Broken spark plug in head procedure.

Discussion in '2005+ Mustang GT 4.6L Tech' started by KIMMER, Mar 9, 2009.

  1. Lime1Gt

    Lime1Gt Junior Member

    Dangerous:: If you've tried everything possible but removing the head; Don't know what the damage might be if this didn't work but do you think using the engines compression by starting the engine for a couple of seconds, would blow the broken porcelain and/or the electrode out of the spark plug hole? Then it would leave the shell to be removed. Just a thought, if the plugs electrode ground strap isn't broken. Just worried if engine vacuum might pull the porcelain into the cylinder.
  2. 07gts197

    07gts197 forum member

    I would forego that and just have the head removed. Its the safest bet. Though this thread is 3 months old so Im sure whatever has been done is done already.

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  3. Rick Simons

    Rick Simons Junior Member

    Just did mine two weeks ago. 122k with the original plugs, and they were definitely worn out; approx. .060-.070" gap. Used the cold engine method, though the warm engine method makes sense. Broke them loose and then went another 1/8 turn. Poured in PB Blaster up to the hex on the plug shell then let them sit overnight. The first seven came out fairly easily, but number 8 broke. Borrowed the removal tool kit from O'Reilly's and got #8 out without drama, just took another 1/2 day. Cleaned the threads and the lower holes with a cloth soaked in PB wrapped around a small round brush, then blew them drive with compressed air. Coated the lower shell and threads of the new plugs with nickel anti-seize. Good to go.
  4. scramblr

    scramblr Senior Member S197 Team Member


    Shouldn't put anti-seize on the threads and they may back out on you, jut the lower shell. If you leave them, just double check in a while to make sure they're still torqued down.
  5. 01yellerCobra

    01yellerCobra forum member

    I've used antisieze for years and never had anything I've used it on back out. That includes spark plugs, exhaust bolts, and suspension fasteners. My belief is that if its backing out it wasn't tightened properly and would have backed out anyway.
    dark steed likes this.
  6. Rick Simons

    Rick Simons Junior Member

    In my experience anti-sieze is a must on parts that heat cycle, especially when they're dissimilar metals. And I use a torque wrench on literally everything that I touch on this car.
  7. 1950StangJump$

    1950StangJump$ forum member

    Ford calls for nickel anti-seize on the bottom shaft, not the threads. Reason being, soot builds on that bottom shaft and seizes the plug to the head there. The procedure says nothing about using anti-seize on the threads, though I doubt its an issue if torqued to spec.

    I find it interesting how many people claim soaking the plugs in PB Blaster or similar before they attempted to uninstall helped them come out and avoid the infamous broken plug issue. The PB Blaster will never make it to that bottom shaft where the problem exists. If the problem was indeed the threads, that would be different, but it's not.
  8. msvela448

    msvela448 forum member

    Anything with threads does not stay tight just because of the friction of the threads. Bolts (and spark plugs) stay tight because of the proper amount of stretch which creates a clamping effect. Anti-seize will not affect a bolt's ability to stay tight if it is stretched properly. Anti-seize only prevents dissimilar metals, or metals in corrosive environments, from bonding.

    Connecting rod bolts, and cylinder head bolts are a primary example of where bolt stretch is critical. They are installed with lubricant (Moly or Oil) on the threads and under the bolt head / washer surface. The best way to determine if rod bolts are tightened properly is by measuring stretch, which may, or may not... match the recommended torque spec. If you can't measure stretch then torque is the next best thing.

    Tightening something by feel is the worst option... Over-torqued is half broke, and under-torqued is half loose.

    With regard to the old-style spark plugs on Ford 3V engines the seizing has very little to do with the threads. The extended piece of the spark plug has a thin gap between the shell of the plug electrode extension and the cylinder head. Because it's exposed to the combustion chamber it gets filled with carbon deposits that bind the bottom portion of the plug to the cylinder head. Combine this problem with the old two-piece spark plug design and they break in half when removing. Using a one-piece spark plug will really help with this problem. Anti - seize on the spark plug threads will have little effect on the problem.

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