Why Valves Stick
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- čas přidán 8. 08. 2020
- Sticking and stuck exhaust valves are a frequent problem in piston aircraft engines, especially Lycomings. In early stages it manifests itself as roughness after engine start (so-called "morning sickness") and can progress into something much more serious and a significant cause of power-loss incidents and accidents. Conventional wisdom says that it's caused by carbonized oil buildup due to excessive heat. In this webinar, Mike Busch explains that the real culprit is lead, not carbon, and it's actually insufficient heat that's the problem. Proper powerplant management techniques can minimize this problem, and Busch shows you how.
Savvy Aviation offers Professional Maintenance Services to owners of GeneralAviation aircraft, such as: SavvyMx (Professional Maintenance Management), SavvyQA (Expert Consulting), SavvyPrebuy, SavvyAnalysis (Engine Data Analysis) and Breakdown Assistance. Savvy also publishes a monthly newsletter with lots of interesting information for the general aviation enthusiast; subscribe to it at www.savvyaviation.com/home/ge.... For more information, visit us at savvyaviation.com. This webinar was hosted by the Experimental Aircraft Association (EAA). - Auta a dopravní prostředky
Mike : explains the cause is in the fuel and not the oil.
Audience : proceeds to repeatedly ask what can be done with the oil
Additive mfgs market nonstop to confuse as many people as possible.
Fuel and oil touches a valve stem. At around the valve seal operacional range.
I'm a 65 year old life long mechanic that has also taught at the post secondary level for many years where I was privileged to get to hear many seminars from industry professionals on such topics. This is the best I've ever seen/heard on the topic. Thank you for your input.
I'm a 35 year auto mechanic. This video is very interesting stuff. Thanks man. I didn't know about the chemical products in fuel outher than octane additives.
35+ year A&P (heavies), here. This was an excellent presentation! I'll be sure to watch more of Mike's work! Thanks for this critical information!
Watch this video at 1.25x speed. You're welcome
I like 1.5x speed.
Lol....
Can we do a presentation on MOGAS and STCs, and effects on the engine, especially the IO520 stc?
I used Hoppes 9 and a rifle barrel snake to remove the lead oxy-bromides from the valve stem. Worked great. Didn't need to ream the guide because the valve was as free to move as when new.
Thank you very much Mr. Busch. I never new how much of a geek I am. 😂
But honestly I’m going to join your webinars I find them just a wealth of info. I’m a apprentice trying to get my A@P a over at KLZU flight school. I won’t be rude and advertise but suffice to say we run about 20 Lycomings. From the 320,s to the 360;s and this is a major problem that we run into often. This is great info. I’m so happy to have found this webinar. Thank you.
Would just like to say I'm not an A&P, I don't own my own airplane, but I really appreciated this video. I've found that seeing/hearing someone dive deep on a very specific topic, I gain a better understanding of that system (even if it's not nearly to the level of the target audience of the presenter) but also of the related systems. This one was no different. Thank you!
Glad you enjoyed it!
A link to this came from a friend. Excellent information on valve sticking and what REALLY causes it.
Glad it helped
Lycoming recommends the valve and guide inspection in SB388C. It is surprising that the FAA does not (yet) have an AD in this regard, but EASA has derived AD2005-0023R3 from SB388C.
Love this, very educational and well prepared, Thanks.
Great video!
Great video. Thanks! In my SR22 I routinely run CHTs around 380 on climbs, but high 200s to low 300s in cruise. Am I OK with that? I almost always run LOP. I wasn't sure if your suggestion to run higher temps was just for peak CHT temps on climb out or at all times. Thanks.
Super informative ! Thank you guys !
Glad you enjoyed it!
Something approaching 3 decades ago I was flying along the Front Range in a rented aero club 182 with a new rebuilt engine when I experienced vibration so strong I initially thought I'd lost a prop blade. Turns out the shop that had redone the engine had installed at least one undersized exhaust guide, but after watching this I wonder if a parallel issue was deposits. Because the plane was part of the aero club rental fleet and used for complex and mountain checkout and so saw a lot of different leaning technique, and while you're always lean at a mile up I recall lots of people running along the ramp close to full rich. It's fantastic to understand the process behind the issue, but what I find troublesome is how many people still are asking if an oil additive will solve the problem, even after listening to Mike say nothing about oil and everything about fuel and valve temps. It tells me that a lot of us don't know, really, what's happening inside our engines. I have a little bit of an advantage in that I was racing before I was flying and I've rebuilt a number of flat six and flat four Porsche and VW engines (and yup, they operate in very different environments and conditions but the layout is very similar), and so I am always in tune, no pun intended, with my engine, but perhaps we as a community should spend some time on mechanical literacy. You don't need to know how to build an engine or be able to work out a stoichiometric equation, but knowing that the oil and fuel systems are, or should be anyway, completely different systems with little interaction, and a solid grasp of how they work in whatever you're flying. Thoughts? Side note: That 182 had the cold weather oil thinning system wherein you hit a switch and count a few seconds while fuel was injected in to the oil sump. First time, and honestly every time, I did that I just felt dirty.
Would molyslip lubricants ensure that valve stems and guides along with piston rings were less likely to seize?
His comments at 7 minutes, valve sticking closed, just happened to me in my YIO-390. And my pushrod bent along with the shroud (tube).
Terrific learning thank you
Glad it was helpful!
Love the comment on marvel mystery oil, several of the pilots at my airport add marvel mystery oil to their fuel.
I've flown two aircraft with Lycoming O-360, one with a Continental IO-240, and one with a Continental O-200A, and the only one on which I've had sticking valves was the O-200 running on mogas. So I guess I'm the exception that proves the rule :)
Same here. And those Continental deposits did not look like lead or bromide on the PowerPoint slides
The valve stems had minimal deposits
Could there be two different types of deposits and sources/causes?
The TCM deposits were located in the guides, baked onto the wall of the guide.
The valve guide reamer cut through the deposits which were hardened, black, and looked like carbonized oil.
The sodium filled exhaust valves on lycomings help cool the valve HEAD. And do so by improving heat transfer to the stem.
Heat moves from the head, to the stem. The result is a cooler head less prone to burning.
But the stem gets hotter. This is even shown in the Cont. Vs Lyc. valve temp diagram in this video- look close, the Temps high up on the Lycoming stems are higher. The head is shown as cooler.
37:47 best part is MB cracking up !
Is there a solvent that can break down the coating and nat damage the aluminum or valve guide?
No
I have extensive experience in this field and have a few issues with the information (not all) provided. #1 the buildup is in the valve guide not the the valve stem, and is by far more problematic in an injected vs carbureted Lycoming. Lycoming 1425A is a good place to start for Temporarily correcting the sticky valve. Mike should have analyzed the contents removed from the guide not the valve stem to get the complete picture. I have ROUTINELY encountered stuck valves in new Lycoming injected engines with 300-400 hrs operated in the desert southwest (no problem running them above 350 here. I do appreciate all that Mike does and respect his opinions.
Why would the deposit in the guide be different from what is on the stem? Not saying this take is wrong, just that it seems like it would be the same compound. He talks about excessive mixture richness being a problem as well as coolness, and maybe being new was a factor as well.
Thanks Mike, I really find your presentations very informative. Those of us flying piston powered helicopters are reminded to get cylinder temps down and stable before shutting down. Unlike airplanes that taxi back at an idle, helicopters need as much or more power to hover than at max continuous cruise. Failure to do this cool down is said to lead to sticky valves caused by the oil being overheated in the valve guides after the cooling airflow ends. I'm wondering about your thoughts on this.
Thanks again
Thats oil coking, also possible, but the major problem are the top compression piston rings getting heat soaking and coking the oil at ringlands and making ringsticking by the cutoff oil flow. Heads are a bit cooler because of greater cooling contact area and more metal between guides and head metal and oil there, though. But it is still possible to Cook mineral oil. Hence the need to use non ash dispersant and lack of metalic detergents in aircraft oils. Agree that a proper cool down is even more essential for choppers.
@@tomasnokechtesledger1786 Lycoming Service Bulletin no 388C suggests inspecting valve guide condition every 300 hrs in helicopters and 400 hrs in others. I know of machines that have experienced sticking valves, and others that required remediation at inspection time. To my knowledge none of the ones I fly have had issues with compression/ring sealing. Mike argues that the Lycomings valves run too cool. There is a disconnect between this and the service bulletin requiring more frequent inspection on helis. Helis operate at very high power settings just prior to shutdown (hover takes as much or more power than cruise flight, planes taxi back from the runway at idle). It is possible that both views are correct (cooler valves get more deposits, helis shut down quickly after landing have hot valves that coke) and I was hoping to hear Mike's views on that possibility.
Savvy,
If the post combustion lead deposits are an issue, why is straight leaded gasoline needed in such low rpm, low compressions engine's in the first place? 1 gallon of 110 leaded fuel to 4 gallons of gasoline goes a long way in the engines I work with.
I pour a small amount of water into the throttle body of my Honda to clean off carbon. The other day my O-320's carb iced, and when I pulled heat the engine ran rougher, then cleaned up. I wonder if it cleaned the engine at all.
What about vapor lock, is MOGAS more susceptible?
Yes
Mike....I had a stuck (open) exh. valve in my Lycoming 0-235 C-1....I lubricated the valve stem several times and staked the valve over a couple weeks and eventually the stuck valve freed up and finally closed....I again kept lubricating the valve stem with Kroil...I finally started the engine and fast taxied my Citabria for 15-20 minutes....it seemed normal....my question is where do I go from here....how can I rely on this not happening in flight...should I rebuild cylinders or put new Lycoming cylinders....the engine has just a couple hrs.over 2400 hrs. with fairly low compression readings...any advice ??
You aware of being able to take the valve out without removing the cylinder? Using the rope trick? You can then clean the valve stem hanging out the spark plug hole and ream the valve guide. It's all very fiddlying but I've done it on my 0-320. It was only a temporary thing as the cylinder was oily and it had to come off to be honed but it stopped the sticking for the summer and I could then take the cylinder off in the winter (which is the best time to break in when there's no Thermal activity, I flew the engine flat out for a good while). I flew happily with no problems for 100 hrs. I suppose you have to find out why the valve has started to stick as after you've cleaned it up if the problem is still there it will only come back.
I have a #2 cylinder that seems to be make compression twice during the firing cycle, how is this possible?? I had to do an emergency landing because i lost cylinder and thats the most abnormal thing i notice. Any idea?
Do you have a broken push rod or rocker arm on #2's exhaust valve?
Id like to have heard more about not using synthetic oil in a Rotax with 100LL...
The lead sludge is a problem that comes with PAO base oils. Like old Mobil1 Aviation.
Do airplane engines have a hardened valve seat insert? That's why there are so many cars with aluminum heads using unleaded fuel with no problem, because they have them - but older cars designed for leaded fuel don't have them.
Yes, most Lycomings switched to hardened valve seats in the 80s
Cars have water-cooled cold cylinder heads, with the Aircraft Engine cylinder heads running so very much hotter the same metal cannot tolerate operation without the leadoxibromide deposits for very long (100 hours maybe) before a breakdown begins. This is the case even with low compression engines. I totally disagree with Mr.Busch on this point. What works forever unleaded at 200F does not work to TBO at 350 F or 400 F !!!
Pretty interesting. My valves in my 2 Stroke wont be sticking from my 100LL and my 339 CHT ;)
And how about the Rotax?
Can someone answer this for me...
If you have Excellent Compression, IE 78-79/80, is it remotely possible that you have sticking valves? The other Day I think I may have encountered "Morning Sickness" but I'm not sure.
Johnny, its possible that your compression tests were done when the engine was warm (that's the usual approach, to get the "best" reading); Morning Sickness happens when the engine is cold and tolerances are most tight. So to answer your question, yes, it is possible.
@@savvyaviation
Thank you for the answer.
The engine actually was cold when the compression test was completed.
It's a moot point now as the aircraft has since been totaled unfortunately.
Mark, you meant to ask the *minimum* CHT.
Tapping the valve stems on old v 8s with a hammer to find the stuck ones . Good times .
Oddly MMO was created to keep lead out of those beautiful old bronze marvel carbs . I'm sure he meant to put it in the oil tank
Isn’t the transition from a gas to a solid called deposition? In reverse sublimation?
No. Sublimation is used for both transition directions.
I’m one of those who has a front cylinder that runs close to 300°, I can only imagine what my AP will say if I tell him my engine is running too cool.
Good front bafles there?
@@tomasnokechtesledger1786 actually I had a leaking fuel injector, now they all run around 350°
Considering the relatively low compression ratios found in aircraft engines, why would valve strikes be an issue if a valve won't close? Just wondering. I've always figured that aircraft engines should always be non-interference designs.
Caused me engine fail over sierra foothills. Not fun
Years ago when we had leaded car fuel, if you removed a exhaust valve, the hard crust on a exhaust valve was like a hard beige rock type substance. Obviously lead.
I was flying when a valve dropped, put down in a field. Valve punctured piston. The engine had run rough for some time.
Wish for new design to replace the old standards which are poor by todays engine standards! Cylinders and pushrods get to wobble in the block like a VW engine.
Because you don't lean the mixture soon enough as most pilots do that fly over the ocean and never have that problem hope this helps everyone 👍
Auto fuel octane ratings get lower in 3 to 4 weeks, avgas is much more stabile
Mike what about engine using automobile unlead fuel it will created vapor locks
I would not want to run any auto gas that contains ethanol. I have a fleet of motorcycles(22) that are used for training and ethanol does bad things to engines if they aren’t used at least weekly. In California, it is almost impossible to find non ethanol fuel. In other states,it can be found. Every time you purchase a new car, there is a thousand dollars added to the cost in materials to deal with the effects of ethanol.
Lead lubricating valves is not a wife’s tail! I was around in the late 80s when leaded auto gas was phased out. I saw the damage firsthand. There were a large number of cars from the 1960s still on the road these engines didn’t have hardened valve seats. Valves didn’t sink into the head before unleaded gas was forced on us. I still have a few sets of heads around here somewhere that have exhaust valves sunk 1/2 an inch into the head. Sure late model cars have hardened seats and don’t need leaded gas to keep the valves and seats alive. What about GA piston engines? Do they have hardened seats?
so my io470 has a bit of a miss when cold and only if its been sitting for at least a couple of weeks, but doesnt miss if its cold and only been sitting a couple of days, it always passes the compression test at its annual. Engines run cold all the time from start up to warmed up. this theory seems like another doom and gloom worst case Mike Busch scenario.
TEL...still destroying everything it touches. That is some evil stuff.
Einstein was not left-handed.
Rhetorical question: why do aircraft engines need such high compression to get HALF A HORSEPOWER PER CUBIC INCH? Automotive engines with the same compression can get a full horsepower per cubic inch - and the turbocharged engine on my car puts out TWO HORSEPOWER PER CUBIC INCH on 91 octane gas.
Automotive engines operate in a far wider RPM range and make significant power well above aircraft engine RPM limit. What sort of power do you get out of your automotive engine when you limit RPM to 2,700 rpm?
What Kris said, plus the fact that re-engineering the engines is economically stupid. The engine in your car gets sold by the 100,000. The scale-costs of manufacturing aircraft engines don’t cover the liability and certification costs. That’s why experimental planes have become so popular.
@@KenLeonard Sadly, that's why there's no hope for GA.
aircraft engines actually have low compression compared to a modern automotive engine
Sodium fill in vlv was kinda stupid idea?
You are so wrong. Lead reduces valve seat wear.
What did I miss, he discusses build up on the valve stem, what does that have to do with the seat?
@@tomedgar4375 He said lead has no purpose in fuel. I say it lubes the valve seat.
@@michaelsamson3276
got it
does the seat need to be lubed? and if so WHY?
@@markandregg8235 The lead acts as a cushion. For example, cars from the 50-60's need new hard valve seats for unleaded fuel or the seat will pound out.. Aircraft engines with aluminum heads have hard seats already so it's not as big a problem.
Dirty oil, running too hot, poor maintenance. Improper fits and clearances (wear/monkey mechanic), debris working through the engine, not heat….. you’re funny