Why Valves Stick

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.

[altonrowell]

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.

[jsclipper]

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.

[dougmackenzie]

45+ 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!

[michaeljohn]

Thank you very much Mr. Busch. I never new how much of a geek I am. 😂

[SuperYellowsubmarin]

Mike : explains the cause is in the fuel and not the oil.

Audience : proceeds to repeatedly ask what can be done with the oil

[jamesflies]

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!

[stevenschmidt]

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.

[dimsler]

Can we do a presentation on MOGAS and STCs, and effects on the engine, especially the IO520 stc?

[robertkeaney]

A link to this came from a friend. Excellent information on valve sticking and what REALLY causes it.

[alexmelia]

Watch this video at 1.25x speed. You're welcome

[cyl]

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.

[jscott]

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.

[johnrideout]

Would molyslip lubricants ensure that valve stems and guides along with piston rings were less likely to seize?

[Steve_with_coffee]

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.

[pinkdispatcher]

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 :)

[theeatonskbunk]

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

[Iseeuandwatch]

Love this, very educational and well prepared, Thanks.

[tomedgar]

Love the comment on marvel mystery oil, several of the pilots at my airport add marvel mystery oil to their fuel.

[firstielasty]

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.

[jimmywalton]

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).