Thank you very much. The DOHC 2.4L head in this 2001 PT Cruiser spit the No. 1 spark plug without warning, taking the threads along for the ride. We suspect this resulted from poor thread quality coupled with a relatively low spark plug torque value. It appears that cylinder pressure worked its magic on the threads, finally causing the threads to fail.
Even with the cover removed (which requires removal of the intake manifold and coil pack), the plug threads are really buried down at the bottom of deep plug bores, so long tooling is needed to perform the job.
Goodson to the rescue. The spark plug repair kit (P/N FT-514LTK) includes everything needed to perform the fix. The kit is universal for a variety of heads, requiring only the proper-length inserts for any specific application. Inserts of all popular lengths are readily available.
In order to bore out the existing spark plug hole, the kit includes a long two-step reamer. The small nose indexes into the existing hole, while the larger-diameter cutters will increase hole diameter in preparation for tapping new threads.
A handy centering adapter is slipped onto the reamer shank. This adapter is shouldered, allowing the lower portion to enter the top of the hole, while the adapter's larger diameter shoulder rests on top of the head. This allows centering alignment of the reamer to prevent the reamer from working at an off-angle.
While not needed in every situation, the kit's seat boring tool can be affixed to the reamer to cut a new seat to ensure that the thread insert's installation tool bottoms out, ensuring proper installation depth of the new insert.
The inserts required for this job (P/N FFT-514125LA) feature a 14mm x 1.25 internal thread and an overall length of 1.00". The inserts are made of hard anodized aluminum instead of steel. This makes the inserts compatible with an aluminum head. The external threads feature a unique pitched thread made by Lock ‘n Stitch that creates a strong, no-back-out installation. The inserts include 1/16" locking pins, as well as added insurance against future insert back-out during any future spark plug service.
Even though we applied grease to the reamer to help prevent chips from entering the chamber, after reaming and tapping, we vacuumed any remaining aluminum chips using a shop vacuum, necked down to a 1/2" rubber hose that we inserted into the cylinder. We inspected the bore using a bore scope, assuring ourselves that all debris had been removed.