Lycoming valve sticking

[4RNB]

I recently watched a Social Flight tube video where he and Mike Busch talked about reducing maintenance induced failures. Near the end they talked about lycoming valves sticking, I think referenced SB 388. I think they advocated borescopes every 50 hours to monitor exhaust valves for problems, then ignoring wobble tests and just lapping the valve with the cylinder in place.

SB388 seems to state that the lapping ought be done every 400 hours for fixed wing, unless the valve guides have been replaced with better material.

I see no record of this being complied with on my lycoming IO540. Should I be lapping the valves every 400 hours?

Have any lycoming valve guides been replaced with better material?

 

[SebIp]

You just mentioned maintenance induced failures. And that guy suggested lapping in place which is to me the weirdest suggestion he’s ever made. I mean where does the excess lapping compound and metal bits goes? They cans clean it but some of it get into the engine for sure.

Also lapping that dude suggests is for the valve seal not the guide and rotator which is where the stuck valve issues originate. Lapping is for recovery of seals you still need to fix the stuck not rotating part.

If there isn’t a real problem don’t find one by accident.

Most engines have the new valve guides.

 

[4RNB]

You just mentioned maintenance induced failures. And that guy suggested lapping in place which is to me the weirdest suggestion he’s ever made. I mean where does the excess lapping compound and metal bits goes? They cans clean it but some of it get into the engine for sure.

Also lapping that dude suggests is for the valve seal not the guide and rotator which is where the stuck valve issues originate. Lapping is for recovery of seals you still need to fix the stuck not rotating part.

If there isn’t a real problem don’t find one by accident.

Most engines have the new valve guides.

Lycoming Service Instruction 1425 seems to cover this, so it comes from the source.

Service Instruction No. 1425 A

(Supersedes Service Instruction No. 1425) DATE: January 19, 1988 MODELS AFFECTED All Textron Lycoming Reciprocating Engines. TIME OF COMPLIANCE As required.

www.lycoming.com

(EDIT: looks like this is just to ream things out, not the lapping)

 

[SebIp]

Exactly who would suggest you put abrasive compounds in your engine.

 

[Jim K]

Conflating a couple different issues. The wobble test checks valve stem to guide clearance. Usually this gets tighter over time due to carbon/ lead deposits. That's fixed by removing the valve and reaming the guide.

Borescoping every time you have the plugs out allows you to keep an eye on the exhaust valve. If it shows signs of getting hot on one side, lapping is a way to save it before it fails. Lapping involves putting an abrasive paste on the sealing surface of the valve and spinning it to mate the two surfaces. Mike's assertion is that lapping the valve with the cylinder in situ is safer than removing it.

As for where the leftover lapping compound goes.... out the exhaust as soon as you start the engine. Any tiny amount of abrasive that gets loose is inconsequential. Every looked in a cylinder of an engine running on 100LL? There's a lot of nasty crap in there.

Lycoming switched to the harder valve guide material in 1996ish, so if your engine has been overhauled since then, you should have them. Paul New, who co-hosts the "ask the a&p's" podcast with Mike, had mentioned that he usually doesn't bother with the wobble test and just pre-emptively reams the guides at 1000 hours.

I'd be more worried about the material reamed from the valve guide than valve lapping compound, but reaming guides with the cylinder on is exactly what lyco tells you to do.

 

[Dana]

SB388 seems to state that the lapping ought be done every 400 hours for fixed wing, unless the valve guides have been replaced with better material.

SB388 says nothing about lapping; it's just an inspection of the valve guides by measuring wobble. I haven't seen the video, but at @SebIp says lapping is to address valve sealing issues, not valve guide wear. Many A&Ps don't check for wobble unless the engine exhibits signs of valve sticking like "morning sickness".

However, for seal issues, lapping in place is a time tested way to fix a leaky valve if it's not too bad, and saves having to do much more invasive work. A minuscule amount of lapping compound is used. After the procedure, you clean and blow it out and anything that's left goes out the exhaust during the first few revolutions. I did it on my O-290; it brought compressions back up from 30s to 70s.

 

[Sac Arrow]

I had that issue. The A&P fixed it without a teardown by removing the plugs, pushing the valves in to the combustion chamber, then fishing the stems out the plug holes with a grabber and cleaning the lead deposits and reinstalling them with the grabber. It sounded like a lot of work, but the price wasn't too bad and it fixed the problem.

 

[Dan Thomas]

Exactly who would suggest you put abrasive compounds in your engine.

It's an old, old trick. and I've done it. One has to be really careful, but it's possible.

 

[Rcmutz]

I had a stuck valve on my O-360. The AnP/IA used the rope trick to push the exhaust valve in and reamed the guide. Did this on all 4 cylinders and also checked/IRAN the hydraulic plungers. She Lycoming SI 1011N Jan 7, 2019.

 

[Skymac]

Usually my experience show they are due a ream around 1000 hours and if you just do it, or do it once you see a compression below 65-68 then that cylinder will keep giving many years or good service. Ream and then light lap, doesn’t take much.

 

[Clip4]

I recently watched a Social Flight tube video where he and Mike Busch talked about reducing maintenance induced failures. Near the end they talked about lycoming valves sticking, I think referenced SB 388. I think they advocated borescopes every 50 hours to monitor exhaust valves for problems, then ignoring wobble tests and just lapping the valve with the cylinder in place.

SB388 seems to state that the lapping ought be done every 400 hours for fixed wing, unless the valve guides have been replaced with better material.

I see no record of this being complied with on my lycoming IO540. Should I be lapping the valves every 400 hours?

Have any lycoming valve guides been replaced with better material?

Yes, Mike Is an idiot.

 

[Domenick]

I had a stuck valve on my O-360. The AnP/IA used the rope trick to push the exhaust valve in and reamed the guide. Did this on all 4 cylinders and also checked/IRAN the hydraulic plungers. She Lycoming SI 1011N Jan 7, 2019.

Dropbox

www.dropbox.com

 

[tms2x2]

I recently watched a Social Flight tube video where he and Mike Busch talked about reducing maintenance induced failures. Near the end they talked about lycoming valves sticking, I think referenced SB 388. I think they advocated borescopes every 50 hours to monitor exhaust valves for problems, then ignoring wobble tests and just lapping the valve with the cylinder in place.

SB388 seems to state that the lapping ought be done every 400 hours for fixed wing, unless the valve guides have been replaced with better material.

I see no record of this being complied with on my lycoming IO540. Should I be lapping the valves every 400 hours?

Have any lycoming valve guides been replaced with better material?

I had a club plane Cessna 172 that stuck a valve in flight with 600 hours since overhaul. A 182 that stuck a valve at 800 hours. Both engines had to be overhauled. The oil filters were full of metal by the time they landed. They both had the updated valve guide material. There is a letter C in a circle above the rocker drain fitting on the cylinder to designate the change. I recommend doing the inspection for valve wobble SB388 at 400 or so interval. I usually find valves that are worn more than specification. Not too many that require reaming. The lapping of the valve is only to address a low compression test.

 

[Lama1125]

Yes, Mike Is an idiot.

Dealt with a bunch of people who think his word is law, too? Crazy how many people drink the fruit punch.

 

[Dana]

Dealt with a bunch of people who think his word is law, too? Crazy how many people drink the fruit punch.

He's not an idiot, nor is he God. Some of what he says is worth listening to. What's truly crazy is how many people can't see shades of gray, or that a person can be wrong about one thing without being wrong about everything (and vice versa).

 

[pfarber]

Dealt with a bunch of people who think his word is law, too? Crazy how many people drink the fruit punch.

Whats hilarious is that people think SBs are there to save THEM. SBs are to save the manufacturer from liability.

Also I like that you offered nothing but your own bias.

OP may also not be recalling the episode correctly. Lapping valves and reaming valve guides solve two very different problems on the modern 1940's marvels (lol).

 

[Dan Thomas]

Whats hilarious is that people think SBs are there to save THEM. SBs are to save the manufacturer from liability.

And the end result is exactly the same for both. The SB warns the owner of a safety issue. He can choose to fix it, or ignore it at his own peril.

Bias? Your biases are in almost every post.

 

[Bell206]

He's not an idiot, nor is he God. Some of what he says is worth listening to.

Definitely. But the main amusement comes from he has made a good living by repackaging, rebranding, and selling readily available maintenance information even though he never made a living as a mechanic. PT Barnum would be proud.

Whats hilarious is that people think SBs are there to save THEM. SBs are to save the manufacturer from liability.

Whats more hilarious, is you really don't have a clue how the mx system works. As I've said, you're better off sticking to trashing CFIs.

 

[pfarber]

Bias? Your biases are in almost every post.

No, not at all. The vast majority of my posts are cited and have facts (maths are fun!)

Having a different answer is not a bias.

 

[pfarber]

The SB warns the owner of a safety issue.

If it were a safety issue it would be an AD REQUIRING its performance. That's why God created the AD.

Lycoming HAS initiated ADs... the most recent being AD 2024‑21‑02 that started as a simply, lowly, ignored SB. Wanna know why SB 632 was written? To protect it from liability regarding parts they installed.

This AD is for lycoming overhauled engines that they botched.

If there was a serious safety concern why didn't they go straight to the FAA?? Because they hoped that it wouldn't be a problem. Evidently the beancounters said it is, so they notified.

If you are niave enough to think that Lycoming is gonna do what's in YOUR best interest then ok, run with that.

 

[Kelvin Matthews]

If it were a safety issue it would be an AD REQUIRING its performance. That's why God created the AD.

Lycoming HAS initiated ADs... the most recent being AD 2024‑21‑02 that started as a simply, lowly, ignored SB. Wanna know why SB 632 was written? To protect it from liability regarding parts they installed.

This AD is for lycoming overhauled engines that they botched.

If there was a serious safety concern why didn't they go straight to the FAA?? Because they hoped that it wouldn't be a problem. Evidently the beancounters said it is, so they notified.

If you are niave enough to think that Lycoming is gonna do what's in YOUR best interest then ok, run with that.

You are wrong sir, the majority of AD’s come from service bulletins and in the majority of cases the SB’s bulletins are meant to address a “safety issue” according to the manufacturer that’s why they are mandatory in commercial aviation, when it’s has the red lettering like “mandatory” that’s the manufacturers telling you we want the faa to really really really make this an AD but they don’t want too.
That is the way the system is setup to work and at the end of the day is about safety and you are right liability but that doesn’t mean it should taken likely. We should not totally ignore them before that arrow went down in Florida that started the piper wing spar AD that was already a SB addressing that issue and calling for inspections of the piper wings. Should SB be made mandatory in the US? I don’t think so but we should not ignore them.

https://www.faa.gov/sites/faa.gov/files/2022-01/Service%20Bulletins%20and%20the%20Aircraft%20Owner.pdf

 

[Dave Palacios]

You just mentioned maintenance induced failures. And that guy suggested lapping in place which is to me the weirdest suggestion he’s ever made. I mean where does the excess lapping compound and metal bits goes? They cans clean it but some of it get into the engine for sure.

Also lapping that dude suggests is for the valve seal not the guide and rotator which is where the stuck valve issues originate. Lapping is for recovery of seals you still need to fix the stuck not rotating part.

If there isn’t a real problem don’t find one by accident.

Most engines have the new valve guides.

You or he may have goten the two procedures mixed up, you are correct lapping is for valve seating with the valve seat and reaming the guide is for removing carbon and maybe cooked oil between the valve stem and guide. As for performing these without removing the cylinder, I myself have not done these but more and more i hear of people doing it. So its more comon than you think. As for contamination, cleaning is done after and shop air is blasted through the spark plug hole and possibly, simultaneously , a vacuum is applied on the opposite spark plug hole. Any trace of compound that remains is purged out with the exhaust. Not much of a chance of damage to the engine. what i have done was to investigate a rough engine and found the cause to be a portion (about a 3/4" in sze) of the discharge nozzle of the carb broke off and was ingested. i searched for the piece with a borescope but it was gone !! it was blown out the exhaust port of one of the cylinders. Being made of somewhat soft bronze material no damage was done fortunately. The reaming and the rope trick should only be done by a mechanic who knows what they are doing. I had to completely disassemble a cmc o-300 because the owner was doing the rope trick and broke one of the lifter bodies trying to reassemble (he was an a&p but had been retired for some time) So if it isn't broke don't fix it.

 

[Dan Thomas]

No, not at all. The vast majority of my posts are cited and have facts (maths are fun!)

And yet it's so easy to find and post reliable info that proves you are wrong. Many, many times.

 

[Lindberg]

Wanna know why SB 632 was written? To protect it from liability regarding parts they installed.

How does it do that?

 

[Half Fast]

But the main amusement comes from he has made a good living by repackaging, rebranding, and selling readily available maintenance information even though he never made a living as a mechanic.

I have a copy of the Light Plane Maintenance Library, published back in the 1980s. About 80% of Mike's magic fixes can be found in those pages. Our Lycomings and Continentals are very old designs and have very old problems with very old solutions.

Much of what Mike says is okay (with occasional bungles), but he's not Moses descending the mountain with tablets from the Almighty. He's just a popular evangelist preaching from ancient texts (and with the marketing skills of a modern televangelist).

 

[FastEddieB]

I had a stuck valve on my O-360. The AnP/IA used the rope trick to push the exhaust valve in and reamed the guide.

This was the fix on my Tiger after an emergency landing on Long Island.

Had no issues in the remaining years I owned the plane.

 

[Domenick]

I have a copy of the Light Plane Maintenance Library, published back in the 1980s. About 80% of Mike's magic fixes can be found in those pages. Our Lycomings and Continentals are very old designs and have very old problems with very old solutions. ...

I got into Light Plane Maintenance rather late, but recognized the wisdom there in. I scanned every issue from March 2011 to Jan 2013. I indexed each year and collected all the covers into a single file. The covers have the TOC for that issue.

The zip file is 200+ MB. Yours for the downloading:

Dropbox

www.dropbox.com

 

[Magman]

As a former manager of 56 exhaust valves I have wondered why

sticking exhaust valves was not a problem with radial engines?

Even with high lead 115/145 fuel.

 

[Mikey52]

As a former manager of 56 exhaust valves I have wondered why

sticking exhaust valves was not a problem with radial engines?

Even with high lead 115/145 fuel.

Bigger tolerances, thats why they all disposed of engine oil during flight. What they couldn't belch out in the air, they tried to do on the ground or hangar floor. Sometimes i thought they were allergic to it.

 

[Steamflyer]

This was the fix on my Tiger after an emergency landing on Long Island.

Had no issues in the remaining years I owned the plane.

Glad worked out ok. Stuck valves that bend the pushrod to this degree can also damage the camshaft, necessitating IRAN.

 

[Half Fast]

I got into Light Plane Maintenance rather late, but recognized the wisdom there in. I scanned every issue from March 2011 to Jan 2013. I indexed each year and collected all the covers into a single file. The covers have the TOC for that issue.

The zip file is 200+ MB. Yours for the downloading:

Dropbox

www.dropbox.com

Got it! Thanks!

 

[Bell206]

sticking exhaust valves was not a problem with radial engines?

Radials had their share of valve problems as well. As I recall the rope trick mentioned previously started life as the Jacobs Rope Trick since certain models were prone to leaking exhaust valves as well. However, its my understanding the increase in valve issues was mostly due to the shift away from 80 avgas to 100LL being the only option which had a much higher lead content.

 

[Magman]

100LL replacing 80/87 played heck with Intake Valves on O-200’s.

Learned you could pull a jug; address valves and reinstall w/o

doing anything with Rings.