stout

The good news: Someone good should be able to get that out, and possibly without pulling the cylinder head.

I remember the "snap" of something arguably harder to get out of a cylinder head when I was in high school and didn't know much about "feel" when using a wrench: an exhaust stud. A steel stud in an aluminum head, and (much) smaller diameter than a spark plug to boot. My father, an engineer, applied plenty of Kroil > tapping > Kroil > tapping > Kroil > tapping > etc and then eventually an "easy out" to no avail—the easy out broke off in the stud, so it was hardened steel inside of a steel stud inside of an aluminum head. A shop in Berkeley was able to extract the stud and repaired the head to accept a new stud with a helicoil, all with the engine still in the car. It wasn't cheap, but it was worth it: Despite my father's misgivings with a helicoil, I never had an issue with that fix for more than 20~ years, and only replaced the engine because I was after more performance.

I have no idea whether the above will transfer to a 991.2, but you're dealing with valuable enough parts that I'd be ready to have the engine pulled if a technician wants to get better access and/or leverage. Whatever the cost, you'll be ahead in the long run whether you're keeping the car (my vote!) or moving it on. As others have noted: Too cool on the car's mileage, and I'd love to know how it's been other than this. I'm at 44,000 miles, and my 991.2 Carrera still wows me all the time…

BSO

Just had the plugs on my '19 C4S at 4 years/20k no issues. It was as stated not cheap. Had a plug seize in one of my motorcycle engines and the thread stripped on removal, in went a helicoil. Was never happy knowing that the head was damaged, but the engine ran fine,

It's bad enough that your plugs snapped off, just hope the threads survive the extraction. Whoever does it needs to heat the area and liberally use penetrating oil before attempting the removal.

Good luck.

blackcheetah

Sorry to ear about your nightmare i have the 2 head available in case you need it

Bxstr

Keep us posted on the resolution, but good reminder for all of us to change based on time or mileage. Guessing this was caused more by mileage than by time since a 991.2 would be a 2017+ and they were already changed once.

911T4ME

My checks show 3 years or 30k miles for 991.2.

dannyss

Your situation is convincing me I should change them this next summer. The 4 year period is approaching for my 2019 C4S.
Good luck and let us know the solution.

RennListUser01

Hi All,

This is a terrible thing to have happen during DIY - are there data on occurrence at dealers or independent shops?

So, if this were a Toyota forum, would someone note they usually squirted PB Blaster on the day prior attempting to remove JIC?

Other DIY sites mention changing with engine hot if one is concerned?

Other DIY sites noted the use of hot engine, some product like PB Blaster, and using an impact wrench on very low setting - impacts supposedly better than massive torque ...

NGK link ... btw, other bits from NGK say they have special plating that helps prevent getting stuck - link recommends 30% reduction in torque if using anti-seize. https://www.ngk.com/ngk-plug-torque-settings Does Bosch mention having a visiting like this?

Based on the net horribleness of this scenario, I'm going to carefully apply a tiny bit of anti seize when I do my plugs ... apparently this is common on the F cars.

Video on using standard extraction tool - application is always a function of where the shear occurred ... and what can be inserted into the center of what remains of the plug ... the photo seems to indicate that the shear occurred a few threads down?
Another video - shows the porcelain component still attached that has broken off in OP's photo? Saw another video that has a device that crushes the porcelain so an extractor can be used.

Tommy L Garage

Sorry to hear that. Having said that, how handy are you?
If there is access, spray PB blaster in there and drill a small hole through the center of the plug. Don’t go through. Then use an extractor bit and hopefully that will work. Can’t see any other way to do it without removing the head.

MingusDew

HardRider

Bewildering why everyone keeps interating the change interval. How does that help remove the broken plug? I pretty sure a local Porsche shop/mechanic has seen this before and can remove. Easy enough to get an extractor in the broken plug, I imagine with the right amount of heat it will come right out. Oh yea you should change them more frequent.....

RennListUser01

And, a bit of anti-seize ... if one reduces the installation torque a bit?

Revsportz

Props for having 142k miles on the 991.2

DC911S

I agree, a slight amount of anti seize will not drastically alter the torque setting. One could do an experiment where you use the proper torque wrench to install a plug. Place some sort of mark on the cylinder head cover where it’s hitting afyer x turns and hitting the right value. Then take it back out, apply some compound and do it again, noting the difference between the marks.

rensoyka

I've broken plugs before when trying to remove them but never sheared one off at the threads. personally I'm thinking the head needs to come off. I'd be worried about debris getting into the cylinder from jamming an extractor in there.

RennListUser01

Pretty easy to keep it clean while removing, and lots of suction from a specialty vacuum would be appropriate ... then scope it to see what's in there?

Head removal seems a bit extreme (does engine need to come out?) ... this can't have been the first time this has happened.