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The Sticking Valve Syndome

Bill.Peyton

Well Known Member
The Sticking Valve Syndrome

I thought I would post this in the RV10 list since it applies to the IO540 D4A5 typically installed in the RV10, although feel free to move it.

About a week ago I noticed a slight miss/stumble during climb out. This occurred twice, but not on every climb out. It would only occur for a split second during the climb out, but did not occur during the cruise portion of the flight. Along with this symptom, during normal cruise I noticed a slight vibration that felt similar to a prop just slightly out of balance. You could see it in the glare shield. I downloaded the EFIS data from both occurrences and examined it looking for signs of something amiss. I knew the exact time of the anomaly, but it did not show in the data either because the sample rate was to coarse (1Hz) or it was not enough of an event to show up in the EGT, CHT, FF, FP etc.

After reading another post of a catastrophic valve sticking in an RV10, and then thinking back to another aircraft I owned with a Lycoming 360 having experienced a severe valve sticking. The more I thought about it the more I became was convinced that this too was sticking valve. Lycoming has a service bulletin addressing the inspection of the exhaust valve guides at 400 hour intervals, SB333C. I decided to perform the Lycoming Service Instruction No. 1425A which provides a suggested procedure to perform the action. Mike Bullock has a great write up with photos in this post http://www.vansairforce.com/community/showthread.php?t=128673 . I had all the tools including the ream from the last time I performed this task over 10 years ago on the 360.

I was correct in my assessment. Cylinders 3, 4, 5, and 6 all showed evidence of a very slight "interference" fit" and would not pass the Lycoming wobble test. The .4995" ream required a little coaxing to get started in the guides, cylinder 5 was the tightest. I completed the operation on all six exhaust guides in about 9 hours and flew it the next day.

With the 360, I religiously add TCP, a lead scavenger, to the fuel every time I fuel up. I put an additional 1400 more hours on the 360 without any issues, then replaced the engine at 2100 hrs with a Lycoming OH and have flown another 1200 hours without issue on the new engine. I'm going to start using the TCP with the 540.

After 2 hours over 4 flights I feel confident the issue was indeed the beginnings of the sticking valve syndrome. I will be flying a long trip on Monday and hope to report a continued clean bill of health.

Here are the stats on my engine and operation:

- Factory new D4A5
- 411 hours since installation
- Magneto ignition
- 90% of time accumulated is cross country
- All X/C flights are run LOP
- Phillips XC 20W-50
- Camguard additive
- CHT's never allowed to exceed 400 deg.,normal ops I see 310-360


One thing to add to this is that during the break in period I had a high amount of oil consumption. This continued through around 50 hours before it stabilized at a Qt. every 15 hours.
 
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Bill

Great write up more people need to do the wobble test at 400 hours, I have seen alot of planes have this issue over the years and to have 2 write ups in one week on VAF it tells me there are more to be found if people would look.

It will extend the life of the motor, and a good possibility to preventing a off field landing or worse a fatal accident.

Preventive maintenance is so extremely important.

Matter of fact I will do a talk at my next EAA Chapter meeting about this, for our plane owners.
 
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Marvel mystery oil

My O-360 has never stumbled again since using recomendid amount of Marvel Mystery oil in the gas .
 
That sounds right Bill. You coked it on break-in, I'd bet. If your spark plugs have good color now you probably will be good for a long time.
 
I remember Alan Barrett telling me about something that they do in all their engine projects that results in them having far fewer incidences of this problem than stock setups. As I recall, it can only be done on experimental, but I could be mistaken.

I just don't remember the details of what it was that they do. Anybody know the details?
 
Sticking valves.

Bill,
Check and see if you if your cylinders are marked with the number 3 with a circle around it. You can find this mark on the top of each cylinder on the bottom left hand corner next to the valve cover near the drain tube.

If a circle with the number 3 is stamped in this location then the SB referred to above does not apply. Now if you do have this symbol and still have a valve sticking problem then obviously something else is going on.

I now have 685 hours on my engine and it continues to run great. I run mine exactly the same way you do yours with mostly long cross country flights and always LOP. The only difference is that I use Aeroshell W100 Plus with no other additives.
 
No!

Bill,
Check and see if you if your cylinders are marked with the number 3 with a circle around it. You can find this mark on the top of each cylinder on the bottom left hand corner next to the valve cover near the drain tube.

If a circle with the number 3 is stamped in this location then the SB referred to above does not apply. Now if you do have this symbol and still have a valve sticking problem then obviously something else is going on.

I now have 685 hours on my engine and it continues to run great. I run mine exactly the same way you do yours with mostly long cross country flights and always LOP. The only difference is that I use Aeroshell W100 Plus with no other additives.

Don't do the above, read the Lycoming documents carefully instead. :)

SI 1485A calls for a letter "C" in a circle stamped on the cylinder boss for the drain back fitting.

http://www.caa.si/fileadmin/user_upload/pageuploads/AD-NOTE/AD-2006/093_sb_SI1485A.pdf

And in answer to a previous question I had, ECI cylinders have the same markings

http://eci.aero/pdf/03-11.pdf

Superior says to follow the Lycoming instructions and also provide Hi-Chrome guides

http://www.superiorairparts.com/downloads/serviceletters/L00-21.pdf

The dates look like 1998 for Lycoming, 1999 for Superior and 2003 for ECI for the new hi-chrome guides, but the presence of the stamped marking is the key.

As always, RTM :rolleyes:
 
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According to the SB, all cylinders manufactured after 1998 use the newer "C" guide. This was a factory new engine in 2011. I would conclude that it must have the newer guide. I will check next time the cowling is off to be sure.
I suspect that the excessive amount of oil usage, 1 qt every 5 hours, during break-in and for at least 50 hours after that, could have caused this premature accumulation around the guides.

The fact that the hesitation is no longer is further evidence that the guide was the issue. With all compressions being greater than 76/80, I don't believe that I have a burned valve or seat. I will give it a few more hours before I pronounce this totally resolved.
 
i had my mechanic do the 388 SB on the exhaust valves. it took him an hour to do it. i had everything ready for him. $80 well spent. all measurements were wiithin tolerences.
IMG_0993.jpg
 
Cylinder identification

I stand corrected! It is the "C" stamped in the location mentioned above that indicates the "Hi-Chrome" content in the valve guides. I got my information from an "engine man" at a well known engine re-builder, which proves once again that event "Experts" get it wrong once in a while. I suspect that he just misspoke but I will try to find out what the circled "3" stands for.

In any event, Bill's original post as well as subsequent posts brought an issue to the fore which we all can benefit from and also links to the correct information.
 
Can someone do a "nice" detailed writeup with big pretty pictures like the other thread, too? :D My head is spinning with the Lycoming instructions. ;)
 
Data

I stand corrected! It is the "C" stamped in the location mentioned above that indicates the "Hi-Chrome" content in the valve guides. I got my information from an "engine man" at a well known engine re-builder, which proves once again that event "Experts" get it wrong once in a while. I suspect that he just misspoke but I will try to find out what the circled "3" stands for.

.....

"3" and "C" sounds like an accent problem, eh....:)

Anyway, it really says that it is best to confirm important data by going back to the manufacturer's data, it was really easy to find with Google - don't do a Tim Allen.
 
Someone asked, so I thought I would create a summary of the Lycoming Sticky Valve Issue.

Lycoming has several Service Instructions dealing with this topic. It has been around a long time. It affects all Lycoming Engines. This issue manifests itself as a miss or hesitation and is the result of a sticking exhaust valve. This does not affect the intake valve. This is due to the Intake Valve being continually flushed with cool fuel and some amount of oil which leaks around the guide. On the intake stroke this material is sucked in around the guide and also through the intake port when the valve is open. This keeps the intake guide relatively immune to build up on the guide. On the other hand, the Exhaust Valve guide gets blasted with hot gasses as it opens to allow the combustion products to exit. These hot gasses help form lead and oil deposits on the guide and on the valve stem external to the guide in the exhaust port. A better explanation of this is contained in Lycoming Service Letter 1425 A. You can read and download it here.... http://www.lycoming.com/Portals/0/t... Reduce the Possibility of Valve Sticking.pdf

Lycoming Service Bulletin 388C describes a procedure whereby the exhaust valve guide-to-stem clearance can be determined using a fixture clamped on the cylinder head. This procedure is non-invasive and designed to identify if you have or may be close to having an issue with a sticking exhaust valve. You can read the procedure and download it here http://www.lycoming.com/Portals/0/t...termine Exhaust Value and Guide Condition.pdf

Sometime in the late nineties, Lycoming redesigned the exhaust guide to address this issue. Lycoming Service Bulletin 485A describes the nature of the redesign and how to identify if you have the newer design. The service bulletin can be read and downloaded here.... http://www.lycoming.com/Portals/0/t... Valve and Guide Identification Procedure.pdf

In summary, Lycoming recommends that you should either have your exhaust guides tested or reamed out at either 400 hours of service for the older guides, or 1000 hours of service if you have the newer designed guides. But.... this does not guarantee that you won't have the issue prior to the aforementioned time in service. If you fail to recognize the slight hesitation or burble and continue to fly without inspection, you run the risk of the valve severely sticking and coming into contact with the piston. This will undoubtedly ruin your day. The key is to recognize the symptom and maintain your engine.

I hope the summary is useful. If anyone finds any errors or omissions please let me know.
 
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Thanks for the summary Bill. A little different story, but not to affect the end, and that is the heat transfer process of the exhaust valve. The exhaust valve is indeed heated by the exhaust gas, and it is cooled by the time on the seat, and through the stem. Neither are good, cool, heat sinks. The guide must have some lubrication, and does pick up oil from the top. It will migrate down the stem, but in most engines that path is cool enough not to coke the oil. In our Lycs/Clones it is not cool enough. While some of the combustion products are deposited on the valve and stem, it is very unlikely that it is the source of these deposits. Most guides have a relief cut in the lower part to shroud the stem and prevent combustion deposits from traveling back up the stem. I have not done measurements on this engine design. The likely cause of the issue is the oil coming down the guide coking and reducing the stem/guide due to the high temperatures in the stem/guide area.

Edit: This is a fundamental engine design issue. The temps caused coking that caused the guides to wear, so they improved the wear resistance of the guides, now they stick because the root cause remains. The root cause is the guide wall temperature is too high. Running LOP, cooler EGTs, and CHT's will certainly help, if not eliminate, the sticking. The challenge will be the break-in conditions. Cool ambients and leaning will help to the point that CHT and cooling is not compromised.

None of this changes the SB and our vigilance to recognize the onset of an issue.
 
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Edit: This is a fundamental engine design issue. The temps caused coking that caused the guides to wear, so they improved the wear resistance of the guides, now they stick because the root cause remains. The root cause is the guide wall temperature is too high. Running LOP, cooler EGTs, and CHT's will certainly help, if not eliminate, the sticking. The challenge will be the break-in conditions. Cool ambients and leaning will help to the point that CHT and cooling is not compromised.

Group...does field experience suggest angle valve engines exhibit less valve sticking?
 
Dan, after working on a few hundred lycs and contis, I'm not sur if I remember sticking on ANY angle valves of either brand.
 
Wow this has been some really valuable information, and something I want to look in to regarding my engine. My understanding is that my engine came from Vans, then was sent to BPE for them to work their magic. Records indicate that they re-worked the engine and installed 9:1 pistons, with a HP boost to somewhere around 285.

Currently the engine has just over 200 hobbs hours, and we notice an occasional miss and roughness. The engine also seems to run smoother when hot.

~Marc
 
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Typically I try for 50 ROP, but have had a couple of overheat issues if I try climbing out on a hot day and don't do a good job of maintaining the airspeed at 130 kts.

I don't believe I'da toll 'em that. ;)
 
Dan,
In my case the newer valve guides didn't really make much of a difference. I have 400+ hours on the engine and still had a slight build up. In my case, I attribute this to the excessive oil consumption during break-in and for the first 50 hours or so. In addition, my number 5 cylinder would routinely get up to 400 on climb out. I now have redesigned the rear baffle plate to allow for better airflow and no longer have the issue to the same extent. Cylinder 5 was also the tightest guide clearance. In all cases, my front two cylinders run 10-15 deg. cooler than the rest. When I passed the reamer through the front two cylinders they were clear and had full clearance.
I did a climb test yesterday to verify one more time, that my issue was indeed a sticking valve. I kept the CHT's just under 390 all the way up to 7K feet at full power with no issues. I normally would not climb at full power, or best angle.
 
So, Ryan had an angle sticker. That's one. I don't claim they don't stick, just that I haven't seen any to remember. Leak for sure, 470's suck.
 
I thought I would post this in the RV10 list since it applies to the IO540 D4A5 typically installed in the RV10, although feel free to move it.


Lycoming Service Letter No. L197A (Supersedes Service Letter No. L197) January 19, 1988 (http://www.lycoming.com/Portals/0/t... (01-19-1988)/Recommendations to Avoid Valve%) details a few techniques to minimize valve sticking, including not taxiing at idle and running up the engine to 1800 rpm before shut down.

-John
 
Does anybody actually do this?

The second last paragraph of the Service Letter:
"Prior to engine shut-down, the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilized. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds, then reduced to 1000-1200 RPM and shut-down immediately using the mix- ture control."

I'm just wondering about the practicality of using run-up power for 20 seconds immediately prior to shut-down when you've taxied to transient parking and you're blowing debris all over the ramp...it's bad enough when people goose the throttle to pirouette into the parking spot but even that ain't run-up power:eek: Doing this in the hangar rows would also not win you a lot of friends...
 
At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds, then reduced to 1000-1200 RPM and shut-down immediately using the mixture control."

I'd love to hear the technical reason.

I'm just wondering about the practicality of using run-up power for 20 seconds immediately prior to shut-down when you've taxied to transient parking and you're blowing debris all over the ramp...

That's been a constant problem with operators of the M-14 radial. They have a legit reason, but I'll bet a Lycoming user gets cussed....
 
I'd love to hear the technical reason.

Ethylene dibromide

That's been a constant problem with operators of the M-14 radial. They have a legit reason, but I'll bet a Lycoming user gets cussed....

Here is the Shell answer man explanation - it sounds just like the wording of the Lycoming SB.

http://www.shell.com/global/product...centre/technical-talk/techart18-30071600.html

I have no personal experience, just looked it up. It sounds like more of an assumed root cause and an assumed solution to the temperature issue.
 
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I've been operating my new IO-360B1B for about 625 hours. (Fixed pitch prop)

I've never experience any lead fouling until I started working on getting my Instrument Rating going again. It's hard to avoid the prolonged low power settings during approaches and it's really tough coming IFR over the mountains at 10,000 ft and to get down to even start the approach.

I have now upped my spark plug cleaning and rotation to 40 hour intervals when I change my oil.

I've also started running it up to 1800 for a bit before shutdown. (I only do this when there aren't planes, vehicles, or people behind me.)

While I have the airplane apart I have also decided to check my exhaust valves for any stickyness. So far so good but I have 2 to go. (I do have the newer valve guides "C" in a circle but decided to check anyway.)
 
Here is the Shell answer man explanation - it sounds just like the wording of the Lycoming SB.

Thanks Bill! It is an interesting explanation.

I note that leaning for taxi would not by itself raise temperatures as noted.

Mighty tough to taxi an RV at 1200 RPM. If the explanation is true, there should be a correlation between long taxi times and sticking. Any field reports along that line?
 
I usually bring RPMs only up to 1200. Not sure higher rpms are needed. I can get EGTs up to 1200 to 1300F by leaning slowly. Then pull mixture when it gets rough.
 
I thought I would post this in the RV10 list since it applies to the IO540 D4A5 typically installed in the RV10, although feel free to move it.


Lycoming Service Letter No. L197A (Supersedes Service Letter No. L197) January 19, 1988 (http://www.lycoming.com/Portals/0/t... (01-19-1988)/Recommendations to Avoid Valve%) details a few techniques to minimize valve sticking, including not taxiing at idle and running up the engine to 1800 rpm before shut down.

-John


Not sure of the publication dates, but the Lycoming Flyer Key Reprints also talks about operation to reduce valve sticking, yet does not mention the 1800 rpm bit...

It is always best to reduce power in increments so that engine
temperature changes will occur gradually. It is also
beneficial to continue the engine cooling process after
landing by insuring that several minutes of engine operation
at 800 to 1200 RPM are allowed before shut down. At large
airports this is usually accomplished by the time taxi to the
parking area is completed. At airports where clearing the
runway puts the aircraft in the parking area, a short period of
additional operation in the 800 to 1200 RPM range prior to
engine shut down will allow temperatures to stabilize.


http://11hc.44rf.com/manuals/engine-prop/lycoming/lycoming---flyer_key_reprints.pdf

Around page 54
 
Thanks Bill! It is an interesting explanation.

I note that leaning for taxi would not by itself raise temperatures as noted.

Mighty tough to taxi an RV at 1200 RPM. If the explanation is true, there should be a correlation between long taxi times and sticking. Any field reports along that line?

I don't think we are just talking about leaning for temp, although that would greatly help. The actual peak combustion chamber temperatures are quite low at low manifold pressures (relative to 27"). Once, I was checking a 1967 Alfa Romeo Spider with 45 DOCE Weber carbs. It would not idle smooth enough for me. I had the bright idea of testing compression with the engine running. At a dead idle condition, the compression pressure was only 40 PSI. I would discharge the gage, and watch 6-8 counts as the pressure came up and peaked. Compare that to 170psi with the throttles open (not running) for 10: Cr. . Now think about the peak pressure of combustion and temps produced. I don't know what 1800 rpm manifold pressure is, but way higher than 900 rpm idle. I wish they had talked about the actual temperature needed for the lead bromide reaction, that would help.

The rest of the story: The DOCE's (one butterfly, one venturi, and one float per cylinder)have air volume and mixture adjustment at idle, in addition to throttle plate adjustments. By getting the air balanced, then the mixture tuned that throat in. Purred like a kitten.
 
I found this thread because the current owner of my RV-8A (with parallel valve O-360) recently had a rough running engine and noticed it wasn't making full power during a formation takeoff. Local mechanic pulled the valve covers and the #1 valve is in bad shape, discolored and wobbly indicating significant guide wear. A couple other exhaust valves also indicate signs of wear. The airplane has been well maintained and flown regularly. Engine has 850 hrs on an Aerosport Power overhaul (new exhaust valves and guides installed at overhaul in 2002). It has dual Lightspeed ignition so CHTs run a bit hotter than they would with mags (typical of any elec ignition system), but not out of line with other RVs using stock engine/cowl arrangement. Using Exxon Elite 20W50 oil.

Group...does field experience suggest angle valve engines exhibit less valve sticking?

Poking around on the internet I found this article which is over 20 years old but a good overview of Lycoming valve issues:

https://www.aopa.org/news-and-media/all-news/1997/february/pilot/airframe-and-powerplant

The article notes (related to DanH's question above) that parallel valve engines are more likely to have issues than angle valve engines. This is of interest to me as I'm building a -14A that will get an angle valve engine...but I'm still scratching my head as to why some folks with parallel valve engines have no issues running to TBO, and other (like my -8A) develop problems. The local A&P suggests not only doing the 400 hr 'wobble test' (Lycoming SB 333C) but actually reaming the exhaust valve guides every 400 hrs just as preventative maintenance on the O-360 (even if it passes the wobble test). Is anybody out there doing this?
 
I found this thread because the current owner of my RV-8A (with parallel valve O-360) recently had a rough running engine and noticed it wasn't making full power during a formation takeoff. Local mechanic pulled the valve covers and the #1 valve is in bad shape, discolored and wobbly indicating significant guide wear. A couple other exhaust valves also indicate signs of wear. The airplane has been well maintained and flown regularly. Engine has 850 hrs on an Aerosport Power overhaul (new exhaust valves and guides installed at overhaul in 2002). It has dual Lightspeed ignition so CHTs run a bit hotter than they would with mags (typical of any elec ignition system), but not out of line with other RVs using stock engine/cowl arrangement. Using Exxon Elite 20W50 oil.

Poking around on the internet I found this article which is over 20 years old but a good overview of Lycoming valve issues:

https://www.aopa.org/news-and-media/all-news/1997/february/pilot/airframe-and-powerplant

The article notes (related to DanH's question above) that parallel valve engines are more likely to have issues than angle valve engines. This is of interest to me as I'm building a -14A that will get an angle valve engine...but I'm still scratching my head as to why some folks with parallel valve engines have no issues running to TBO, and other (like my -8A) develop problems. The local A&P suggests not only doing the 400 hr 'wobble test' (Lycoming SB 333C) but actually reaming the exhaust valve guides every 400 hrs just as preventative maintenance on the O-360 (even if it passes the wobble test). Is anybody out there doing this?

We should note that there are different problems here. With sticking valves, it is caused by oil coking and sticking to the valve guide, reducing clearance. It is usually from excess heat on the valve, though one could argue that reduced oil flow can accelerate the issue as increased flow takes heat out of the valve.

Your problem outlined above, excessive valve guide wear/clearance, is different and typically caused by different conditions. Oil starvation is one reason, though there are several others, including bad geometry.

Larry
 
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