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[JamesV6CDX]

I've no record of when the spark plugs were last changed on my 3.2, so thought I'd pop a set in.

The 2-4-6 bank, all the plugs were pretty much only finger tight. Replaced these, no problem.

The 1-3-5 bank, the front two plugs were tight, but came out OK, quite easily with a little plus gas.


Now, the number 5 plug...

Was incredibly, stupidly tight. I gave it a good soaking in plusgas and left for a few hours, before even attempting to undo it.

I got it moving, but it was incredibly tight, when really, the ratched should have required minimal force to undo it, after initially loosening the plug.

More plusgas, more plusgas, and more plusgas!

It was about half way out, I was working a little bit at a time in each direction, being as gentle as I possibly could with the thread.

When I finally got it out, I noticed that the thread on the end of the plug, probably a third of the thread, is absolutely mullered   :-/ It was like it was welded to the head.

Upon inspection, the thread inside the head looked absolutely fine.

I blasted it out to remove any potential crud / swarf, and inspected it with a device that let me see right in there. Looks fine.

A new plug has threaded in centrally, and torques up without any problem at all,

Question is, what causes the plugs to become so "set" in the heads. I've never had one quite like that to remove, on a vauxhall, before.

I don't think it was originally crossed, because the thread in the head is fine, and a new one goes in perfectly central.

Anyone else had this?

Must say, it was a bit of a 'oh sh!t' moment, when I first saw the thread on the plug 


(Edit by jv6cdx - spelling)

[Kevin Wood]

I'd say it's most odd that the plug thread got mullered but the much softer cylinder head was fine. :-/

A bullet dodged there.

[JamesV6CDX]

I'd say it's most odd that the plug thread got mullered but the much softer cylinder head was fine. :-/

my thoughts too!

I honestly thought, I'd be looking at helicoiling the head, when I saw that!

[blackviper90210]

I'd be crying if that had happened to me! Just glad it worked out ok, nice one 

[JamesV6CDX]

Ah it's ok, worst case I'd have taken the head off to sort it - not a problem really, as I don't use the car for daily work - just inconvenient! 

[Abiton]

Had something similar, but the plug thread wasn't damaged as far as I recall, just clogged to buggery with that limescale-like, but-not, stuff that you can get when a plug thread has been leaking combustion gases for quite a while.

That description of the torturing extraction process, and anxiety, followed by relief when the new plug went in fine, is very, very familiar.

May or may not be related, but not long after, I discovered a (very slow, very slowly worsening) HG leak of coolant into that pot. 

[Bent valve]

I've no record of when the spark plugs were last changed on my 3.2, so thought I'd pop a set in.

The 2-4-6 bank, all the plugs were pretty much only finger tight. Replaced these, no problem.

The 1-3-5 bank, the front two plugs were tight, but came out OK, quite easily with a little plus gas.


Now, the number 5 plug...

Was incredibly, stupidly tight. I gave it a good soaking in plusgas and left for a few hours, before even attempting to undo it.

I got it moving, but it was incredibly tight, when really, the ratched should have required minimal force to undo it, after initially loosening the plug.

More plusgas, more plusgas, and more plusgas!

It was about half way out, I was working a little bit at a time in each direction, being as gentle as I possibly could with the thread.

When I finally got it out, I noticed that the thread on the end of the plug, probably a third of the thread, is absolutely mullered   :-/ It was like it was welded to the head.

Upon inspection, the thread inside the head looked absolutely fine.

I blasted it out to remove any potential crud / swarf, and inspected it with a device that let me see right in there. Looks fine.

A new plug has threaded in centrally, and torques up without any problem at all,

Question is, what causes the plugs to become so "set" in the heads. I've never had one quite like that to remove, on a vauxhall, before.

I don't think it was originally crossed, because the thread in the head is fine, and a new one goes in perfectly central.

Anyone else had this?

Must say, it was a bit of a 'oh sh!t' moment, when I first saw the thread on the plug 


(Edit by jv6cdx - spelling)

What did you blast it out with, Dynamite? seriously though, did you use an airline? I always use a small bore pipe connected to a hoover to remove crud were there is chance crap could get into the engine