Stuck valves

[N170BP]

So, after 653+ hours on the trusty ole', C-145, I finally
had a stuck valve today. Blasted off, got about 1/2 mile
away from the airport (1500 or so AGL) and "poof", the thing
started running like s....

I lean on the ground like a you-know-what, and I also lean in the
air (as much as I dare do), but bottom line, I'm surprised I didn't
have an issue like this earlier what with my running 100LL
through this thing exclusively....

The good news, is after doing the rope-trick (moving the #5
exhaust valve back and forth a billion times while squirting Kroil
in there), it came un-stuck pretty much all by itself. A neighbor
with a '53 C-195 stopped by and showed me the trick of clamping
a piece of fuel hose (right diameter) around the valve-stem when
you get it loose, and spinning it with a drill motor (kinda "lapping"
it in-place). Anyway, it's all back together now and running well,
but I can't claim the "I just lean the !@#$ out of it, and it's fine" story
anymore....

I'll either have to run car gas, or add TCP.

My one thought is if the #5 exhaust valve "sticked", how far
off are the rest of them from sticking? I'm tempted to do the
Kroil / clamped fuel-line/tube thing on all the exhuast valves
(lap them in place) to alleviate further concerns.

Thoughts?

[kimble]

Bela,

You will probably receive a lot of advice on this subject. In my humble opinion, the rope trick is a tempory fix at the best. If you had kicked the valve back into the cylinder and reamed the guide, it would have been better. Do not try this unless you are patient and a good fisherman. The best solution is pull the cylinder and do it right.

However, prevention is the even better solution. I have "been told" that four ounces of Marvel Mystery oil to ten gallons of 100LL helps prevent the valve sticking problem and it's a lot cheaper than TCP. I have not personally tried this solution, but the recommendation came from a trusted source.
I ran a Pawnee on a 50/50% auto/100LL fuel mixture for several years and had good luck. I also ran a straight auto fuel and had mostly good luck with the auto fuel. However, note that auto fuel has a short storage life, it gums and can deterorate certain parts of the fuel system.

Listen to all the good advice and do what you think best. It's your posterior setting in the pilot's seat.

Ralph

[Metal Master]

Hello! Bela,

I just did the rope trick on a customer’s airplane a few weeks ago. It was a 180 HP Lyc. But the issue is the same to my way of thinking. He was convinced that the sticking valve was the #1 cylinder. Something to do with the fact that he had experience the issue with that cylinder before. He only wanted to do the #1 cylinder. We dropped the exhaust and dropped the valve into the cylinder so that we could ream the crud out of the guide. (With the appropriate sized ream). I talked him into doing all four cylinders. The #1 was marginally tight. The #2 & #3 were as loose as when originally fitted. The #4 had to be driven out with a brass drift. I have often thought that lapping the valves as you described might work to free the valves but would only serve to get the a cylinder back in service for a while only to bring the issue back sooner than later because all of the carbon and solidified C*** in the guide doesn’t get completely removed.
It has been my experience that a compression test does not always identify the sticking valve because the rotation of the engine is so slow and the spring pressures so high that the valve closes any way. Occasionally the valve will stick open even during a compression test because it is so tight. Sometimes all of the exhaust valves stick and sometimes only one of them sticks. But the one comment I get from owner operators after doing the ream job on a complete set of cylinders on an engine that seems to have the problem is this. “(This engine has not ran this well in a long time!)”.

So my suggestion is. If you are experiencing the issue on one cylinder do a complete ream job on all cylinders. You may or may not find the issue on all of the cylinders but you will be less likely to have the issue while you are on your way to a vacation fly in or trip.

Regards,

Jim

[GAHorn]

I don't care for the idea of "spinning" a valve in a dirty guide. If indeed lead, crud, carbon, or whatever has gotten in there and "stuck" the valve, then that stuff will still likely be in there and might score/scratch the guide and valve stem. This would contribute to further sticking, I believe.
I believe the best fix is to drop the valve (remove the cylinder if necessary) and ream the valve guide with the correct size reamer, clean the valve stem, and then reassemble.
While I am an avgas proponent for what I believe are all the right reasons, it's likely the lead in avgas that contributes to the valve sticking problem. TCP is a weapon against the lead, (and according to MMO proponents, so is MMO. My view of MMO is that it's a solvent and does not belong in an operating engine's oil sump, and if kerosene/jet-fuel/diesel is a fuel contaminate, ...then it doesn't belong in the fuel either.) There's nothing better than a well assembled engine that meets it's design dimensions and that's well cared for with the right lubricants and fuels....and when if/when it malfunctions....it should be repaired in accordance with well accepted and approved practices.
I know lots of good and caring owners tho', who swear by MMO in the fuel and oil. I suspect diesel fuel or light machine oil would be just as good.

[Bruce Fenstermacher]

Bella

I've used MMO on and off. Never had a stuck valve while using it but have with out it. If it is a fuel contaminant it hasn't effected my engines in anyway that I can tell. But we've had this discussion before.

At for the stuck valves I've had about 5 between my A-65 and C-145. I would only free a valve to get home as you describe. I would and have removed the valves and cleaned the valve stem and cleaned/ream the valve guide. All of this can be done rather easily through just the open spark plug holes. I've done one on my Cub in 25 minutes. I've done the left and then the right bank of 3 cylinders on my C-145 in an afternoon.

Might take you 2 hours to do the first but the last cylinder will take a quarter of the time.

[zero.one.victor]

Bela: car gas- better as well as cheaper. Nuff said.


Eric

PS don't forget the hokey-pokey

PPS I'm planning to fly down to Elma for lunch tomorrow(memorial day), around noonish. Come on out.

[Harold Holiman]

I used MMO in the gas of my former 170, on recommendation of my old mechanic who had been flying since the 1920's, for seven years and never had a stuck valve. I did not use it in the oil. I currently use it in the gas in my current 180 though I don't use it with every tank. I run both 100 ll and auto fuel depending on which is available. In the winter when I am not flying much I use only 100 ll as I don't believe auto fuel has a good shelf life sitting. George I know you and the FAA call MMO snake oil but I believe it works.

Harold
N92CP

[N1478D]

I've had stuck valves running mogas with and without MMO, and running avgas with and without MMO. IMHO, if a valve is going to sick, it's going to stick no matter what juice you have in there. Ream your guides, or, pull the cylinder and do even more - like really check the valve for signs of a ridge that could be the first stages of a burned valve. But, you might not have another stuck valve for 500 hours, it's hard to tell.

[N170BP]

Thanks for the replies and advice folks.

I have a number of options (been doing some interesting
reading about AvBlend and the history behind it), but
needless to say, I'll have to use car-gas and/or MMO
and/or TCP or AvBlend or some bizarre mixture of them all.

I obtained a gallon of TCP for the interim, and have cleaned
the exhaust valves/guides on the right bank of cylinders (still
have to do the left bank). The #3 exhaust valve was free
(no sticking tendency at all) but the #1, while not strictly
stuck, was a little bit on the stiff side. There may be some
kind of issue with the #5 cylinder as that one was "good 'n
stuck". I checked it again after several hours of flying and
it's still free for the time being. The plan is to keep close tabs
on the compression of #5 cylinder and if it starts deteriorating,
I'll just pull that jug and fix it.

I've spoken with numerous "old-timers" (round engine guys,
mostly) and they've used the valve-stem as a hone (spun
the valve in the guide with some kind of penetrating oil)
with very good to fantastic results. My line of thinking is
the valve stem itself should be (?) much harder than the
carbon and/or lead deposits that may be there, so the
latter will "give" when it comes to cleaning the guides out.

The other thought I have is I recognize it's rare to take one
of these engines to TBO without some kind of attention
to the top end (especially running 100LL through them
exclusively). Fortunately, the bottom ends are bullet-proof!

[Jeff Palmer]

I had a friend who had a valve stick 15 years ago. The airport where he landed had a mechanic who helped him do the rope. The mechanic recomended Mix-I-Go. We've been using it ever since. Neither has had a valve stick yet. My mechanic cannot believe how clean my plugs stay either. Great stuff. http://www.belladditives.com/store/inde ... revstart=0

[N1277D]

The MSDS on MIX-I-GO shows that it is Stoddard Solvent

http://www.setonresourcecenter.com/msds ... d0079f.htm

[GAHorn]

I used MMO in the gas of my former 170, on recommendation of my old mechanic who had been flying since the 1920's, for seven years and never had a stuck valve. I did not use it in the oil. I currently use it in the gas in my current 180 though I don't use it with every tank. I run both 100 ll and auto fuel depending on which is available. In the winter when I am not flying much I use only 100 ll as I don't believe auto fuel has a good shelf life sitting. George I know you and the FAA call MMO snake oil but I believe it works.

Harold
N92CP

Uhmmmm....I don't know if I've called it "snake oil" exactly, but I don't think the FAA does either. I think the FAA's position is only that it is an un-approved product for use in aircraft engine fuel/lubrication systems. I believe they allow it to lubricate door hinges.

[N1277D]

A quick check on the MSDS indicates that MMO is also mostly Stoddard Solvent, currently they are owned by the same guys that make Turtle Wax. I was told that the best solvent for clearing up sticking valves and clearing out carbon in the old Porsche air cooled engines is called Techron (spelling) by Chevron. The additive is also found in their gasoline but at much lower concentrations that that found in their off the shelf bottles of it.

[cessna170bdriver]

Everyone's mileage seems to vary concerning the mogas/100LL and MMO/not MMO question. My experience has been that while using straight 100LL I've never had a stuck valve, stuck rings, or a fouled plug that couldn't be cleared with a full power runup.

While using the 2oz MMO in 10 gallons of mogas mixture, I had 3 stuck valves and numerous instances of low compression due to stuck rings (all due to carbon build-up). Also, the exhaust always ran sooty, regardless of leaning procedure. I still have the mogas STC on my airplane, but for the last 9 years have run straight 100LL, and would consider use of mogas an emergency procedure.

I wonder if 100LL were 50 cents/gallon cheaper than mogas, how many would still swear by mogas?

Miles

Standing by for incoming.

[zero.one.victor]

Well, after 1356 hours behind a C-145 (783 SMOH) I can no longer say I've never had a stuck valve!
Started running terrible immediately after start-up yesterday. I had an idea what was wrong, and touch-tested for a cool cylinder. Turned out the exhaust valve on #1 was stuck open. I did the "rope trick", buttoned things up, and immediately after start-up it stuck again.
So last night I read up on the subject (including here on the Assn forums), talked to some friends who've been thru this, borrowed a couple tools, and tore into it today.
Did the rope trick again,compressed the valve spring, dropped the valve into the cylinder (it needed to be drifted out with a brass punch), and reamed the exhaust guide. I figured the ream would remove carbon, but instead it removed a shocking amount of mainly bronze guide material. I was told this would be the case, but it was still a little surprising. I tied a string (actually dental floss) to the valve stem which helped in fishing it back into the guide.
The stuff I borrowed were a valve-spring compressor, a .437" reamer, and a bore light which I could put thru a spark-plug hole, to illuminate things in there. It went pretty well, but still took over 2 hours to do the job (I'm a slow but methodical mechanic). I thought about doing all 6 exhaust guiides, but am too lazy. I'll give it some more thought this winter, when the fine summer weather doesn't beckon me skyward.
BTW, this stuck valve happened the day after I returned from a trip down into Oregon on which I had to run a big slug of unblended 100LL thru it. Probably unrelated but sure is suspicious.

Eric