spark plug leak??

Discussion in 'Engine, Fuel and Exhaust' started by Mavagrand, Nov 28, 2009.

  1. Mavagrand

    Mavagrand Senior Member

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    08 EGC stock. Noticed lately my front cyclinder plug is darker than the rear. Also there is a ring of oil/gas (not sure) around the base of the plug resting on the outisde of the cylinder right where the plug threads in. I have noticed this plug seems to have more "give" than the rear. By that I mean when I am tightening it down, it doesn't come to a clear definite stop but seems to always have a little play. I am afriad the threads are leaking...will this damage valves or anything??
     
  2. kemo

    kemo R.I.P

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    I would get a thread chaser and apply some lube to it and clean the threads out and then use some anti seize on the plug and try to tighted the plug. Could be that you have some carbon in the threads.
    kemo
     
  3. Drumrguy

    Drumrguy Account Removed

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    I would also let a professional look at it, that is a job where one thing leads to another and next thing you know, like smitty says, you are pulling the head off.
     
  4. RetiredJake

    RetiredJake Junior Member

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    It could be as simple as the plug was never seated from original installation. I found this on my Dyna last week. While it was in for the starter work, the Tech felt it was loading up when idleing, so he checked the plugs, felt they were fouled and changed them. While I was doing the 15K service the next week, I found that the gasket/washer had never been compressed on the forward plug.
     
  5. 1fltri4me

    1fltri4me Member

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    It sounds like the thread is stripped/oversize.
    If you loosen up both plugs,is there more play in that thread compared to the other one when moved side to side?
    The most accurate way to check is to use a thread plug gage.These are used in machine shops to check threads.They have a go and no go thread specific to the thread size.
    If the thread is already oversize,retapping will not fix it.You will need to repair it with a thread insert.
     
  6. glider

    glider Veteran Member

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    The gaskets on the plugs should be replaced when removing and reinstalling the same plug but nobody does it. They are a crush gasket and once compressed the first time do not offer the same sealing properties as the original installation.If the plug was installed and properly torqued originally and then removed for any reason and reinstalled, it may be leaking at the gasket. I would try a new set of plugs installed properly and see what that gives you. Otherwise a further inspection of the thread area would be next.
     
  7. 1fltri4me

    1fltri4me Member

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    Are these available?Never seen them.
     
  8. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    The copper crush washers for spark plugs are usually carried by auto parts stores in bulk like NAPA and the like. And of course they are always included on new plugs. Generally most replace old plugs rather than bead blasting, filing the contacts and regapping like the old days.
     
  9. Mavagrand

    Mavagrand Senior Member

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    Threads were dirty. I earlier had a loose head pipe on that cylinder..it must have created carbon/crud that had gotten into the threads. I just sprayed a little carb cleaner onto the threads and hit them with a stiff tooth brush. Now the spark plug seats fine and tightens up like it should. thanx for the advise, all.
     
  10. fwcole

    fwcole Active Member

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    i agree try a new set of plugs if that doesnt work, take it in.