Spark plug gaskets - replace or not?

Dan Thomas said:
Champion says not to use any graphite-based anti-seize, then they sell you a graphite-based anti-seize. I have used Nevr-Seize, which has aluminum and graphite in it, and Copper-Coat which has copper and graphite. Keep any of thise away from the business end; it can melt and run onto the electrodes and short them.

I would never use RTV. It crumbles when the plug is removed and can foul the top ring in its groove. RTV anywhere on an aircraft engine is asking for trouble. It doesn't show up in Lycoming's or Continental's approved sealants lists.
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RTV 102 is an approved sealant for crankcase parting flanges per Lycoming SI 1125D.

Also, copper based anti-seize is the preferred Lycoming choice per SI 1042AH, also says always use new spark plug gaskets.
 
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Look at a spark plug, you will notice that the shoulder of the plug is not a 90 degree angle.
Flipping the seal over will force the seal to re-form the copper seal.
Annealing is a waste of time.
 
bnt83 said:
RTV 102 is an approved sealant for crankcase parting flanges per Lycoming SI 1125D.

Way different than a spark plug.

Also, copper based anti-seize is the preferred Lycoming choice per SI 1042AH, also says always use new spark plug gaskets.
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the nickel anti-seize is better, copper has a much lower temp range than nickel. Read the can .
 
Salty said:
Another gem from Tom's vault. I'm not even going to ask though.
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Ask your self, how much is your time worth? your going to throw the seal away after 5 times.
 
I figure at 36 cents apiece, it is quite possibly the cheapest item to buy on an aircraft even if you have to buy 8-24 of them.
 
Gaskets are such a low cost item I always replace them with new ones. I also carry a spare plug with a fresh gasket and appropriate tools with me. Doesn't add much weight and makes it easy to deal with a fouled plug when traveling (though good leaning practices pretty much eliminate that occurrence).
 
Matthew Rogers said:
I just changed my plugs for the first time ever and intentionally read the instructions because.....that is what they are for. If I followed them, I did it correctly. If someone else does it a different way, it may be an alternative correct way...or not. Sometimes there are more than one correct way.
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Yup, that would be the thing to do. But I was not installing new plugs, just re-installing the old ones after borescoping my cylinders. So I came here for answers.
 
SkylaneKY said:
So I came here for answers.
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No shortage of those...
FWIW...
The FAA 43.13-1B "Acceptable Methods" sez: "NOTE: Never install a spark plug which has been dropped and always use new gaskets every time you install a spark plug. " and "Apply anti-seize compound spar-ingly to the shell threads, but do not allow the compound to contact the electrodes since the material is conductive and will short out the plug."
But, obviously, actual practice depends on the practitioner.
 
Capt. Geoffrey Thorpe said:
No shortage of those...
FWIW...
The FAA 43.13-1B "Acceptable Methods" sez: "NOTE: Never install a spark plug which has been dropped and always use new gaskets every time you install a spark plug. " and "Apply anti-seize compound spar-ingly to the shell threads, but do not allow the compound to contact the electrodes since the material is conductive and will short out the plug."
But, obviously, actual practice depends on the practitioner.
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I did this verbatim. The only question is does the flat side of the gasket go on the spark plug side, the cylinder side, or it's not the end of the world either way?
 
When I was young and cheap, and did of my own routine maintenance, I annealed copper gaskets and re-used them. If you had a couple of sets you could rotate them, or always find another one to install if you dropped one and lost it. But they are so cheap compared to anything else you do with and airplane, you might as well install new.
 
Dan Thomas said:
It isn't flat because the washer is punched out of copper flat sheet. That leaves the punch side flat and die side convex.
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^^^^^This^^^^^

I'll vote for the flat side toward the head because the head is soft aluminum and flat. The steel plug can deform the copper washer to fit.
 
flyingbrit said:
^^^^^This^^^^^

I'll vote for the flat side toward the head because the head is soft aluminum and flat. The steel plug can deform the copper washer to fit.
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Some engines have a steel insert for the plugs and it has a flat gasket surface. The copper is softer than the aluminum in any case as long as it's new or annealed. It work-hardens when it's crushed, making it less likely to seal a second or third time. It really doesn't matter which side of a new gasket goes against the head.
 
Dan Thomas said:
Some engines have a steel insert for the plugs and it has a flat gasket surface. The copper is softer than the aluminum in any case as long as it's new or annealed. It work-hardens when it's crushed, making it less likely to seal a second or third time. It really doesn't matter which side of a new gasket goes against the head.
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This is the answer I'm hoping for.
 
flyingbrit said:
^^^^^This^^^^^

I'll vote for the flat side toward the head because the head is soft aluminum and flat. The steel plug can deform the copper washer to fit.
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It's telling that the 27-page Champion spark plug manual doesn't specify gasket orientation at all. I've heard flat side toward spark plug flange, convex toward cylinder head...but next time I'll alternate for each plug. :D
 
How about this.. does anyone have a new plug from champion or tempest? Which way does the manufacturer put the washer on from the factory? If I remember correctly with new tempests the flat side of the wash is facing the engine. Can anybody confirm this on a new plug?

Thanks
 
The a&p I work with recently admonished me to put the flat side toward the plug, for whatever that's worth. He has shown himself to be a meticulous mechanic. Personally, I don't see what difference it would make...copper is soft, and it's gonna get crushed to the right sealing shape regardless if it's new. However, I will do ss my respected A&P advises until I'm smarter and more experienced than he is. That'll be a LONG time comin'....
 
Dan Thomas said:
Champion says not to use any graphite-based anti-seize, then they sell you a graphite-based anti-seize. I have used Nevr-Seize, which has aluminum and graphite in it, and Copper-Coat which has copper and graphite. Keep any of thise away from the business end; it can melt and run onto the electrodes and short them.

I would never use RTV. It crumbles when the plug is removed and can foul the top ring in its groove. RTV anywhere on an aircraft engine is asking for trouble. It doesn't show up in Lycoming's or Continental's approved sealants lists.

A good plug washer prevents the escape of any gases past it. Those gases carry crud that contaminate the threads and make the plug hard to remove and can erode the head.
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LIfe is simple because I could not care less if you ever use RTV. I have used it in many places with great success for about 40 years and never a problem and will continue to do so. Actual experience trumps an opinion.
 
iflyatiger said:
How about this.. does anyone have a new plug from champion or tempest? Which way does the manufacturer put the washer on from the factory? If I remember correctly with new tempests the flat side of the wash is facing the engine. Can anybody confirm this on a new plug?

Thanks
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Here’s a new Tempest, appears to be packaged flat side toward plug
 

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Snowmass said:
LIfe is simple because I could not care less if you ever use RTV. I have used it in many places with great success for about 40 years and never a problem and will continue to do so. Actual experience trumps an opinion.
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There are a lot of practices outside the approved standard practices that can work OK for a long time, until one day they don't. An example is the unapproved method of lockwiring turnbuckles using lockwire twister pliers and curling the cut end over into a loop that can someday snag on something and suddenly the control doesn't move properly. Or the nylon zip ties used to secure cables and wiring to an engine mount, until the grit that gets under the tie eats into the mount tubing and requires a major engine mount repair. My experience has covered both of these along with many others. AC43.13 was written in blood.

Repetition of a mistake never makes it right. Or safe.
 
True, but remember our engines are 1935 technology. If you want modern approach look to the modern, high tech auto engines which use lots of RTV. As an aero engineer my raison d'etere is find better ways of doing things.
 
Snowmass said:
True, but remember our engines are 1935 technology. If you want modern approach look to the modern, high tech auto engines which use lots of RTV. As an aero engineer my raison d'etere is find better ways of doing things.
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It's not just blanket,one-size-fits-all "rtv" in today's auto engines. As the owner of a Scion FRS (joint project between Toyota and Subaru, designed by Toyota but built by Subaru using a Subaru engine... Also known as a Subaru BRZ and now that Scion is gone, a Toyota 86) who was fortunate enough to have the techs at Toyota use the wrong type of sealant and over apply it during some warranty and recall work, I now have a new engine in the car because they wrecked the original engine with "RTV." Had they read the expressly clear procedures detailed in the Subaru service bulletins addressing the procedures performed and actually followed them, all would have been well.
Dabbing RTV on spark plugs threads is not wise.

Oh..and it's "raison d'etre"... Literally, "reason for to be." Not sure what "raisin d'etere" is... Close to "reason for shelving," but not quite...
 
Snowmass said:
True, but remember our engines are 1935 technology. If you want modern approach look to the modern, high tech auto engines which use lots of RTV. As an aero engineer my raison d'etere is find better ways of doing things.
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At your own risk, then. Don't preach it to others. An "aero engineer," even if you asre such a thing, is not the same as a trained and experienced aircraft mechanic.
 
RTV on spark plug threads is the same as putting teflon tape on the threads of flare fittings. A fundamental misunderstanding of the basic principles.
 
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Snowmass said:
I will only now use fine wire plugs and I never replace nor anneal the copper washers BUT I always put hi-temp RTV on the plug threads. The RTV stops exhaust gasses getting past the first thread of the plugs. In many thousands of hours I have had NO plug problems. One test is worth a thousand opinions.
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That’s a really bad idea.
 
MooneyDriver78 said:
And this is why I would never buy an experimental.Tom
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Not everyone that owns an experimental is confused ...

(No I don't use RTV om my plugs or my gaskets. I do use it on my baffling ...)
 
Daleandee said:
Not everyone that owns an experimental is confused ...

(No I don't use RTV om my plugs or my gaskets. I do use it on my baffling ...)
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The problem is you won’t know. You’re buying from a total stranger who built the plane in his garage. A prebuy won’t catch the errors. At least certified planes and mechanics have approved procedures they follow.
 
Snowmass said:
LIfe is simple because I could not care less if you ever use RTV. I have used it in many places with great success for about 40 years and never a problem and will continue to do so. Actual experience trumps an opinion.
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I have an alcoholic neighbor who's driven drunk every day in the 25+ years I've lived next to him. He's never gotten a DUI and never been in an accident. My opinion is people shouldn't drive drunk, but I suppose his experience trumps my opinion.
 
MooneyDriver78 said:
The problem is you won’t know. You’re buying from a total stranger who built the plane in his garage. A prebuy won’t catch the errors. At least certified planes and mechanics have approved procedures they follow.
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Nope ... I built mine. Again, not all experimental owners are confused.

BTW ... I’m not a believer that because it’s a certified aircraft that nothing erroneous was ever done to it. Even on certified planes there are times when the rules aren’t followed. To that point I’m sure we can agree ...
 
Matthew Rogers said:
Tempest plug instructions make absolutely no mention about there being a “correct” orientation for spark plug gaskets. If they don’t even mention it in their spark plug installation guide at all in any manner, it can’t be anything more than an old wives tale.
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Regardless of what Tempest does, the FAA addresses it and flat side toward the plug is the *only* approved way to do it.

bnt83 said:
There would be some upset owners if a mech required replacement of the spark plug gaskets at every R&R that position would surely apply to spark plug gasket CHT probes too.
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The rings on a CHT sensor are harder and less likely to deform, and it's just one potential bad seal out of 8 on a 4 cylinder engine. That said if it were cost effective to replace them they probably would. A larger issue is that CHT numbers in most flight manuals are based on bayonet probes, not spark plug ring probes and the latter usually read 25-50 degrees high.

I don't know why owners would be upset if a mechanic required new gaskets ever time a spark plug was removed or replaced. Spark plug gaskets are cheap. I buy them by the 100 pack for about $30.00. That's $0.60 per cylinder, a total of $2.40 every 50 hours, or $0.048 per tach hour, and probably down around $0.04 per flight hour. I'd be more upset if a mechanic wasn't following approved practices. What else is he cutting corners on?

SkylaneKY said:
I did this verbatim. The only question is does the flat side of the gasket go on the spark plug side, the cylinder side, or it's not the end of the world either way?
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My understanding is that when the flat (sharp edged) side is placed against the aluminum cylinder head it can start to cut into the head, which creates a stress riser. Is that a big deal? Maybe, maybe not. But since:
- cylinders are expensive;
- spark plug gaskets are cheap;
- the FAA approved and *requirted* method is flat side toward the plug; and
- it's just as easy to do it the right was as it is to do it the wrong way;

why is there even a question about what side faces the cylinder?
 
MooneyDriver78 said:
And this is why I would never buy an experimental.


Tom
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Being certified in no way insures you'll never discover substandard repairs which were performed by non-certified individuals and then went through years of annuals undetected. When I was growing up my family owned and ran two small businesses. A hardware store and an auto parts store. I worked in both for many years. In that time, I helped quite a few customers who were looking for stuff they were going to use to fix or modify their certified airplanes.
 
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