15mm spark plug?

[Beacon]

So, I decided to change my spark plugs today and now I have some questions.
1) did GM make a spark plug that needs a 15mm socket?

Plug 2 is an ACDelco 3 thru 6 are Denso. Plug 2 fits a 12 point 15mm socket very well and 3-6 fit a 5/8 well. I was not able to remove plug 1, it seems like the socket is either spinning around the plug or is not completely seating on it, and I believe I just got lucky that #2 came out.
The 1st pic shows the boots from left to right 3, 2, 1
Plug 2 was very rusty for a spark plug, even the threads. I thought from reading previous threads that cylinders 5 and 6 were the ones that had the potential to collect water? Did I read that wrong?
I was not currently having any issues with the performance of the vehicle.

I only changed the plugs because I thought they were original, and the vehicle now has 97k miles.
FWIW 5 and 6 seemed to be very worn down, and #2 still seemed half decent.
I didn't have a 6pt 15mm deep well with me, and I want to try and remove #1 at a later date

 

[budwich]

wow... that looks like you had / have significant water ingression which "boiled" away the body of the plug. Are you the original owner of the vehicle? I suspect that the mileage may not be correct. you need to be careful trying to remove the "bad plug" otherwise you will be in a "field of hurt" if it breaks in the head. You might want to let the vehicle sit for a very long time with some "liquid wrench" (or equivalent) sitting in the plug well to see if it helps loosen the stuck plug. Good luck.

 

[Mooseman]

Maybe that #2 ACDelco plug is a fake? The has been a proliferation of fakes from China lately. It may have been made with inferior metal and rusted easier. Very strange that not all have been replaced at the same time.

At least you're doing it now. Should help it run much better.

 

[mrrsm]

Your First Option is to STOP and NOT try to remove any Resistant Spark Plugs If the Engine is presently running ...nominally.

However, if you decide to continue on... Please consider that the OO (Original Owner) may have encountered this same difficulty (...were these Plugs Lok-Tited in place or Cross-Threaded with MUCH GREATER than 18 Ft Lbs of Torque?). So when trying to perform the Spark Plug Set R&R , he simply abandoned the idea after encountering too much resistance. He would have had to install the remaining plugs with Brand New Ones wherever they could easily be removed.

Your second option is to Snap Off the upper Porcelain Electrode section and then use a Slender Steel Pin-Punch, to shatter the remaining Porcelain deep inside of the remaining Plug and clean out the Spark Plug Well as you go along using a Shop Vacuum and Compressed "Canned" Air. Then carefully insert an appropriately sized EZ Out and using GENTLY Counter-Clockwise Force... unwind the Remainder of the Spark Plug. If you use TOO MUCH PRESSURE... the EZ-Out will expand the inside of the Plug TOO MUCH and make it even harder to get it out.

Make sure to examine the Spark Plug Threads for ANY signs that the Aluminum Spark Plug Hole Threads came out WITH that Plug. TIME-SERT Makes a Threaded Cylinder Spark Plug Hole Repair Kit if this happens as the BEST possible PERMANENT solution. Avoid using the Helicoil version due to the High Compression of 10+:1 in the GM Atlas 4, 5 & 6 Cylinder Engines that might defeat the Helicoil and make matters much worse:

I recommend using the TIME-SERT Kit from Personal, Successful Experience:

TIME-SERT OEM SPARK PLUG REPAIR TOOL KIT ($240.00 Free S&H):

Amazon.com: Time-Sert M14x1.25 Spark Plug Thread Repair kit p/n 4412E-111: Home Improvement

Buy Time-Sert M14x1.25 Spark Plug Thread Repair kit p/n 4412E-111: Spark Plug & Ignition Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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I'm NOT recommending this Yosoo Kit as I have NO experience with using it. I'm just making you aware of it as a much less expensive alternative:

YOSOO KNOCK-OFF SPARK PLUG REPAIR KIT (Under $60.00 Free S&h):

Amazon.com: Yosooo Spark Plug Thread Repair Kit, 25 Pcs M141.25 Screw Thread Tools Repair Kit with Case: Automotive

Buy Yosooo Spark Plug Thread Repair Kit, 25 Pcs M141.25 Screw Thread Tools Repair Kit with Case: Spark Plug Thread Repair Kits - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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It is imperative that after you Snap Off the Upper Porcelain Electrode to remove every last particle of the shattered White Porcelain B4 Removing the Plug Remainder by thoroughly vacuuming-blowing around that area inside the Spark Plug Well. In the absence of being this fastidious... if any remaining pieces of the Porcelain material were to drop down inside of the Cylinder Head through the vacated Spark Plug Hole, the Cylinder Walls, Pistons, Compression Rings, Valve Seats and Valves could become scored and damaged just after Starting the Engine.

Please ...Wear OSHA Approved Eye Protection when doing this work, as Razor Sharp Flakes of Air-Jetted White Porcelain can easily get ejected upwards and strike or cut into and Penetrate, Damage or Injure your Eyes.