Has anyone ever seen a spark plug fail like this and possibly know why it did? This is on a Volvo that I did a head gasket job on where #1 and #2 original spark plugs were seized in the head during removal. We sent it to the machine shop to get it faced and asked them to remove the plug and put in a helicoil. They did that and after putting it all back together the car ran great around town. So I went on an extended test drive prior to shipping to the customer and during the drive while going up a big hill the car starting misfiring real bad. I got it towed back to the shop and looked into and found this. The helicoil came out with the plug and it looks like the tip of the plug melted and deformed itself. There doesn't appear to be damage to the top of the pistons or the valves. Just wondering why this would happen [2007 Volvo C70 T5, Engine/Propulsion Photo] [2007 Volvo C70 T5, Engine/Propulsion Photo]

Martin Calvillo
Technician
A+ Auto
Poway, California, USA

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