Spark plug torque spec?

[Eric Arroyo]

My Googling skills have failed me. I can't seem to find the spec anywhere besides a couple posts saying "about 20ft/lbs" or "I used my arm calibrated torque wrench" (lol). I also saw the entire service manual posted, but the link has been taken down recently.

Does anyone know what the official spec is? I don't want to be that guy that over-torqued and broke something, or under-torqued and had the plug back its way out over the next 1000 miles haha. I used to just tighten them by feeling, but on a car this expensive, I'd rather do it right the first time.

 

[ZyroXZ2]

I've always followed the rule of hand-tight followed by 90 degrees by a wrench. Since these require indirect torque via u-joints, I've found I have to exert quite a bit more force (thanks to physics since I'm torque-ing via two bent u-joints) to achieve turning the extension/socket connected to the sparkplug a full 90 degrees after having hand tightened them.

Though that does not contain your specified number value, spark plugs are never very tight. They also won't "back out" because they're being pressed down by the coils/coil wire (which is also spring loaded, btw). People saying 20 ft-lbs are pretty accurate, though. Just make sure they're snug and you'll be fine.

 

[oddball]

No, spark plugs most certainly will back out. I had that happen on my '02 Lincoln LS with COPs. Engine still ran pretty good, but the spark plug was pogoing under the coil, which was held down by a cover. Smashed the top couple of threads in the head. Nothing some time, grease, and a tap couldn't fix in a parking lot.

Anyway, there are two types of spark plugs. Most have a flat seat with a crush gasket, some use a taper seat with no gasket. The taper seat ones are more sensitive and you should follow the manufacturer's procedure, whatever it is.
Ours uses crush gaskets. You can feel the gasket crush as you tighten down. Once it's crushed all the way, give the wrench another pull to 20-25 ftlbs. Use a 3/8" ratchet if you're worried about gorilla-handling it.
Put a dab of copper anti-sieze on the spark plug before installing. That'll make removal much easier.
If you use dielectric grease (totally optional), just rub a SMALL amount on the CERAMIC RIBS of the spark plug. Dielectric is an insulator, so you don't want any on the metal nubbin. The grease is meant to be used around the ribs, where the boot seals on the plug, to prevent any water or gunk crawling up in there and corroding the plug/spring. Yeah, most modern COPs just use a dinky little spring to connect the coil to the plug.

 

[RLittle]

No, spark plugs most certainly will back out. I had that happen on my '02 Lincoln LS with COPs. Engine still ran pretty good, but the spark plug was pogoing under the coil, which was held down by a cover. Smashed the top couple of threads in the head. Nothing some time, grease, and a tap couldn't fix in a parking lot.

Anyway, there are two types of spark plugs. Most have a flat seat with a crush gasket, some use a taper seat with no gasket. The taper seat ones are more sensitive and you should follow the manufacturer's procedure, whatever it is.
Ours uses crush gaskets. You can feel the gasket crush as you tighten down. Once it's crushed all the way, give the wrench another pull to 20-25 ftlbs. Use a 3/8" ratchet if you're worried about gorilla-handling it.
Put a dab of copper anti-sieze on the spark plug before installing. That'll make removal much easier.
If you use dielectric grease (totally optional), just rub a SMALL amount on the CERAMIC RIBS of the spark plug. Dielectric is an insulator, so you don't want any on the metal nubbin. The grease is meant to be used around the ribs, where the boot seals on the plug, to prevent any water or gunk crawling up in there and corroding the plug/spring. Yeah, most modern COPs just use a dinky little spring to connect the coil to the plug.

correct!

If a plug has a gasket the 90 degree turn thing works.

Without a gasket turn till it stops and snug it.

 

[ScottyDangles]

19.6 - 29.4NM per Kia service manual. Coil pack nut 11NM.