Simple question: Has anyone ever heard of a spark plug working its way out of the holes. Compression shoved it upward and the coil bolt bracket broke off. The threads weren't damaged and the plug was ok too. I did have to get new coil. Could it be too much anti seize or the silicone I put on the end of the coil to be able to take it off later. Only thing I noticed is that the coil tip had carbon on it and so did the exposed plug, so it had been wandering around loose for a while. The threads were all good too. Possible causes: I didn't tighten the plug and it was only hand tight. That's all I know except how it turned itself around.

Fire away. BTW this wasn't on my Jag, but the only expertise I trust is here.

 

Depending on the application, anti-seize or other lubricants should not be used on the spark plug threads as some are lubricated already from the manufacturer.

If the spark plug has worked its way loose, remove the spark plug completely and clean or chase the threads in the cylinder head to remove the carbon. Install a new spark plug and coil unit.

 

I highly recommend an expanding back-tap thread chaser, such as the Power built #640811:

https://www.powerbuilt.com/products/...ir-tool-640811

Not sure which size you'll need, so double check before purchase.

This type of thread chaser is slicker than snot in a Minnesota winter. The business end collapses to reach undamaged threads deeper in the hole. Then it expands and you back it out to repair any damaged threads. This ensures the repaired threads remain in alignment. Any shavings are pulled out, too.

With a conventional solid tap, it cuts as threaded into the hole. It's easy to get cross threaded and stuff up the whole thing. Plus, it pushes any debris into the cylinder, even if greased up to catch shavings.

 

I did use anti seize on the plug. It was in there about 110,000 miles. I will drive it a bit and them take it out and replace it with a new one. Thanks.

 

Great to know. I just read their website about how it works. I'll order one as soon as I get the size. Thank you so much.

 

needs an insert

spark plugs shooting out is because of lack of threads (ford triton) or just loose

 

Hi David,

xalty may be right about your threads - it would be prudent to have a good look at them with an endoscope. You can buy a cheap USB endoscope (a.k.a. bore scope, inspection scope) on Amazon that will work with your smartphone.

As xalty hinted, if the threads are damaged, they can be repaired with a threaded insert. Helicoil is a popular brand. If you haven't installed an insert before, this is a job for a professional.

Most modern passenger car and truck spark plugs are plated and the use of anti-seize is no longer recommended. NGK calls it's treatment "trivalent plating."



Cheers,

Don

 

I am beginning to think loosened up or was never tightened. #2 plug measure was 3.25" from top of the hole to plug top. Re-installed #3, tightened and got the same measurement.
New plugs arrive today. Will use my inspection camera before I put it all back together and be sure the threads are good. I bought the tool to re-thread it, but may not need it. That will go in the tool chest.

 

They are NKG plugs. New plugs arrive today. No anti seize this time. I looked at the threads with my scope/camera. They look good.

Thank you.

 

A 'lil bump:

For the first time ever in almost 50 years of wrenching, I managed to cross thread a spark plug and damaged the first couple of threads. This was on a cast iron head on the 351W in my pickup. Oh anyways, I finally took my Powerbuilt back-tap out of the wrapper. It cleaned up the threads like magic. I can recommend this tool without hesitation. Buy one now before you need it and save yourself some aggravation.

 

Good gracious, 110,000 miles?!😮
I’m fairly sure you’re supposed to replace them at about 40-50,000.

 

Ordered mine yesterday! Thanks for the tip, Karl!

Cheers,

Don

 

I may have mis-written that. The plugs were put in at 110,000. There is a 152,000 on it now so this was a 40,000 mile change.

 

Ah, I see.That’s not so bad then👍😂

 

damn. That sucks! Ive never done it but im always fearful of it. Or breaking a plug off at the threads. I am confident in my abilities and somewhat competent but you hear about it happening so I know we can all be victims of a major **** up.

if it makes you feel better I didnt tight an oil filter enough for some reason I cant explain and it loosened. First time in 45 years! Happened just recently and ive overtightened each subsequent filter due to my recent paranoia. I still cant explain how I left it loose. I swear I always go one turn past contact.

once I tapped main bearing thread on a mopar with a metric tap. Because I matched the tap to the main cap bolts they gave me (and said went to that block BUT THEY WERE WRONG and they werent for the block). I still built it though. and it is still running. Im shocked but laughing

 

Karl,

I just wanted to thank you again for the tip on the Powerbuilt 14mm Back Tap 640811. On your recommendation, I ordered one and put it in the drawer with my metric taps & dies and thread chasers. I'm very glad I did.

I just R&R'd the plugs, wires cap rotor and points on a 1972 Mercedes-Benz 350SL (R107) with the 4.5L M117 V8. All the plugs were a little loose, except plug 7, which would not turn out smoothly. I carefully worked it in and out and sprayed it with penetrant, but when it finally came out, the plug threads were rusty and had traces of fresh metal on them.

Even after cleaning the plug port threads in the head with a wire bottle brush and solvent, the new plug did not want to thread in. So I tried the back tap, and after a couple of tries, gradually tightening the knurled nut a little more at a time, I got the threads in the head cleaned and re-formed. The new plug threaded in easily and torqued perfectly.

On the M117 engine the spark plugs are fairly deeply recessed and down on the side of the engine, so using a standard spark plug thread chaser would have been difficult, and having to do a helicoil insert with the head in situ would have been a nightmare. But the additional length of the back-tap and the fact that it can start from the deeper, undamaged threads and work backward/upward through the damaged section of threads makes it truly invaluable.

Thanks again for the great tip! And for those of you who haven't ordered yours, they're currently on sale at Amazon.

Cheers,

Don