Cross threaded, over torqued, or under torqued during instillation
You have to get a helicoil and follow the instructions. A helicoil is a new set of threads that you install in the old socket. Hope this helps
Do NOT use a helicoil. A good repair shop or machine shop will have the tools to install an insert which becomes a permanent repair. A helicoil will come out when the spark plug is removed and cause further damage to the cylinder head.
find the right size helicoil and drill out the hole to the proper size and install
helicoil
A helicoil kit will come with directions, special size drill bit, special size tap, helicoil install tool and the helicoil. First you drill out the hole with the drill supplied, tap the new hole with tap supplied, screw in the helicoil with supplied tool then snap off remaining tab and yes some metal ends up in the cylinder. If the metal scraps are steel you can withdraw most of it with a magnet if it's aluminum they will have to pass thru the system on their own. Crisco smeared in the flutes of the tap will trap most of the metal shaving.
Helicoil kits can be gotten from many places. Stores that specialize in sell these types of products or stores such as Lowes and Home Depot will also sell them.
No. Helicoil
Helicoil.
If the spark plug is stripped, replace it, if the hole in the cylinder head is stripped, the first thing to do is run a tap or thread chaser through the hole, if that does not work, you will need a helicoil http://en.wikipedia.org/wiki/Helicoil
In an item into which a bolt goes, the item can be repaired by using a helicoil insert, once the damaged thread has been prepared to a larger size using a helicoil tap. The insert has a matching larger outer diameter, and has an inner diameter to match the original thread size. Also an inserting tool is needed, so best to purchase a kit with all parts in. One company that makes the helicoil items is called Re-Coil.
Many auto parts stores sell a helicoil thread insert kit that will replace the damaged or missing threads. The kit should include an installation tool that will reach down into where the spark plug was removed. The kit will have instructions on enlarging the stripped hole and creating new threads for the helicoil or steel insert. A new spark plug should thread directly into the new thread insert.
Ask the garage for a helicoil repair.