Broken spark plug - 16v engine
Captain Obvious
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Joined: Aug 2003
Posts: 22,846
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From: Cambridge, Ontario, Canada
I use anti-seize on my spark plugs, wheel Lug nuts/bolts, etc. My rationale is that the torque spec is derived from trying to achieve the correct amount of thread stretch on the plug, fastener, or properly crush a dealing washer, etc. I don't think stiction of the dry threads on each other factors into the correct torque spec, and installing fasteners or plugs dry might actually result in not tightening a fastener enough. Creating a barrier that prevents rust or helps air or liquid from migrating through the threads is just an added bonus.
RL Community Team
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Joined: Oct 2007
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From: Clemson, SC
I've been using anti-seize on my spark plug threads for about 40 years (as far back as when I had a 50cc motorcycle in grade school) and can't recall ever having a spark plug not want to come out or stripping a plug hole where it had to be helicoiled, chased, or repaired, so I may very well be over-tightening them a few ft.lbs., but I'm not likely to change a process that has worked flawlessly for this many years on literally hundreds of spark plugs.
The other advantage to to the anti-seize is that it can trap tiny particles of dirt or debris instead of those falling down into the combustion chamber. In-fact, it's a useful trick to use it if you have to chase the threads on a plug hole to put some anti-seize on the tap so that any metal shavings freed by the tap stick into the voids of the tap rather than dropping into the cylinder head, which I'm sure leaves some anti-seize on those threads in the head when you go to install the spark plug.
Burning Brakes
Joined: May 2016
Posts: 840
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From: Nazareth, PA
Nice work! I have learned that sometimes I have to step away from a problem, come back fresh, and often I will figure out a problem in a matter of minutes.
I have read that torque should be reduced by 30% when using anti seize. If you hand tighten the plug and tighten by angle (I think a half turn) then the torque is not a factor.
I have read that torque should be reduced by 30% when using anti seize. If you hand tighten the plug and tighten by angle (I think a half turn) then the torque is not a factor.
Nordschleife Master
Joined: Apr 2003
Posts: 9,601
Likes: 39
From: Abbotsford B.C.
If the plug is silver in color it is factory zinc played and you should not use loctite.
If the plug is black in color it has no factory coating and should be installed with a silver color anti-seize in aluminum heads. Use copper anti-seize if installing in iron heads.
If the plug is black in color it has no factory coating and should be installed with a silver color anti-seize in aluminum heads. Use copper anti-seize if installing in iron heads.
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Joined: Nov 2006
Posts: 14,898
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From: Pittsburgh, PA
man you guys are pikers. I also have modern Mustangs, with the famed 4.6 litre, 3 valve motor. The original plugs used by Ford were 2 part plugs, and are notorious for breaking upon removal. I once broke 4 out of 8 in a change (always change to the upgraded, one piece plug). The issue is so bad, Ford issued a TSB with detailed instructions on it, and there are numerous threads on the Mustang forums about it too. There is even a special tool to remove the broken part of the plug - called the Lisle tool. Nothing tightens a sphincter like removing plugs from a block when you KNOW some of them will break apart in the block.
Captain Obvious
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Joined: Aug 2003
Posts: 22,846
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From: Cambridge, Ontario, Canada
OK, that's good info, but does that dry torque spec from when the engine is built with all pristine parts also take into account combustion debris (like carbon) getting into the threads, galvanic action between dissimilar metals of the plug threads reacting with the head material in the head threads, rust like we saw on this stuck plug, a tiny bit of dirt that might get into the threads from around the plug seat when it's loosened, etc?
I've been using anti-seize on my spark plug threads for about 40 years (as far back as when I had a 50cc motorcycle in grade school) and can't recall ever having a spark plug not want to come out or stripping a plug hole where it had to be helicoiled, chased, or repaired, so I may very well be over-tightening them a few ft.lbs., but I'm not likely to change a process that has worked flawlessly for this many years on literally hundreds of spark plugs.
The other advantage to to the anti-seize is that it can trap tiny particles of dirt or debris instead of those falling down into the combustion chamber. In-fact, it's a useful trick to use it if you have to chase the threads on a plug hole to put some anti-seize on the tap so that any metal shavings freed by the tap stick into the voids of the tap rather than dropping into the cylinder head, which I'm sure leaves some anti-seize on those threads in the head when you go to install the spark plug.
I've been using anti-seize on my spark plug threads for about 40 years (as far back as when I had a 50cc motorcycle in grade school) and can't recall ever having a spark plug not want to come out or stripping a plug hole where it had to be helicoiled, chased, or repaired, so I may very well be over-tightening them a few ft.lbs., but I'm not likely to change a process that has worked flawlessly for this many years on literally hundreds of spark plugs.
The other advantage to to the anti-seize is that it can trap tiny particles of dirt or debris instead of those falling down into the combustion chamber. In-fact, it's a useful trick to use it if you have to chase the threads on a plug hole to put some anti-seize on the tap so that any metal shavings freed by the tap stick into the voids of the tap rather than dropping into the cylinder head, which I'm sure leaves some anti-seize on those threads in the head when you go to install the spark plug.
Rennlist Member
Joined: Mar 2007
Posts: 3,670
Likes: 76
From: Central Virginia
If the plug is silver in color it is factory zinc played and you should not use loctite.
If the plug is black in color it has no factory coating and should be installed with a silver color anti-seize in aluminum heads. Use copper anti-seize if installing in iron heads.
If the plug is black in color it has no factory coating and should be installed with a silver color anti-seize in aluminum heads. Use copper anti-seize if installing in iron heads.
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Instructor
Joined: Oct 2003
Posts: 117
Likes: 4
From: Winnipeg, MB
I've always used anti seize on plugs, lug nuts, etc. I've never had an issue pulling a plug or lug nut in 40 years of working on cars but have had plenty of issues releasing plugs, lug nuts, etc on cars I've purchased that didn't have anti seize, so I lean towards using the anti seize versus not.
Not sure if this is the correct approach but it does seem to work.
Not sure if this is the correct approach but it does seem to work.