Broken facet on a spark plug | Page 2 | Ford Explorer Forums - Serious Explorations

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Broken facet on a spark plug

Could you determine where the resistance was from that caused the hex to round? Once you embedded the socket on the plug, did it take much effort to unscrew it?

Both the threads and the ground barrel look pretty clean. From the picture, there is no evidence as to why you might have had that problem.

I picked up this set that you posted, just in case. Don't really know how good they work but I sure I will get an opportunity with something or other.

I think initially the spark plug was defected. Because when I tried to unscrew it first time with 9/16 socket, I didn’t apply much effort and the hex got rounded.
At this time I removed it with 13mm socket on a hot engine and a bit of carb cleaner, didn’t need to apply much force. It looks clean because it lasted 50000 km, but recently there have been misfire on 8th cylinder, so after I changed it, the misfire got away and the engine runs perfect, so this spark plug lasted only 50000km.