Stuck spark plug…any advice please

Superflyguy

Superflyguy

Junior Member
Messages
53
Hi Guys,

Set about servicing my Spyder today and have changed over the spark plugs. However, all have come out fine bar one which appears to be stuck. I am very mindful that I do not want to strip the threads at all costs.

My plan is to soak the plug in penetrating oil and leak over night. Then tomorrow I’ll start the car up and get it nice and hot and have a try again in the hope the block has expanded slightly to help break it free.

Anything else I can try? I once threaded a TVR v8 block and had to remove the heads to repair…the thought of having to do that on a Maserati doesn’t bear thinking about…

Cheers

Guy
 
Superflyguy

Superflyguy

Junior Member
Messages
53
allandwf said:
Just a thought, but what expands more, the plug or the head, it may get tighter?
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I watched a mechanic on YouTube who recommended with an aluminium engine and stainless steel spark plugs the best way to remove a stuck plug was to heat the engine up.. I’ll hold fire on that idea though until I get some more feedback from others.
 
conaero

conaero

Forum Owner
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34,643
You won’t strip the threads, if it goes the spark plug will snap leaving the thread in the head, then you have a massive problem.

Heat cycle is the first port of call, failing that let it cool and shock the plug by hitting the socket grip with a screw driver in the direction of release….medium hard not twatting it then try again with the socket

If in doubt just leave it
 
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Superflyguy

Superflyguy

Junior Member
Messages
53
conaero said:
You won’t strip the threads, if it goes the spark plug will snap leaving the thread in the head, then you have a massive problem.

Heat cycle is the first port of call, failing that let it cool and shock the plug by hitting the socket grip with a screw driver in the direction of release….medium hard not twatting it then try again with the socket

If in doubt just leave it
Click to expand...
Thank you, really appreciate the help - assume I’ll need to change all of the new plugs back to the old plugs to run the engine. I’m replacing the NGKs for Denso plugs so assume wouldn’t be good to mix the two even if it’s just the once to heat the engine up
 
Nibby

Nibby

Member
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2,112
Yeah that trick was tried on Triumph Stag cylinder studs with the different expansion of the aluminium head and steel studs unfortunatey it rarely worked. Another trick was to make a little dam round the stud out of plasticine and feel it with diesel/ Plusgas so it had constant freeing agent trying to penetrate stuck stud. Might be worth a try. The other one but be careful is to slightly try to tighten the spark plug and then try to undo it.
Best of luck.
 
Nibby

Nibby

Member
Messages
2,112
Superflyguy said:
Thank you, really appreciate the help - assume I’ll need to change all of the new plugs back to the old plugs to run the engine. I’m replacing the NGKs for Denso plugs so assume wouldn’t be good to mix the two even if it’s just the once to heat the engine up
Click to expand...
Shouldn't think that'll matter, leave the 7 new ones in there, they should be cross referenced as suitable for your car whatever brand they are.
 
mjheathcote

mjheathcote

Centenary Club
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9,045
The concern, is why is it stuck? Can't see why it should be, unless it was cross threaded going in. Check carefully the threads on the plug when it comes out.
Slight thread drift I had failure on a spark plug on my M140i last week. Only a month and less than 2k miles after the main dealer changed them on a routine major service. Never had a 'new' spark plug failure before, through the car into limp mode after giving it the beans, shall we say.
 
Superflyguy

Superflyguy

Junior Member
Messages
53
mjheathcote said:
The concern, is why is it stuck? Can't see why it should be, unless it was cross threaded going in. Check carefully the threads on the plug when it comes out.
Slight thread drift I had failure on a spark plug on my M140i last week. Only a month and less than 2k miles after the main dealer changed them on a routine major service. Never had a 'new' spark plug failure before, through the car into limp mode after giving it the beans, shall we say.
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Could it be carbon build up or corrosion? To be fair, I’ve be using a spark plug removal tool which is a 16mm socket with a UJ attached to a thin T bar. It’s a bit lightweight. I’m going down to halfrauds shortly to buy a new 1/2 drive 16mm deep socket as mine is missing from my socket set. Hopefully with an extension bar and a large rachet that’ll provide a bit more pressure and it’ll break free. It’s been soaking overnight in plusgas. Fingers crossed
 
Scaf

Scaf

Member
Messages
6,614
Superflyguy said:
Could it be carbon build up or corrosion? To be fair, I’ve be using a spark plug removal tool which is a 16mm socket with a UJ attached to a thin T bar. It’s a bit lightweight. I’m going down to halfrauds shortly to buy a new 1/2 drive 16mm deep socket as mine is missing from my socket set. Hopefully with an extension bar and a large rachet that’ll provide a bit more pressure and it’ll break free. It’s been soaking overnight in plusgas. Fingers crossed
Click to expand...
Sounds like a sensible approach to me - good luck
 
mjheathcote

mjheathcote

Centenary Club
Messages
9,045
Superflyguy said:
Could it be carbon build up or corrosion? To be fair, I’ve be using a spark plug removal tool which is a 16mm socket with a UJ attached to a thin T bar. It’s a bit lightweight. I’m going down to halfrauds shortly to buy a new 1/2 drive 16mm deep socket as mine is missing from my socket set. Hopefully with an extension bar and a large rachet that’ll provide a bit more pressure and it’ll break free. It’s been soaking overnight in plusgas. Fingers crossed
Click to expand...
If just a lightweight, that is probably the issue.
I always use my half inch socket set and don't even think about it they just come straight out!
 
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