Sticky valve_Lycoming IO-360-A3B6D

[Marauder]

Thanks for the update Brett. Any idea why it happened (i.e. where the carbon came from)?

[bnicolette]

How many hrs since your teardown?

 

There is 700 hours on the engine

[bnicolette]

Thanks for the update Brett. Any idea why it happened (i.e. where the carbon came from)?

 

Must be common enough Chris to warrant Lycoming having the Mandatory Service Bulletin.  I had not heard of it before and the scary thing is either has my shop/mechanic.  It really is an easy fix and am glad that we tended to it now.  I wasn't there to see how difficult it was to work the valve back up into the guide but it's like working in the blind and I bet that will be the hardest part.

[mcpilot]

This is very common for all angle valved Lycoming engines...  The Cessna Cardinal RG also has the same engine.

 

THe carbon buildup is from running overly rich and high CHT.  Lead fouling also may add to the mix...

 

Adding TCP from Alcor to the fuel and using Gamijectors and running LOP goes a long way to helping prevent this.

[PTK]

Must be common enough Chris to warrant Lycoming having the Mandatory Service Bulletin.  I had not heard of it before and the scary thing is either has my shop/mechanic.  It really is an easy fix and am glad that we tended to it now.  I wasn't there to see how difficult it was to work the valve back up into the guide but it's like working in the blind and I bet that will be the hardest part.

Brett, this is what dental floss is for! Tie it and drop it in the combustion chamber. Then fish it back out.

You do use floss don't you!

[bnicolette]

Brett, this is what dental floss is for! 

 

That's a great idea Peter!  He's got the end of the valve sticking up through the spark plug hole.  Maybe I better take him in some tomorrow morning and also a couple instruments to fish the line through the valve guide.  

[tony]

I heard that Lycoming increased the red line for oil pressure for new engines installations, along with a higher nominal pressure, by 10 pounds.  The rumor (of course Lycoming would never admit to this) is that with a higher pressure, you would get more oil down the guide.  Just folklore I guess.....

 

So it has me wondering if that non FAA approved fuel additive made by marvel mystery oil would help?

 

 

On another note:  Has anyone bought this yet?  I was thinking it might be good to have at the hanger ......

http://www.aircraftspruce.com/catalog/topages/valvewobble.php?clickkey=34395

[wishboneash]

I lost my engine (or rather had very rough running engine) on take off last weekend and aborted the takeoff on time. It could have been an off airport landing if I had taken to the air and was lucky it happened on the runway. The options for an off airport landing wouldn't have been good at that location/runway. Found out that cyl 1 intake valve unseated as seen on the borescope. I will be taking off the cylinder this weekend. I am not sure if it could be due to a stuck valve. My compressions were all above 76 until this incident, CHTs from 315 to 345 (cyl #4 being the hottest) and oil temp between 188 and 193. I lean aggressively on the ground and engine was running smoothly until this happened. The same cylinder lost compression last year. 

[romair]

Hey Wishboneash

do you mind taking pictures of the valve and the cylinder and post them once able?

Stefan

'89 M20J

[aaronk25]

I lost my engine (or rather had very rough running engine) on take off last weekend and aborted the takeoff on time. It could have been an off airport landing if I had taken to the air and was lucky it happened on the runway. The options for an off airport landing wouldn't have been good at that location/runway. Found out that cyl 1 intake valve unseated as seen on the borescope. I will be taking off the cylinder this weekend. I am not sure if it could be due to a stuck valve. My compressions were all above 76 until this incident, CHTs from 315 to 345 (cyl #4 being the hottest) and oil temp between 188 and 193. I lean aggressively on the ground and engine was running smoothly until this happened. The same cylinder lost compression last year.

You running cam guard?

[jetdriven]

I lost my engine (or rather had very rough running engine) on take off last weekend and aborted the takeoff on time. It could have been an off airport landing if I had taken to the air and was lucky it happened on the runway. The options for an off airport landing wouldn't have been good at that location/runway. Found out that cyl 1 intake valve unseated as seen on the borescope. I will be taking off the cylinder this weekend. I am not sure if it could be due to a stuck valve. My compressions were all above 76 until this incident, CHTs from 315 to 345 (cyl #4 being the hottest) and oil temp between 188 and 193. I lean aggressively on the ground and engine was running smoothly until this happened. The same cylinder lost compression last year. 

Isnt that a fresh overhaul, Ash?

[wishboneash]

Isnt that a fresh overhaul, Ash?

 

It was overhauled last year - yes. Last time it was partial loss of compression and the leak was not easy to find with the borescope. To answer the other questions, I will take pics for sure and no, I don't use Camguard. 

[bnicolette]

Picture of today's engine run after reaming the #1 valve guide.  Back to normal.

 

[fantom]

I don't use Camguard.

Then it must be that LOP thing

[DaV8or]

Since we have this stuck valve thread, I might as well add my very recent stuck valve story.

 

I took my plane up to LASAR for the annual and it ran fine all the way there. I have never had the issue of "morning sickness", or any roughness on idle except after shut down and then a hot restart. I always just chalked that one up to just "a Lycoming thing". Anyhow, all was well until I pulled the power back in the traffic pattern at Lampson. It for the first time ever ran a little rough. Oh well, land the plane, go straight to annual.

 

First thing they do on the annual when you pull up is the compression test while the engine is still hot. Well, all the cylinders came up perfect except #1. On #1 they got zero compression. That was odd. It ran a little rough in the pattern, but not one dead cylinder rough?!!

 

They pulled the prop through several times and tried it again and again, several times with the same result. Zero compression. You could hear the air blowing out the exhaust system, so we knew it was the exhaust valve. They decided to try "staking" the valve. For those that don't know, that is aircraft mechanic speak for, beat on it with a hammer.

 

The first several times they tried, nothing, still zero. Not giving up, about the 4th time we got it up to about 25 lbs compression and this gave us hope. One more whack and Voila! Perfect compression on #1. Michael, the IA mechanic there had the theory that just "a piece of crud" got stuck in the guide and it was now free.

 

I still wanted it checked out, so after I left (I was not able to stay for the whole annual this time) they did the rope trick and checked the fit of the valve in the guide. They said it felt perfect, so no further work was done on it. They ran her up and did another compression check and it came out perfect on all cylinders.

 

Happy ending, but I still worry about this "piece of crud" and this brings me to my own theory as to where this crud came from. Both my #1 and #2 cylinders run really cold all the time. I have to really flog the engine to get them to go over 300 CHT. They typically cruise about 280 something to 290 something. I run LOP most of the time, but even ROP only raises the CHT about 10 degrees as I keep it at 65-70% power.

 

I have read that ideally, you need to keep your cylinders over 320 so that the additive that is in 100LL to scavenge the lead can do it's job. I have read that cold cylinders lead to lead deposits. This is exactly what I believe I saw when I had the spark plugs out on #2 last year when I had trouble with my flow divider. It looks like a flaky crust on the top of the piston and presumably, it may be on the top of the cylinder head as well.

 

Maybe this is where the myth that LOP causes burned valves comes from, because a sticking valve will quickly become a burned valve if it doesn't free itself up. Maybe in some applications like mine, LOP lowers the cylinder head temps so much that lead build up occurs and on occasion, sticking valves from "a piece of crud" breaking loose and getting stuck in the guide.

 

I have heard of a fuel additive you can get to help scavenge the lead from your cylinders and I'm willing to try it, but what I can't find out from anyone is, does it help remove existing deposits, or does it only prevent future deposits?

 

Also, Lycoming many years ago released a SI 1418 on how to clean the inside of the combustion chamber with walnut shell medium without removing the cylinder. I asked on the internet about this procedure and few people were familiar with and had to look it up. Most all were very skeptical as to it's usefulness. Anybody here know anything about it? I'm going to ask LASAR about it today.

[wishboneash]

Then it must be that LOP thing

 

Yeah, I run LOP all the time. I am going to try Camguard going forward.  

[carusoam]

Expect the walnut shell to be similar to sand blasting with a soft medium....

I have no experience with it though...

Best regards,

-a-

[Marauder]

Picture of today's engine run after reaming the #1 valve guide. Back to normal.

Well Brett, you just absolutely, 100%, without a doubt, confirmed my decision to buy an engine analyzer capable of recording these events. At least that is the story I am going to use with the wife to justify the expenditure

[KSMooniac]

All of us should have engine analyzers IMO.  They offer so much capability relative to the cost that it should be a no-brainer.  In fact, if you disagree with that assessment, I would go so far as to say that you likely don't understand how to actually *use* one!  There are used EDM-700s turning over on the secondary market now for very modest money, and an enterprising owner can install the probes under supervision to keep the costs down as it is simple work, just tedious.

 

My own personal story about the discrete benefit of having one revolves around a faulty Champion plug a couple years ago... I stopped for cheap fuel on my way home one afternoon, After restarting, the EDM-700 showed a high EGT on one cylinder, and doing a mag check confirmed a dead plug.  Luckily there was a mechanic still working, and he loaned me a screwdriver and wrenches to remove the cowling and plug, and then he tested the plug to confirm it's condition.  He then sold me a plug that he fortunately had on the shelf, and I was on my way with only a 30 minute delay vs. who-knows-how long it would've taken to determine what was causing the roughness on a mag check prior to takeoff.  (spare plugs and tools went into my baggage kit after this episode)

[carusoam]

So many available from so many different sources, and new vs used....

Get one if you don't have one. Even the entry level Mooney deserves one.

Best regards,

-a-

[Jsavage3]

Picture of today's engine run after reaming the #1 valve guide.  Back to normal.

 

GREAT news!!!  Thanks for sharing!

[Jsavage3]

I have heard of a fuel additive you can get to help scavenge the lead from your cylinders and I'm willing to try it, but what I can't find out from anyone is, does it help remove existing deposits, or does it only prevent future deposits?

 

 

Marvel Mystery Oil perhaps?  I personally don't use it (yet), but I'm certainly paying attention to its pros-n-cons.

[bnicolette]

Marvel Mystery Oil perhaps?  I personally don't use it (yet), but I'm certainly paying attention to its pros-n-cons.

 

Alcor TCP is probably what they're referring to.

[jetdriven]

Marvel Mystery Oil perhaps?  I personally don't use it (yet), but I'm certainly paying attention to its pros-n-cons.

i think the problem with MMO is that it can cover up a sticky valve only for it to stick in flight and cause an accident later.  Its great for flushing carbon out of the rings and elsewhere, though.

 

If I had a suspected sticking valve I would do as the OP did, remove it and ream the guide.

[N9201A]

Have a 201 with a mid-time engine, engine analyzer, PowerFlo, only run ROP (mine doesn't seem to like LOP, no GAMI-jectors), lean aggressively on ground.  I had one cylinder (no. 2) consistently fouling on runup, would always clear up before take-off.  Switching to fine-wire plugs in that cylinder didn't help, still recurred.  

 

Then on a trip no. 2 EGT began to climb beyond normal disparity, engine running rough.  Smoothed out just as I began to divert so I continued and mechanics at destination could not duplicate, home IA opined via phone some deposits had fouled and then come loose.  Upon returning to base, checked valves and discovered one sticking exhaust valve.  

 

Bottom line?  The "fouled plug" ... wasn't.  Next time I get out of ordinary readings when I know I've been leaning aggressively I will look at this FIRST.