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stuck spark plug in aluminum head

Tracy T

Subscriber
Last Subscription Date
07/16/2019
anybody got any ideas how to remove it without taking the threads along with it? oddball sparkplug size too 18 MM. I dont know if they make a helicoil for a 18 MM spark plug. I can move the plug very little then it gets tight, go the other direction the same amount and tight again. I have worked it several times, it aint giving it up!
 

Pat Barrett

Subscriber
Age
71
Last Subscription Date
01/02/2020
Try to find some Tap Magic for aluminum and squirt some of that around the threads and work back and forth. 18mm Spark plug helicoils are available. I just looked, I've got a 10mm x 1 and a 14mm x 1,25 but not the 18,or I'd offer to mail/loan it to you.
 

J.B. Castagnos

Registered
Last Subscription Date
01/01/2006
It's probably galled, aluminum stuck in the threads. If you unscrew it will probably take the aluminum with it. Is the plug in the open, can you possibly remove the porcelain and cut the steel on two sides and collapse it? Probably the only chance of saving the threads. Air in through an open exhaust valve will blow shavings out as you machine it.
 

K-Tron

Registered
What engine are we talking about? Briggs, Tecumseh, Kohler, Wisconsin? You can break off the porcelain with a hammer, punch out the center electrode and then use a small hacksaw to cut away the sides of the plug so you can collapse it. You can alternatively impact it on out and have the head helicoiled. Some heads are not worth the effort to repair, but many times the older Kohler and Wisconsin heads can be repaired with little effort.

Chris
 

I like oldstuff

Registered
Last Subscription Date
11/09/2015
Lube the snot of the threads and keep rocking it back and forth. There is certainly a bit of aluminum stuck to the steel thread.

You can heat the plug with a torch also. Sometimes this will release the aluminum with the steel bond.
80% chance there will be damaged threads once it's out.
 

gustavus

Banned
Lube the snot of the threads and keep rocking it back and forth. There is certainly a bit of aluminum stuck to the steel thread.

You can heat the plug with a torch also. Sometimes this will release the aluminum with the steel bond.
80% chance there will be damaged threads once it's out.
VG4D Wisconsin had four seized spark plugs, heat n cool several times over the course of a few days did its magic.

WD40 then used the pneumatic impact, no damage to the threads.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
wisconsin vh4d. removing the head is not a problem, i have left it in place because the engine does a better job holding it than i ever could! may try some heat and see what happens. I have looked around for another head (worse case) and they are $$$$$$ and who is to say you wouldnt end up with the same problem.
 

ronm

Subscriber
Last Subscription Date
07/10/2019
18MM is not an "oddball" spark plug, common as hell on older stuff. I have a kit with a rethreading tap and inserts for both 14 & 18MM, made by K-D I think.
 

M.Canute

Registered
Alum will dissolve steel but not aluminium. From wiki: "Potassium alum, under the name "alum powder", is found in the spice section of many grocery stores in the US. Its chief culinary use is in pickling recipes, to preserve and add crispness to fruit and vegetables."
"Alum solution has the property of dissolving steels while not affecting aluminium or base metals. Alum solution can be used to dissolve steel tool bits that have become lodged in machined castings."
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
18MM is not an "oddball" spark plug, common as hell on older stuff.
well it sure is a odd looking duck to me anyway, had my parts man stumped as well. I have to go to the parts store today and the tractor shop as well, maybe the tractor shop will be of more help locating a helicoil. A helicoil is probably going to be the way to go if all else fails. Interesting info regarding alum, wonder how stought of a mixture and how long that would take?
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
looks like i may be stopping by the local grocery store too!:rotfl: learn something new everyday around here!:D
 

miltruck

Registered
Cheap inserts with tools on e-bay and amazon all the time. Use the correct ones specifically for the sparkplugs. Do it once and you will never touch it again.
 

M.Canute

Registered
This is the coolest trick I've heard in a long time. I've never heard of alum dissolving steel. Here's a youtube of a fellow using battery acid and alum to dissolve a 4-40 tap out of an aluminum block...

https://www.youtube.com/watch?v=hHN0v2wYjXQ

Thanks!

Kevin
The guy's somewhat clueless. The sulfuric acid reacts with aluminium to produce aluminium sulfate and release hydrogen gas and is not needed at all. He should have just used water to dissolve the alum in.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
well so far just running it a bit and trying again has yielded 1/16 of a turn. neither place was any help with a helicoil repair kit. will dig some more online to see if i can come up with anything...
 

DustyBar

Subscriber
Last Subscription Date
01/03/2019
Oreilly Autoparts lists that size on their web site. Would that be M18x1.5 or M18x2.5? They show both as being available. Complete kit with installer and tap my cost more than a new head....don't know.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
thats what i am running into also, all kinds of stuff on the market for the ford triton and for 14 MM. I will have to check the threads with a thread gauge. may be just well off leave it alone, I cant load the engine at the moment to generate any real heat. will have to think on this.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
this would be a snap in a mill with x,y,z readout. find center and go all 4 directions just shy of the threads. my neighbor has this setup and has been after me to get one too. after watching him do some of the stuff he has done I am about ready to pull the trigger on one!
 

Tanner Remillard

Subscriber
Age
36
Last Subscription Date
07/10/2019
Usually when aluminum or stainless threads start to gall, you're done. When I bought my Harley used several years ago I went to change the spark plugs and the rear cylinder pulled the threads right out of it. I used a 'Time-Sert" kit, and it worked very well. You can find them on Amazon. They aren't a cheap kit, but like said, do it right and you wont have to do it again, plus pulling the head wasn't necessary. You do get some chips in the cylinder, but they can be blown out. This happened probably over 50,000 miles ago and its working just fine.

I've NEVER been a fan of heli-coil. Some guys love them, but to me they are just a band aid fix, and as a machinist I cant tell you how many times I've had to repair threaded holes that someone put a heli-coil in it and it just failed again. A true threaded steel insert like a time-sert or keysert is the way to go.

And, I always anti-seize the shit out of the spark plugs when putting them back in, especially aluminum. For that matter I put anti-seize on pretty much every fastener for aluminum or stainless.
 
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