here but I really want to understand this.

The color poster on the exhaust valves all indicate some kind of uneven wear on the valve itself.

In the ops case I see no indication of uneven wear on the valve itself - or I'm too blind to comprehend it? The "wear" or markings on the ops valve looks quite even to me. Or am I wrong?

What is noticeable is the uneven build-up around the valve on the cylinder itself. Is that the actual indication of the bad valve in this case?

TIA
Gary
Click to expand...
 
Lndwarrior said:
Not trying to beat a dead horse here but I really want to understand this.

The color poster on the exhaust valves all indicate some kind of uneven wear on the valve itself.

In the ops case I see no indication of uneven wear on the valve itself - or I'm too blind to comprehend it? The "wear" or markings on the ops valve looks quite even to me. Closer to the "pizza" example on the color poster, which according to the color poster is OK. Or am I wrong?

What is noticeable is the uneven build-up around the valve on the cylinder itself. Is that the actual indication of the bad valve in this case?

TIA
Gary
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There isn't any "wear", just a color change in the metal itself. Look at the upper and lower edges of the left-side valve. You'll see orange radiating from the 12 and 6 o'clock positions. Compare that to the color of the valve on the right.

Look at image #2 on the poster.
 
the orange or red is fine....it's the green on the 3 and 9 o'clock positions that's the problem.
 
Checkout_my_Six said:
the orange or red is fine....it's the green on the 3 and 9 o'clock positions that's the problem.
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Your monitor is better than mine. I see the red/orange, but I need to look at it on something other than this crappy monitor I have.

edit:

OK - yeah, it looks like the 3 and 9 correspond more closely to the #5 picture.
 
Checkout_my_Six said:
uniformity is what you're looking for....concentric rings...like a pizza. Ted's valve face is not "uniform". There are the beginnings of green areas in two regions. Those areas will eventually break free and beat the cylinder and engine....and my possibly float back thru the intake to another cylinder.
Click to expand...
Ok, I was looking at the wrong valve then? It's the "clean" one in the photo?
 
Lndwarrior said:
Ok, I was looking at the wrong valve then? It's the "clean" one in the photo?
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the smaller valve on the left is the exhaust valve....and the coloration at 3 and 9 o'clock positions are indicating an issue.

Left alone....the 3 and 9 o'clock positions would eventualy turn bright green before cracking free.
 
Where it can lead...

31181368330_1f220e3071_z.jpg


The associated piston (which I still keep as a ashtray for our nicotene-addicted friends):

31382727126_a53c8592e9_z.jpg


A renter had the valve fail in our Citabria and made an emergency landing at Homestead Air Force Base.

Made an award for him:

31406787212_794a07ba22_z.jpg


Never got it to him. Can't find him now.

Anyone know him?
 
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Engine monitors are a damn good tool to have and really help spot this stuff in advance.

Just a tip for those of you that don't know - generally if you have a compression issue that needs fixed - you can easily feel it by pulling the prop through by hand and counting the compression strokes. I've never seen a cylinder that needed fixing that you couldn't easily feel. It's also worth paying attention to things when you're cranking during start. You'll notice it there too - like Ted did.

I make a habit of pulling an engine through by hand from time to time. It's a hell of a lot faster than a compression check and tells me what I need to know.
 
jesse said:
Engine monitors are a damn good tool to have and really help spot this stuff in advance.
Click to expand...

Was leaving on a trip, on climb I noticed EGT on one cylinder was 4-500 above the others. Pulled power back, stayed full rich, opened cowl flaps, and returned home. Mechanic found a partially plugged fuel injector. JPI good!
 
Cherokee ate a valve once. Broke up and went out the exhaust pipe and I glided into CVG. Still had enough power to taxi but nothing else.

Long before engine monitors:rolleyes:

Cheers
 
jesse said:
Engine monitors are a damn good tool to have and really help spot this stuff in advance.

Just a tip for those of you that don't know - generally if you have a compression issue that needs fixed - you can easily feel it by pulling the prop through by hand and counting the compression strokes. I've never seen a cylinder that needed fixing that you couldn't easily feel. It's also worth paying attention to things when you're cranking during start. You'll notice it there too - like Ted did.

I make a habit of pulling an engine through by hand from time to time. It's a hell of a lot faster than a compression check and tells me what I need to know.
Click to expand...

I recently finished building my first airplane and, after I did a compression check, I was concerned about one of my cylinders. I asked a local A&P to take a look at it for me. I was thinking he was going to come over with a bunch of tools and start pulling stuff apart to "analyze" the problem.

Instead he walks into my hangar, checks the switches are off, grabs the prop and starts turning it.

"Yep, you have a problem. You may need to reset the valve lash. Call me if you need help," and walks out.

Honestly, I was thinking, "WTF?". I seriously was not sure if he was joking or not, but was too embarrassed to ask. And I did not want to impugn his judgement.

A few minutes later a very knowledgeable local pilot comes strolling in and asks, "what did he say?". So I told him the story and he said, "Yep, a good mechanic can tell by rotating the prop. You want some help re-setting the valve lash?"

"Yes please."

And resetting the VALVE lash fixed the problem (O-235-C1).

Afterwards I dropped an envelope with some cash in it to the mechanics hangar. $40 for 5 minutes of his time was totally worth it.
 
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are we using 'backlash' to mean tappet clearance now?
I suppose its right but I've always thought of it as being a gear tooth thing.
 
FastEddieB said:
Where it can lead...

31181368330_1f220e3071_z.jpg


The associated piston (which I still keep as a ashtray for our nicotene-addicted friends):

31382727126_a53c8592e9_z.jpg


A renter had the valve fail in our Citabria and made an emergency landing at Homestead Air Force Base.

Made an award for him:

31406787212_794a07ba22_z.jpg


Never got it to him. Can't find him now.

Anyone know him?
Click to expand...

Sophie, isn't that a female name? If I were a male w/ that name I might be hard to find also. ;):)
 
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