Cross Threaded Spark Plug

If he's got it out easily it's unlikely to be cross threaded unless he started to put it back and then stripped the threads. If he has then I guess heli coil is the way to go but I believe it is a garage job involving drilling out the hole and inserting the helicoil insert (as it were).

Has he tried a spot of oil on the threads first?

-- Malc

The message from "Malc" contains these words:

Or a thread chaser?

Try another spark plug first.

Cross threading is more likely to occur when replacing a plug, but if it hasn't been cross threaded in the attempt to replace it, the thread could have been damaged as it was removed. It's not unheard of, for a plug to sieze in this way, leaving the thread too damaged to allow the plug to be easily replaced. If that has occurred the thread on the plug will show it. Try fitting a new plug. If that's not successful, it might be better to let a garage look at it it. With luck it can be rescued just by cleaning it out with a plug tap. At worst it will need a Helicoil insert. Either way it shouldn't cost more than £20-30 I could suggest cutting or grinding the thread on an old plug to create a rough tap, but without a certain amount of expertise it could be made worse than it is now. Mike.

Cross threading is more likely to occur when replacing a plug, but if it hasn't been cross threaded in the attempt to replace it, the thread could have been damaged as it was removed. It's not unheard of, for a plug to sieze in this way, leaving the thread too damaged to allow the plug to be easily replaced. If that has occurred the thread on the plug will show it. Try fitting a new plug. If that's not successful, it might be better to let a garage look at it it. With luck it can be rescued just by cleaning it out with a plug tap. At worst it will need a Helicoil insert. Either way it shouldn't cost more than £20-30 I could suggest cutting or grinding the thread on an old plug to create a rough tap, but without a certain amount of expertise it could be made worse than it is now. A smear of Copperslip or Copperease on the plug threads should prevent a similar occurence in the future. Mike.