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'07 Cobalt LS, vanilla 2.2

I may have to remove the (probably 10-year-old) spark plugs, which I suspect may be stuck. If so, I'm wondering if it would be prudent to hit them with an impact wrench to break them free.

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    Side thought - make sure your spark plug socket is a decent fit - minor tolerance variations can rob you of torque. Compare a removed plug with your socket. And use anti-seize when fitting new plugs. – Criggie Nov 9 at 21:31
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    Is there actually a problem here or is this premature optimization? – Caius Jard Nov 10 at 17:47
  • In the end IF they will not come out using wrenches you may have to use an impact carefully, they have an advantage of creating vibrations which help loosen frozen threads, its better if the engine is very hot when attempting removal of the stuck spark plugs. If they are truly seized in the head, it does not mater what method removes them the threads will get pulled out with the plug. – Moab Nov 13 at 16:34
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In a word:

NO!

Please do not use an impact wrench on these. You run the distinct chance of stripping out all of the threads in the head, which will cause a huge nightmare for you having to have threads replaced (Heli-coil or the like). Just use a socket/ratchet and you'll be fine.

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    Or snapping off the body and leaving the plug threads in the hole... – Solar Mike Nov 8 at 17:02
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    If you are having trouble use some penetrating fluid like WD40, and give it time. Engina the goddess of motors will not be happy with you if you use an impact wrench on spark plugs. – GdD Nov 8 at 17:31
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    @GdD My tried-and-true formula for loosening any threaded object has always been some combination of heat, PB Blaster, and time. – smitelli Nov 9 at 0:35
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    @Tonny most spark plugs I've seen has some sort of metallic seals. WD40 is not corrosive, and will not eat away the seals. It may penetrate the seal if it's not perfect, however. – vidarlo Nov 9 at 13:00
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    @Tonny not seen any spark plugs with plastic seals or rubber ones.. spark plugs have metal compressible washers to make the seal. – Solar Mike Nov 9 at 17:17
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Use PB Blaster(the BEST),NOT WD-40(Water Displacement Formulation 40) or any brand of penetrating solvent,Liquid Wrench,etc. An impact wrench is a formula for disaster. Use a breaker bar to get the plug to move just a bit is good,apply more penetrant and,hard as it may to do so,WAIT. Days,even.If you can get the plug to move, even a bit counter-clockwise,re tighten it clockwise,then back the other way. Do this many times to slowly work the plug out. Be aware,muscling it out counterclockwise without going back and forth.counterclockwise,then clockwise, MAY damage the head beyond use. This is especially true of aluminum heads. Due to the plug threads reaching INTO the combustion chamber,Triton engines are very prone to damage when removing plugs. No matter what method is used on these engines,the head may be scrap when removing the plugs are attempted. By ANYONE,period.

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