Getting seized spark plug out?

[Scarletpimpofnel]

Years ago I tried to change the plugs on an ancient daily that hadn't had plugs removed for many years. All were stiff but one was stuck fast so I left that as it was.

I need to change the plugs on another car in a week or so and am expecting one or more to also be seized in. What is the best way to get them out? Is it best to have engine hot or cold to get a seized plug out? Can I just use brute force til it shifts or will the thread get damaged?

I'm doing this simple job as a favour for someone and worried I'll end up trashing their head and car!

tia

[E-bmw]

Personally, if I ever come across one not wanting to come out, I generally just move back & forth by the smallest of amounts until it eases, a bit of diesel in the hole can help when it starts to move.

[Lincsls1]

Brute force can result in a snapped plug so don't do that.
Soak in your choice of penetrating fluid for as long as you can. Then try to remove the plugs, easing them back and forth a bit at a time.
Good luck!

[Tye Green]

never had to try this but read elsewhere:

warm the engine up, remove coil /plug lead then fit a deep socket over the plug with a layer of electrical tape to seal the socket around the body of the plug.

fill the socket using plumbers pipe freeze from the top square hole that the extender bar goes into. the plug cools quickly and shrinks

fit the socket extension and unscrew it.

let us know how you get on!

[Megaflow]

E-bmw said:

Personally, if I ever come across one not wanting to come out, I generally just move back & forth by the smallest of amounts until it eases, a bit of diesel in the hole can help when it starts to move.

This, plus getting the engine as hot as you dare before attempting it. I'd be soaking the base of the plug with the diesel for several days before attempting it as well.

[Scarletpimpofnel]

Thanks all, fingers crossed they'll come out easily.

When I was a youth it was almost a weekly task cleaning plugs (my old knackered cars usually were burning oil or running lean etc so plugs needed checking regularly). But nowadays many plugs don't need changing for 30,000 miles and garages don't seem to do it unless asked hence some cars can go way more than that with old plugs in which I think leads to stuck plugs (coupled with people not using the right lube when plugs are changed).

[liner33]

Tye Green said:

never had to try this but read elsewhere:

warm the engine up, remove coil /plug lead then fit a deep socket over the plug with a layer of electrical tape to seal the socket around the body of the plug.

fill the socket using plumbers pipe freeze from the top square hole that the extender bar goes into. the plug cools quickly and shrinks

fit the socket extension and unscrew it.

let us know how you get on!

Never heard of this but it does sound like a recipe to break the porcelain

[aka_kerrly]

Tye Green said:

never had to try this but read elsewhere:

warm the engine up, remove coil /plug lead then fit a deep socket over the plug with a layer of electrical tape to seal the socket around the body of the plug.

Or use a spark plug specific socket which (in my experience should be 6 sided as opposed to 12 side) have a plastic/rubber insert preinstalled which will grip/protect the head of the plug & make removal once undone simple avoiding the need for fishing around with long nose pliers or magnets.

[Boosted LS1]

^ This. How can anyone break a spark plug at the boss? I've never come acoss this and they're not exactly tiddly.

[Tye Green]

the tape made the socket a tight fit onto the hexagon metal part of the plug to stop the plumbers freeze leaking out and ensure it was all held on the plug body , cooling only the plug and leaving the head still hot. the tape then ensured that the socket still gripped the plug to extract it.

I suppose that if the porcelain part of the plug broke off it wouldn't matter since it would be encased in the plug /socket.

[richhead]

Boosted LS1 said:

^ This. How can anyone break a spark plug at the boss? I've never come acoss this and they're not exactly tiddly.

used to happen on the old fiestas, steel plug in an iron head, not often mind, and always due to neglect. Im thinking the old kent engines etc. The actual nut part of the plug, if you know what i mean, wasnt that strong. As the apprentice at a ford garage i ended up being given a few to sort out, But with modern engines i would say unlikely. Although plug changes at huge mile like now cant be a good idea.

[Boosted LS1]

^ what I mean is that as long as you can put a socket onto the plug then surely it'll come out even if the porcelein section's broken off. Have I missed something?

[GreenV8S]

Boosted LS1 said:

Have I missed something?

I've never seen it happen, but I think the problem being described is that the metal part of the plug snaps ie in the same way a stuck bolt might if you try to remove it with brute force.

[richhead]

GreenV8S said:

Boosted LS1 said:

Have I missed something?

I've never seen it happen, but I think the problem being described is that the metal part of the plug snaps ie in the same way a stuck bolt might if you try to remove it with brute force.

this

[Ritchie335is]

It used to happen occasionally with the taper seat plugs in Ford Crossflows & Pintos (non injection), and also the Essex V6 IIRC.
As mentioned, a steel plug in an iron head, with a taper seat can take a good hold if not changed for a while, over-tightened, installed without some anti-seize or a combination of all 3.
They would shear just flush with the head, below the hex part, keep in mind that although the plug looks like it is thick metal at that section, it isn't really as the insulator is inside and the actual sleeve / body section of the plug might only be a couple of mm thick.
I've actually seen myself cautiously using the impact gun to get them to shift back in the day, not advised, however i personally never broke one.

ETA, I'd be surprised if a modern aluminum head would actually grab onto the plug enough to snap it, you're much more likely to tear the threads out with the plug if it is that seized.
Patience is the key, get it moving a little bit and just work it slowly with a good dosing of spray, if it tightens up go the other way, just keep at it and it will come out. If you force it you'll fk the threads.

Edited by Ritchie335is on Saturday 30th March 06:16

[Smint]

This can be an issue with Subarus and probably other cars where spark plug removal is difficult (understatement) so they get left in for years on end, more likely with low mileage older cars.

End up with the thread so tightly stuck that no matter what you do the plug itsell will snap off clean under the nut head, when that happens the tip might drop inside the combustion chamber, in which case the head probably needs to come off.
If the plug does snap but the electrode stays put try a strong vacuum in the plug hole, if lucky the tip and electrode can sometimes be sucked out, you can then try an 'easyout'.
Once in a while nothing will work even an easyout so its head removal and if still no joy then an engineering shop job, which might result in an insert if even they can't shift it and the head design is suitable for an insert.

[donkmeister]

Boosted LS1 said:

^ This. How can anyone break a spark plug at the boss? I've never come acoss this and they're not exactly tiddly.

Well you've just jinxed your next plug change

Make sure to smash your knuckles and burn yourself on the exhaust manifold before your next attempt to remove plugs, in order to appease the spanner gods.

[Boosted LS1]

donkmeister said:

Boosted LS1 said:

^ This. How can anyone break a spark plug at the boss? I've never come acoss this and they're not exactly tiddly.

Well you've just jinxed your next plug change

Make sure to smash your knuckles and burn yourself on the exhaust manifold before your next attempt to remove plugs, in order to appease the spanner gods.

I live and learn everyday :-) Smashing, burning and leaving my dna inside engines is the norm.

[Purosangue]

an old trick of my late father , who had a bent valve on a Rover P5 3 litre

He filled a thermos with liquid nitrogen at work , brought home

He used plasticine to make a "dam" around a stuck side valve , poured in liquid nitrogen , left for 5 mins made a cup of tea , knocked the head with a rubber mallet , and valve fell out . Guessing you could do the same to the spark plug and use a socket to undo once cold enough

[donkmeister]

Purosangue said:

an old trick of my late father , who had a bent valve on a Rover P5 3 litre

He filled a thermos with liquid nitrogen at work , brought home

He used plasticine to make a "dam" around a stuck side valve , poured in liquid nitrogen , left for 5 mins made a cup of tea , knocked the head with a rubber mallet , and valve fell out . Guessing you could do the same to the spark plug and use a socket to undo once cold enough

Make sure you don't use liquid helium as it will climb out of the hole. Hurrah for superfluids.