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  #1  
Old 03-25-2016, 09:41 AM
chipf chipf is offline
 
Join Date: Feb 2008
Location: Austin, TX
Posts: 179
Default Tale of a sticky valve

I recently completed all of the tasks on checklist for the annual.
For the oil change, there was only one tiny piece of metal in the filter, and the finger filter was entirely clean. All previous oil analysis has been normal, and I've only seen metal in the filter the first couple of oil changes.

I was ready to print out the logbook stickers, sign them, and go flying. But first I had to check compression and put spark plugs back in.
Numbers were 74 20 79 79. Dang.

I'd been having some morning sickness symptoms, but they hadn't happened since November, about 40 hours of flying. But suddenly they were back. EGT temps showed that #2 was dropping out. Sure enough, the #2 was hissing at the exhaust on the compression check.

OK, time to call the local (88R) mechanic and ream a valve guide.

I arranged to meet him and had everything ready to go. He pulls the spring
and has to hammer the valve through into the cylinder. It is really stuck. But we get it through and he uses a borescope to look at the valve guide. He doesn't like what he sees, lots of smearing, that's the way I would describe it.
He says he doesn't think that reaming and returning to service is a great idea. So off comes #2.



We look inside:


The cylinder looks ok, but the valve is showing signs of cracking at the center. His assessment is that the yellow is indications of sodium leaking out.

With the cylinder out, we are able to see some of the cam lobes. Really bad news, significant spalling on #1 exhaust. Oddly, #2 looks fine.
So now a bit of morning sickness has turned into an engine teardown.
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RV-9A N207LT
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Last edited by chipf : 03-25-2016 at 09:44 AM.
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  #2  
Old 03-25-2016, 09:51 AM
chipf chipf is offline
 
Join Date: Feb 2008
Location: Austin, TX
Posts: 179
Default Part 2 - The really bad news

So I start stripping the FWF work that took so long to do 5 years ago. It comes off a lot faster.




We move the engine to his hangar and he supervises as I start disassembling an aircraft engine.





The parts to go to various shops in Tulsa. Here's a couple of glamour shots of my crankshaft:


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Last edited by chipf : 03-25-2016 at 09:51 AM. Reason: adjust spacing
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  #3  
Old 03-25-2016, 10:47 AM
chipf chipf is offline
 
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Location: Austin, TX
Posts: 179
Default

BTW, I wrote up this post hoping to solicit comments from the experts who know how to interpret the crankshaft images. To me they're just pretty pictures.
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cfrv9aproject.blogspot
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  #4  
Old 03-25-2016, 11:42 AM
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Planecrazy232 Planecrazy232 is offline
 
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Location: Cape Coral, FL
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Default

Any photos of the cam?
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  #5  
Old 03-25-2016, 11:55 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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Default

Quote:
Originally Posted by chipf View Post
BTW, I wrote up this post hoping to solicit comments from the experts who know how to interpret the crankshaft images. To me they're just pretty pictures.
You should rely on those experts in interpretation of magnetic particle inspection results on aircraft engines.

Thanks for these posts, was your valve train using slipper followers or roller followers? How many hours since new and OH?

Pictures of the cam/followers would be interesting.
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  #6  
Old 03-25-2016, 03:25 PM
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JohnInReno JohnInReno is offline
 
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Location: Prescott Valley/Chandler AZ
Posts: 352
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Quote:
Originally Posted by BillL View Post

Thanks for these posts, was your valve train using slipper followers or roller followers
I believe roller followers all have bolts in the top of the case above where the followers would be. None are apparent in photo #1.
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  #7  
Old 03-25-2016, 04:19 PM
chipf chipf is offline
 
Join Date: Feb 2008
Location: Austin, TX
Posts: 179
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The engine has 498 hours SMOH. I don't have logs from before that.

It is an older engine, does not have roller tappets. I don't have pictures of the cam right now. I took pictures with my new VA-400, but I must have done something wrong, since they weren't on the computer when I got home.

The story is still unfolding, I should know more about the cam and case parts next week.
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  #8  
Old 03-28-2016, 11:08 AM
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goatflieg goatflieg is offline
 
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For what it's worth... when it comes to aircraft engines, morning sickness is much better to have than airsickness.
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  #9  
Old 03-28-2016, 11:11 AM
rhill rhill is offline
 
Join Date: Feb 2006
Location: Valley Forge, Pa
Posts: 663
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Well..... It's a early wide deck with fixed through studs,cam wear and cam failure can happen at about 50/50 mix if all things being equal. Send everything out for inspection&tagging. I suspect these exhaust valves were reused at overhaul (big no no in my book). New exhaust valves at a minimum a cam &lifter kit if you can swing it. new limits not service limits on everything else.The goal is to build a 2000hr engine.Saving 5K on a used engine to only get 1/4 of its life is a bad financial risk.IMHO
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