Two plugs broken off in the head

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Bert

Bert

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Oct 26, 2010
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My newest aquisition a '76 Gl1000 has two broken plugs.

I'm gathering opinions as to how to remove the plug treads that are still in the head. I posted the question on NGW and received some ideas.

The consensus is to heat what's left and quench with a penetrating oli and drive an easy-out in the hole and try to removed the pieces of thread left from the plug breaking off.

Any other ideas are welcome.

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Left in the picture.

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Ford has had this problem on their gas engines for several years now, and there is a tool out to remove the broken ends from the heads without dis-assembly. It's basically just what you described...a square headed ease-out that gets knocked down into the plug, and wrench it out. They also suggest heating and quenching. The tool also comes with a tap to re-thread the plug holes, since the problem seems to be due to either someone removing the plugs while the engine is hot, or cross-threading the plug on install. A little dab of anti-sieze will help later removals of the plugs.
 
I agree with the square EZ out for sure. The round one's tend to "wedge" which puts pressure against the threads and head making it turn out more difficult.
I'd still like to know WHY they broke.
 
They broke because they wouldn't move even a tiny bit using a 3/8" ratchet after soaking the area around the plugs with PB Blaster per Randakk's article on prepping an old wing that's been sitting for years before you try and start it. I'm a pretty big guy and they wouldn't budge when I put the hunker-down on them with the 3/8".

My wing sat for twenty years. Since it only has 13,988 miles on it I'd bet they are the original plugs. I soaked the area with PB Blaster and waited twenty-four hours. The plugs would not budge. I put a 1/2" pull bar on them and they moved...well at least two of them. The other two snapped off. I was moving them an 1/8" inch and re-applying blaster. Going from one side to the other. Two came out cleanly. I had to laugh at my luck because of course one broke off on each side rather than one side. That means I'd like to be able to get at least one of the broken plugs out cleanly then I'm only facing pulling one head.

I just want to hear the opinions of those who have successfully removed the remnants of the plugs without removing the heads. I know this has happened to others before on this forum and I'd like to hear from them. I'm prepared to have to remove the heads but I'd rather not if it's possible to try an alternative.
 
One thing you might try before attempting to remove the slugs...
Run the piston all the way up to TDC on that cylinder. You'll need to loosen the valve adjustments to make sure the valves are closed. Then fill the cylinder with Marvel Mystery oil, or liquid WD40(not the aerosol) all the way up past the casing of the plug that is still in there. Let that sit at least overnight.
With the plug snapped like that, filling the cylinder will allow the penetrating oil to work on the back side of the plug threads, as well as the top side. This would make it hard to heat it with any flame, so you'd need to drain the oil out before attempting to apply heat, but...if the penetrant seeped up on the backside like it should, you may not even need heat.
 
The plug threads probably had some dissimilar metal things going on (steel in aluminum). Just from sitting for so many years. I have removed broken threads by using a carpenters scribe (a long metal pointed item used to scribe lines on wood). The scribe's pointed end cuts into the threads real easy without touching the threads in the head and I collapsed the threads by pushing real hard at a 45 degree angle. Once collapsed, I pulled them out with needle nosed pliers.
 
It appears that only the metal base is stuck in there. If that is the case. You may be able to find a bolt that fits tightly and spot weld it to the broken bit. This would also provide the heat that may help it to loosen.
Another way that might work is use a reverse style drill bit that may actually turn them out as you drill for the easy out.
 
its going to be difficult those threads are stuck welded ....if you could apply some constant counter clockwise pressure and some constant vibration...like a plam sander running hanging on the end of the counter clockwise pressure it will come loose after some time maybe hrs. along with wd40 like stuff being used im not sure how you would set that up ......you are proably going to loose the threads any other way ......and loose the threads this way to....good luck bert i know you will come up with something.....when i farmed i had to come up with all kinds things to make something come apart out in the middle of nowhere :mrgreen:
 
I managed to get one out cleanly. The other isn't going to budge. I guess I'll drill until the threads are just a coil and then try to pick it out. If that doesn't work then I will try a heli-coil. If that doesn't work I'll pull the head and have the plug hole welded up and drilled and tapped.

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I am more than a little curious as to why Honda uses such a deep threaded part of the plug as you can see in the pictures. (The top right plug and far left) shows the part hanging into the combustion chamber is black and only half of the threads are actually in the head the silver part. Why on earth did they do that? Or are these the wrong plugs perhaps?
 
good eye chas :mrgreen: thats the right plug ....i have heads around with plugs in them i dont remember them sticking down like that .....but maybe so ill look tommarrow :mrgreen:
 
joedrum":2fzlmn6g said:
ididnt notice that...heck what is the numbers on them :mrgreen:
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The plugs are NGK D8EA's.

Yea Joe take a look at the combustion chambers with the plugs installed. I'd like to know for myself. If they are not sticking out in the combustion chamber then why or how did they turn black on the ends?
 
Omega Man":1nr438nd said:
Bert, if you drill it out won't shavings drop into the cylinder? Just a thought, then again what your about to do is out of my "shadetree" league in mechanics.

~O~
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Yes shavings will drop into the cylinders but several blasts of 175 PSI with a fine point blow gun will remove all but the tiniest pieces. I will also probe around with a small magnet. I don't believe that those tiny shards that may or may not be left behind will affect much. Probably they will blow right out the exhaust valve. I pulled a plug once where the ground electrode had fallen off and was nowhere to be found after looking inside with a bore-a-scope. It had to have passed the exhaust valve and traveled to the muffler.
 
joedrum":5xu1wz4r said:
well bert the plugs dont stick down at all .....so now what do you think..... :mrgreen:
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Dad-gum Joe...I really can't explain how at least half of the plug threads are silver at the top and the other half black with carbon towards the bottom. I wonder if any of the experts would chime in and explain it. I see it with my own two eyes but if you say those black threads are not exposed then I don't have a clue.
 
You will normally get discoloration that far up the plug threads it has nothing to do with how far the plug extends into the combustion chamber. In fact if the plug is that far into the chamber it would be hitting the piston top every revolution. It's just blow-by traveling up the threads.
 
fastmover83":1v2zq81q said:
You will normally get discoloration that far up the plug threads it has nothing to do with how far the plug extends into the combustion chamber. In fact if the plug is that far into the chamber it would be hitting the piston top every revolution. It's just blow-by traveling up the threads.
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Thanks for the info.
 

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