Loose spark plug

[cornwallis]

I have a 99 Limited with 155k miles. The other day I noticed a spark plug wire loose. Took it to the shop. Spark plug was loose as well. They tightened the plug and the plug wire still pops off each time I drive the vehicle. Took it back to the shop and they told me that the threads are really messed up for that one plug. Not the plug itself, but on the motor. I have no warning lights come on inside the vehicle.

If the threads are really messed up and the wire keeps popping off, i don't want to invest $2k as they said it would be to fix this problem.

I am interested in any ideas you might have.

 

[TheBlueWave]

I have a 99 Limited with 155k miles. The other day I noticed a spark plug wire loose. Took it to the shop. Spark plug was loose as well. They tightened the plug and the plug wire still pops off each time I drive the vehicle. Took it back to the shop and they told me that the threads are really messed up for that one plug. Not the plug itself, but on the motor. I have no warning lights come on inside the vehicle.

If the threads are really messed up and the wire keeps popping off, i don't want to invest $2k as they said it would be to fix this problem.

I am interested in any ideas you might have.

$2k for bad threads? That seems really steep. If you have good mechanical aptitude or experience, get a tap and die set and cut yourself some new threads. You may need a slightly different sized spark plug, but jeez for 2 grand as an alternative...
Just be careful and do it very precise, cutting the threads at the exact angle. It may seem daunting at first, but its not hard. I have done it for a lawnmower that had an aluminum head, still runs fine.

 

[wolfgang]

There are threaded inserts (helicoil) that can be used to replace the old threads. They tap out the hole to oversize and then insert the new threads. They work great. Probably messed up by whomever changed plugs last --- or the time before. I always put antiseize compound on the sparkplug threads.

http://www.popularmechanics.com/automotive/how_to/4212608.html

Another alternative is JB Weld - insert with a new plug - and you'll get another 30k or so out of it.

 

[greasefingers]

The engine head would have to be removed, drill out the spark plug hole to the next size bigger, and then tap the hole for the external heli-coil thread. The internal thread is what is important. It must match the spark plug thread. Not sure if heli-coil is used for this application?

 

[wolfgang]

If (big IF) you can get the tap in to do the Helicoil - it can be done without removing the head. Run piston to bottom of stroke for that chamber. Stuff rope in hole - add thick white grease. Then tap to larger size of the Helicoil. Suck loose shaving out with vacuum then removed the greasy rope which should catch the rest. Using locktite insert the helicoil. Then put antiseize on new plug and insert it. Volia - <$30 vice $2k.