Socket size for sparks plug?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Luna3, Jul 4, 2016.

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  1. Luna3

    Luna3 Junior Member

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    Happy 4th all!

    My fresh set of NGKs were delivered yesterday and I dug around the tool box for a plug socket. Hmmm. I've poked around here and 9/16 seems to be the needed size. But I put a wrench of the plug and 14mm appears to be the number.

    Are the OEM Denso plugs 9/16 and NGK 14mm? I know there's a hair's difference in size, but can anybody confirm? A 14mm socket might run around 20 bucks...
     
  2. Kenny94945

    Kenny94945 Active Member

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    Not confirm...I believe they are 14 mm.

    Yet, IMO....the right tool for the job. A specific spark plug socket is best for your tool box. Ever break/ crack the porcelain of a plug without the right tool?

    Have fun with your project.
     
  3. Luna3

    Luna3 Junior Member

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    You know it, especially plugs that are $10 each!
     
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    9/16" = 0.5625 inch
    14 mm = 0.551 inch

    The difference is 2%. The correct size is 14 mm for either Denso or NGK. However if you have a 9/16" spark plug socket, you can use it.

    If you don't have a spark plug socket with the rubber lining, then it would be a good idea to buy a 14 mm spark plug socket.
     
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  5. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    I used 9/16" ok. Good to know 14mm is the kosher size though, slightly snugger.

    I bought a decent set of swivel sockets through Princess Auto a while back, for around $20, since I didn't have 9/16".

    image.jpeg
     
    #5 Mendel Leisk, Jul 4, 2016
    Last edited: Jul 4, 2016
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  6. Luna3

    Luna3 Junior Member

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    I was at first a bit confused...and now I am not. Between the bike, three vehicles, two garden tractors, a weed wacker, and an ice drill, you would think I'd have a complete set of plug sockets...nope, just a couple of rusty junkers in the tool chest. Maybe a magnetic set would be trick.
     
  7. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Rubber inserts that grip the plug are the norm, work good. One of those telescoping magnetic grabbers might help, though if the plug dropped off it could be bad: bend the electrode.
     
  8. ChapmanF

    ChapmanF Senior Member

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    Well, the way it seems to me as I look back is, I spent more than the first half of my life with one spark plug socket that seemed to work on everything I ever took apart. I think I was 32 when I first bought a vehicle that made me go buy a 5/8" plug socket, so then I had two, and that kind of annoyed me.

    And now here I am, upgrading from one generation to another of the same dagnabbed car model, and having to go buy yet another spark plug socket. What'll they think of next? :)

    By the way, anybody know whether the spark plug well is wide enough for a 5/8" socket to fit down? The reason I ask (knowing the proper spark plug socket is smaller than that) is that this smaller M12 spark plug thread doesn't match the hose on my leakdown tester. There's an adapter that comes with the hose, but that has a 5/8" hex. In case I ever get the situation where my hose unscrews leaving the adapter down there, I'd need a 5/8" socket to get it out, which would be no fun if the socket won't fit.

    -Chap
     
  9. CR94

    CR94 Senior Member

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    Car batteries with skinny non-standard (at least in the US) battery terminals? Cooling systems without radiator caps?
     
  10. Fostel

    Fostel Junior Member

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    Will this OEMTOOLS 22891 3/8 do the trick?

    or Magnetic Neiko 02292A 3/8 Inch?


    Thanks!
     
    #10 Fostel, Mar 31, 2019
    Last edited: Mar 31, 2019
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  11. Creliandobi

    Creliandobi New Member

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    A 5/8 will indeed fit down the well for the spark plugs -- I attempted to use a 5/8 spark plug socket this weekend, but to no avail as they needed a 9/16 for those I purchased.
     
  12. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    I see 9/16" converts to 14.2875 mm. I used 9/16", no problems, but if you're shopping and can find a 14 mm spark plug socket (has the rubber insert to grip the plug) that might be a preferable.
     
  13. lunacyworks

    lunacyworks Junior Member

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    Check the manufactures site, the thread is 14mm not socket size, the socket will be 9/16, [5/8] or 16mm but not 14mm.
     
  14. lunacyworks

    lunacyworks Junior Member

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    This is incorrect 14mm is thread! Not socket size. please remove this post to avoid future confusion.
     
  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    This is a G3 thread, not G2. My copy of the factory repair manual says 14 mm socket, for G3 Prius. The Denso website indicates the hex size is 14.3 mm for the SC20HR11 iridium spark plug.
    Denso.PNG G3 Spark Plug.PNG
     
    #15 Patrick Wong, Nov 17, 2019
    Last edited: Nov 17, 2019
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  16. iskoos

    iskoos Active Member

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    Wow... Seems all of the elderly threads are being resurrected due the Spark Plug socket size confusion:)

    I still stand behind what I have said and the correct socket size IS (MUST BE) 14mm, NOT 9/16"
    And with that said 9/16" should work since it is about 0.2mm bigger.
    If the 9/16" were to be the correct size, then 14mm would have NOT worked because it is smaller. I have a 14mm spark plug socket and it fits the OEM Denso plugs perfectly well (Snug fit, NO play). If it wouldn't have fit, then I would have agreed that the correct size was 9/16"

    So till someone explains to me how this is happening, I will continue to argue that the 14mm IS the correct size 9/16" being the substitute.

    And this is all for GEN3 Prius:)
     
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  17. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    There's a lunatic stirring things up too...
     
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  18. Grit

    Grit Senior Member

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    One person is only confused. Info here was correct.
     
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  19. iskoos

    iskoos Active Member

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    I hope this wasn't referring to me. Kind of rude...
     
  20. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Nonono: there's one feller with "lunatic" in is name, reviving every sparkplug thread going.
     
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