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I may have a sticky valve

A5555

Well Known Member
no engine roughness after start.... but after takeoff, cylinder #1 CHT and EGT both do not rise with the others for the past couple of flights. it takes cylinder #1 about 5 minutes to "catch up" in temperature to the others. this is different than in the past, where all cylinders would heat up uniformly. I may have a sticky valve on cylinder #1. at 850 hours on the engine, I have never done a wobble test. I have only removed the valve covers once to "look" in there. I read Mike Bullock's "sticking exhaust valve" guide and maybe I can do it. I sent Darrell at Superior a question about proper reamer size for my O-320. Mike used a .4995 for his IO-360. anyway, at least I should learn how to do a wobble test. it seems like the proper thing to do while the Winter weather is rolling in early.
 
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Steve,

Can you upload your engine monitor data to the Savvy site and share the link?
 
I would find it hard to believe that you have a sticking valve without some other indications, like roughness or missing. Any of those symptoms?

Do try some Marvel mystery oil in the oil and the fuel.

Vic
 
I would find it hard to believe that you have a sticking valve without some other indications, like roughness or missing. Any of those symptoms?

Do try some Marvel mystery oil in the oil and the fuel.

Vic

Vic, no roughness or missing that I can detect. I thought about MM oil. I just don't know about it.
 
Lycoming also has a method for "staking" the valve. Basically use the wooden end of a hammer on the valve and pop it a few times with another hammer.
 
No engine roughness... do you lack any power during these first few minutes? Then it gets more powerful? Is it possible you just have a lazy couple of sensors?
 
No engine roughness... do you lack any power during these first few minutes? Then it gets more powerful? Is it possible you just have a lazy couple of sensors?

no engine roughness, no loss of power. the only other thing I noticed is maybe a reduction of 15 rpm or so when I do a mag check on both the left and right mag.
 
I've had a few episodes with sticking a valve. In flight one exhaust valve sticking open,on a 4 cylinder, causes extreme roughness and reduces power by close to half.

I would look elsewhere for the aberrant indications you are seeing...
 
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Steve,
On our 360, we saw that cylinder 1 was coming alive after everyone else, by 10-20 sec or more. Than CHT and EGT would come up as the tHé other one. We took the exhaust valve out, used the ball hone the RocketBob suggested and clean the guides. They were fine and didn’t make any real difference. Than we checked the push rod length, we realized we were out of spec and installled the proper length and everything seams to work now, meaning they all come alive at the same time. I believe that if you have oil in the jug, it might not fire for the first few stroke and than come alive.

Let us know what you find. But if you take those valves out, buy those ball honed, they work great.

Erik
 
After having an airborne exhaust valve failure due to a sticking valve on my old O-360A1A, here are my recommendations:

At 850 hours you are overdue for a "wobble check" (SB 388 C, if memory serves). Valves can be too tight, or too loose in the guides. The check is not invasive, and can be done in an afternoon. If the check passes, you're done. If not, investigate further.

I would also do a good borescope inspection of all the valves. Again, if all good, press on. If not, investigate.

But before you do the expen$ive and difficult stuff, make sure your indications are correct. No sense chasing bogus data.

My 2 cents, and YMMV, etc.
 
Vic, no roughness or missing that I can detect. I thought about MM oil. I just don't know about it.

I would be looking at things that reduce power output in number one. Ignition (plug issue), fuel flow (injector clogging) and compression. I would speculate that #1 is not producing full power.

Larry
 
How do I get Mike Bullocks guide to sticking valves... thanks

For some unlucky reason I seem to be the leading expert in stuck valves since I have had 3 of them. My A&P friend who has been practicing for over 15 has only had to fix one!

My Website

8/2015 - Original Issue - Stuck #2 Cylinder
http://www.rvplane.com/?categoryid=10000&dayid=1263
http://www.rvplane.com/?categoryid=10000&dayid=1264
http://www.rvplane.com/?categoryid=10000&dayid=1265

Improved DIY bracket for valve compressor
http://www.rvplane.com/?categoryid=10000&dayid=1350

I have switched from using the "rope trick" to using compressed air (via differential pressure tester) to keep the valves closed to re-install the spring. There is a slight chance the rope will tie itself in a knot inside the jug, causing you to need to remove it!

7/22/20 - Stuck #4 Cylinder
http://rvplane.com/?categoryid=10000&dayid=1461

Kitplanes

VAF Thread
 
I would find it hard to believe that you have a sticking valve without some other indications, like roughness or missing. Any of those symptoms?

Do try some Marvel mystery oil in the oil and the fuel.

Vic

MMO is just the trick if indeed you have sticking valves as it is an excellent upper cylinder lubricant. I had an Apache with 2100 hr engines that would pop and snort until warmed up after a cold start. 1 qt. MMO in each engine and the problem vanished almost immediately.
 
MMO is just the trick if indeed you have sticking valves as it is an excellent upper cylinder lubricant. I had an Apache with 2100 hr engines that would pop and snort until warmed up after a cold start. 1 qt. MMO in each engine and the problem vanished almost immediately.

I struggle to see how MMO can knock off .005" of coked oil. If it could, they would be the official fix. I can see how it would lubricate and clean just enough for the symptoms to abate. However, the tight guide is still there and without continual MMO use and maybe even with it, you are likely to have the problem return and next time could be a bent pushrod and a very rough ride home on three cylinders.

Better to tackle the problem with reaming and eliminate it for good or at least another 500-1000 hours. I reccomend caution in following this approach for resolution. Morning sickness is a serious symptom that requires immediate attention. This is especially true if you have installed thick walled aftermarket pushrods.

Larry
 
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I had a sticking exhaust valve twice and the symptoms were typical for morning sickness. Only after engine start the offensive cylinder was missing - no rising EGT and CHT and recovered after a while - not after takeoff as discribed here. Turning the prop through when cold the one cylinder had zero compression.
Strange this is showing after takeoff but it might be worth to have a look at the valve guide and do a wobble test.
 
well, I had my share of stuck valves as well, groundborne as well as airborne... and I don't think you have a stuck valve Steve.

Next I'd do, is a compression check: you could have a valve or a valve seat problem which resolves when the engine has reached its proper temperature. Maybe...
 
I struggle to see how MMO can knock off .005" of coked oil. If it could, they would be the official fix. I can see how it would lubricate and clean just enough for the symptoms to abate. However, the tight guide is still there and without continual MMO use and maybe even with it, you are likely to have the problem return and next time could be a bent pushrod and a very rough ride home on three cylinders.

Better to tackle the problem with reaming and eliminate it for good or at least another 500-1000 hours. I reccomend caution in following this approach for resolution. Morning sickness is a serious symptom that requires immediate attention. This is especially true if you have installed thick walled aftermarket pushrods.

Larry

When I was learning to fly, we got a stuck valve on a Continental O-300. Shook so bad, I thought the engine was going to fall off! The old school CFI-A&P-IA owner did the rope trick, used MMO in both gas and oil from then on, and never had another problem with it after that.. flew it for years after that. Idk.. that stuff is a mystery...
 
When I was learning to fly, we got a stuck valve on a Continental O-300. Shook so bad, I thought the engine was going to fall off! The old school CFI-A&P-IA owner did the rope trick, used MMO in both gas and oil from then on, and never had another problem with it after that.. flew it for years after that. Idk.. that stuff is a mystery...

I would speculate that MMO can help prevent the deposits. But I am with your mechanic that MMO alone will not remove it once there.

Larry
 
Reamers dont get everything out of the guides because the guides wear oblong on opposite sides at both ends. A small Brush Research ball hone works way better.
 
Reamers dont get everything out of the guides because the guides wear oblong on opposite sides at both ends. A small Brush Research ball hone works way better.

I had seen your recommendation and thought of going that way. I also thought that the reamer would take the guide back to original ID specs and that the remaining carbon would act to take up any wear in the guides. I figured that I would be better with the guides at new specs if they were worn at all. Then again, if carbon has been building up for years, then the wear should be in the carbon and not the bronze, making it a moot point.

Your thoughts?

Larry
 
I had seen your recommendation and thought of going that way. I also thought that the reamer would take the guide back to original ID specs and that the remaining carbon would act to take up any wear in the guides. I figured that I would be better with the guides at new specs if they were worn at all. Then again, if carbon has been building up for years, then the wear should be in the carbon and not the bronze, making it a moot point.

Your thoughts?

Larry

My thought is you don't want any coked oil remaining in the guides. The ball hone adds a crosshatch which helps retain oil. Any of the guides I have cleaned up have never exhibited subsequent problems. Literally takes less than 10 seconds to clean up a guide with a ball hone.

The valve stem is loaded sideways from the rocker geometry, then you have the mechanical centering of the valve as it contacts the seat which straightens the valve. The valves stretch so the valves themselves get their stem diameters reduced over its life. So I'm not of the opinion that the clearances matter much because things start wearing day 1.

IMO dirty oil causes stuck valves. I haven't had any on my own airplanes in the last 10 years as I do not change oil on arbitrary times. Gets dirty (dark brown), I change it. On my last oil change it was 41 hours.
 
My thought is you don't want any coked oil remaining in the guides. The ball hone adds a crosshatch which helps retain oil. Any of the guides I have cleaned up have never exhibited subsequent problems. Literally takes less than 10 seconds to clean up a guide with a ball hone.

The valve stem is loaded sideways from the rocker geometry, then you have the mechanical centering of the valve as it contacts the seat which straightens the valve. The valves stretch so the valves themselves get their stem diameters reduced over its life. So I'm not of the opinion that the clearances matter much because things start wearing day 1.

IMO dirty oil causes stuck valves. I haven't had any on my own airplanes in the last 10 years as I do not change oil on arbitrary times. Gets dirty (dark brown), I change it. On my last oil change it was 41 hours.

Thanks for sharing!
 
Rocketbob - can u provide details of the brush size U recommend?? Not positive I have a sticking valve, yet. But not running as smooth as it used to. And getting into that 500+ hour territory. I do change oil between 30 and 40 hours.
 
valve check stuff

so I bought all this stuff for the a valve check plus Bobs' .5 inch dia hone but decided to go for another flight as a final look and record cylinder #1 CHT and EGT lag times. I thought I felt a slight miss for about 10 seconds after start and thought " uh-hum, yep", but the flight was perfect with all CHT and EGT responding normally. cylinder #1 was in-sync with the others. I guess I'll wait for the symptoms to re-appear before doing anything.

38 hours on the oil. it stays clean until 50 hr change.

I'll do a borescope and compression and spark plug check at the upcoming oil change.

IMG_20201030_202819.jpg


IMG_20201030_181737.jpg
 
I agree dirty oil is a large contributor to sticky valves, I change mine religiously at 25 hrs and do the filter every other change. Oil is cheap.
 
Ignition wiring, spark plug or connection? If one plug in cylinder #1 were misfiring, would not the symptoms be what you described? Slight drop in that cylinder's power (i.e., lower cht), but not enough to cause a noticeable roughness?
 
I use Marvel Mystery Oil when it's needed. It's somewhat of a family tradition. My grandfather said they had barrels of MMO for the B-25s he was flying out of Okinawa back in WWII. He had bullet holes, but no stuck valves.
 
Ignition wiring, spark plug or connection? If one plug in cylinder #1 were misfiring, would not the symptoms be what you described? Slight drop in that cylinder's power (i.e., lower cht), but not enough to cause a noticeable roughness?

another flight and no abnormal issues for cylinder #1. go figure. perhaps you were right that there was something with the ignition or something on a plug that was causing the issue. I'll borescope the cylinders on the next upcoming oil change and check the plugs ignition leads. so for now, at 850 hours I'm not going to do much else unless the borescope shows something.
 
another flight and no abnormal issues for cylinder #1. go figure. perhaps you were right that there was something with the ignition or something on a plug that was causing the issue. I'll borescope the cylinders on the next upcoming oil change and check the plugs ignition leads. so for now, at 850 hours I'm not going to do much else unless the borescope shows something.

On mine, I found corrosion in a few of the spark plug wire contacts (I have auto spark plugs, Lightspeed ignitions). The engine was running fine, but I'd hear an rpm clocked buzzing in the radio when breaking squelch. I cleaned the contacts up, and now keep them dressed with Tri-Flow. No more corrosion, no more noise.

I would expect the EGT to be higher, however, if one plug is misbehaving, the opposite of what you reported...
 
inspection report

oil change and inspection.

borescope inspection of suspect cylinder #1 - everything looked normal

compression check of cylinder #1 - 70 psi, this is a drop from previous inspection of 78 psi

spark plugs:
cylinder #1 top and bottom measured 2.6K ohms
all other spark plugs for all cylinders measured 1.3K - 1.6K ohms

the spark plug check was the interesting note. I don't understand why cylinder #1 plugs would be different but they were. a cause or a symptom?
 
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oil change and inspection.

borescope inspection of suspect cylinder #1 - everything looked normal

compression check of cylinder #1 - 70 psi, this is a drop from previous inspection of 78 psi

spark plugs:
cylinder #1 top and bottom measured 2.6K ohms
all other spark plugs for all cylinders measured 1.3K - 1.6K ohms

the spark plug check was the interesting note. I don't understand why cylinder #1 plugs would be different but they were. a cause or a symptom?

2.6 is out of spec, but not sure it is enough to cause problems. As mentioned earlier, when one plug doesn't fire, you should expect to see the EGT rise a good bit (100) on that cylinder. I also doubt that a drop in compression to 70 would cause a noticeable change in CHT or EGT. I recently had a broken top compression ring (50/80) and after a cylinder replacement, I got pretty much the same CHTs and EGTs on that jug as before.

Larry
 
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At 70/80, down from 78, did you notice more hiss at the oil filler (rings), exhaust pipe (exhaust valve) or air inlet (intake valve)?

Plugs that ohm infinite still fire, they just beat up your mags.

Twice the motor has said it is not happy.
 
At 70/80, down from 78, did you notice more hiss at the oil filler (rings), exhaust pipe (exhaust valve) or air inlet (intake valve)?

Plugs that ohm infinite still fire, they just beat up your mags.

Twice the motor has said it is not happy.

the plugs are all within spec but cylinder #1 resistance for both plugs was slightly higher for some reason. I could only listen to the oil fill port since I was only one and it sounded like it was leaking there. all CHT and EGT are responding evenly and normally. it still climbs out at 2000 FPM. I'll keep an eye on it. someone said "oil is cheap". I think I will reduce my oil change maintenance interval.
 
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Have you ever found the problem? We did ball hone the guide 200h ago, now we are starting to see the beginning of a burnt valve. I have no idea if it is related, as we have had the exact symptoms of a late waking-up of cylinder #1. It is also the one that leans the first.

Let us know,
EL
 
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