Spark plug gaskets - replace or not?

Katamarino

Katamarino

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Katamarino
Whenever I clean, gap and rotate my plugs in the US my A&P uses new copper gaskets when we put the plugs back in.

When I did a spark plug service in the UK, they didn't have any gaskets and said that they never replace them, they re-use the existing ones for the life of the plug.

What do the assembled masses think; change, or don't change? If it's OK not to change, then I won't bother buying and hauling around a bunch of copper gaskets.
 
Cu washers crush when the plugs/bolts are tightened. They're a one use item for me, but I'm not an A&P, and didn't sleep at Holiday Inn Express last night.
 
Hate to get all practical, but has there ever been an incident, or SDR issued, for a problem when someone reused one of these?
 
As little as they cost why not just replace them. Order enough to change them 2-3 times and just rotate your inventory. That way, if your shop doesn’t have any then you hand them your stock and order replacements whenever you get a chance. Any crush washer is designed as a 1 time use since they form to that specific orientation and location. Playing devil’s advocate but would you really want to be “that guy” for a spark plug gasket/washer?


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How do spark plug CHT sensors fit into the equation? Do they need to be annealed each time?
 
I just bought a 100-pack of copper washers from ACS for about $30. That works out to about $2.50 for every 100 hours when I clean and re-gap the plugs, typically about once a year. Just bought some Tempest plugs, and they came with the washers....can't remember if the Champions did originally.

I don't think they're technically crush washers, but the soft-ish copper does squish a bit when torqued, making a better seal over tiny imperfections. And remember to put the flat side toward the plug, and the rounded side toward the cylinder head.
 
I always replace them and throw the used ones in a can. Once a year or so I anneal them and recycle them back into the hangar tool chest.

Let'sgoflying! said:
Hate to get all practical, but has there ever been an incident, or SDR issued, for a problem when someone reused one of these?
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They are sealing against pulsating high pressure. They cost less than any other aviation part I can think of. Why wouldn't you replace them? Especially when the used ones can be retreated and reused for virtually no cost.

If you get a leak past the plug gasket on the head side, it'll be a few AMUs to repair it.
 
GRG55 said:
I always replace them and throw the used ones in a can. Once a year or so I anneal them and recycle them back into the hangar tool chest.



They are sealing against pulsating high pressure. They cost less than any other aviation part I can think of. Why wouldn't you replace them? Especially when the used ones can be retreated and reused for virtually no cost.

If you get a leak past the plug gasket on the head side, it'll be a few AMUs to repair it.
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You seem to be considering reusing annealed gaskets as “replacing” them, but I don’t think that it what everyone else means.

I’m not sure anyone was suggesting reusing gaskets without annealing them first.
 
Well they are "gaskets" so, are there any other gaskets on your engine that you'd consider re-using? True, you can inspect them and anneal them and re-use them but mostly we just put new ones on. They look nice when they're new.
 
Salty said:
You seem to be considering reusing annealed gaskets as “replacing” them, but I don’t think that it what everyone else means.

I’m not sure anyone was suggesting reusing gaskets without annealing them first.
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Well actually I replace mine from a large box of new ones I bought from Spruce some time ago. I haven't had to dip into the annealed ones yet, but my cheap-azz hangar partner and his friends raid them and throw their used ones in my can.
 
@Katamarino - Is the spirit of your question for maintenance at your hangar, or for your around the world trip?

It's a low $$ item, and probably a small weight addition, but all those little weights add up.
 
Ravioli said:
@Katamarino - Is the spirit of your question for maintenance at your hangar, or for your around the world trip?

It's a low $$ item, and probably a small weight addition, but all those little weights add up.
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It's to have with me round the world. I was surprised when they didn't have any in the UK as I had always thought it was an automatic item to replace when doing plugs!

I'll just eat less ice cream to make up for the weight...
 
I'd take a set with me, never can tell when one goes missing. new plugs yes, new gaskets.
 
Katamarino said:
I was surprised when they didn't have any in the UK as I had always thought it was an automatic item to replace when doing plugs
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Hmm, makes one wonder if they’ve learned something about not needing to change these so often, that we don’t yet know yet.
Maybe they just haven’t had the constant cylinder failure that we’ve had when people refuse to do so :dunno:
 
Walboy said:
Why? What is the technical reason?
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Depends on the type of gasket. If solid copper type it doesn't matter. On the layered steel version the larger flat side is recommended to be on the plug side to offer a better "bearing" face and acts like a washer to the smaller diameter side which seals at the cylinder head surface. At least that what was a old Auburn plug tech rep explained years ago.
 
Everybody else says just the opposite, that the flat side goes against the spark plug and the concave side goes against the cylinder head.
 
Let'sgoflying! said:
Hate to get all practical, but has there ever been an incident, or SDR issued, for a problem when someone reused one of these?
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I'm not aware of any.

I do know a club where they reanneal the washers and reuse them. They've flown probably over a quarter million hours over the years across multiple airplanes without any issues due to reusing washers. That's not proof, it just 250,000 anecdotal stories.
 
SkylaneKY said:
Everybody else says just the opposite, that the flat side goes against the spark plug and the concave side goes against the cylinder head.
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There is NO concave side. One side is pretty durn near flat. The other has a slight radius (convex if you like) to it.
Flat side to the plug.
 
wilkersk said:
If you need to reuse them, just anneal them with a propane torch. Heat 'em till they glow orange all the way around. Then, dunk 'em in a cup of water. Make sure the concave surface goes toward the plug. People have been doing this for years.

https://video.eaa.org/detail/video/57437956001/annealing-spark-plug-gaskets
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Everybody else says just the opposite. Flat side toward the spark plug and concave side toward the cylinder head. Since your message is the one I saw - all of mine are in upside down
 
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.
 
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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I would love to believe that’s true since mine are all in upside down
 
SkylaneKY said:
I would love to believe that’s true since mine are all in upside down
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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.
 
the reason that a spark plug isn't flat, is so you can turn the seal over and make it re-form the seal.
plugs only last 500 hours, when you clean and re-gap then every 50 hours, they get trowed away before you need to anneal them.
 
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.
 
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.
 
I also wire brushed the plug thread OD's and cylinder thread ID's to clean everything up before reassembling (with anti-seize of course). I felt it helped save the Helicoil inserts. Anyone else do that? or ?
 
nrpetersen said:
I also wire brushed the plug thread OD's and cylinder thread ID's to clean everything up before reassembling (with anti-seize of course). I felt it helped save the Helicoil inserts. Anyone else do that? or ?
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Ah...another can of worms. Which anti-seize do you use, copper, moly, or that black liquid stuff? And how do you wire brush the thread ID's keeping the crap out of the cylinder?
 
Tom-D said:
the reason that a spark plug isn't flat, is so you can turn the seal over and make it re-form the seal.
plugs only last 500 hours, when you clean and re-gap then every 50 hours, they get trowed away before you need to anneal them.
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It isn't flat because the washer is punched out of copper flat sheet. That leaves the punch side flat and die side convex.

Ans yes, I have plenty of experience running many machines including massive punches.
 
Timbeck2 said:
Ah...another can of worms. Which anti-seize do you use, copper, moly, or that black liquid stuff? And how do you wire brush the thread ID's keeping the crap out of the cylinder?
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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.
 
Which camp are you in Dan, flat side towards the plug or the cylinder head?
 
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