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Thread: Another stuck glow plug thread

  1. #1
    Join Date
    Feb 2019
    Location
    Tucson
    Posts
    3

    Default Another stuck glow plug thread

    I've read through a bunch of threads on the forum, mostly about swollen tips. My old 1986 CUCV has its original plugs and my deal is that they don't want to unscrew at all. They look fragile and I'm afraid to snap them off. Any advice on how hard I should crank on them, or other tricks for getting them started?

  2. #2
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    Welcome aboard!

    You're right to be cautious. They can be easily twisted off, easier than a spark plug. It's easiest to remove them with the head off, but they can be removed in place. I highly recommend removing the injector on the cylinder you're working on. Plug the flash hole in the pre-cup to prevent anything from falling into the cylinder. The plugs are metal (obviously), but most have a porcelain core. Start by a liberal soaking of the threads with PB Blaster, repeated several times for days. You can also add some heat with a propane torch, heat-cycling several times, then trying removal once it isn't too hot. While it's very hot, you can try wicking the threads with a crayon, then let it cool before removal. If you twist one off, it'll have to be drilled then removed with an EZ Out. I like the spiral type for these. The square type can really cause a problem if you break one in the hole, usually requiring head and pre-cup removal.

    If you're able to thread them out, but they are swelled and won't pull out, remove the injector, plug the flash hole, break it off and push the tip back into the pre-cup. Use a shop vac at the injector hole, or high pressure shop air through the GP hole to remove the pieces. be careful to not blow the flash hole plug into the cylinder. I like to use a strip of inner tube, tightly rolled and twisted into the flash hole. They usually fit tight and stay put, and are easily removed when done. An added benefit is, if you forget them, they will burn off, harmlessly, once the engine is started.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
    Join Date
    Feb 2019
    Location
    Tucson
    Posts
    3

    Default

    Thanks for the help. Surprisingly, after just one night soaking in PB Blaster, the plugs are coming loose. I ordered the Kennedy Dieseling plugs for replacement, so will keep soaking the old ones until they arrive to loosen them up as much as possible. I haven't pulled any all the way out yet, so hopefully not too many will be swollen and hard to get out. If so, I see many threads on that topic.

  4. #4
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    It may not be that bad. When you get one out, check the part number on the plug. If it's anything but a AC/9G, or off brand (non-AC), chances are none will be swelled. A bit of soot buildup on the plugs can act like they're swelled. If they seem to stick coming out, spray some PB Blaster in the hole with the plug as loose as it can be (under the threads), then push, pull, twist, repeat until out. Clean the GP holes with a (gun) bore brush and some PB before installing new plugs. Use some anti-seize on the threads.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  5. #5
    Join Date
    Feb 2019
    Location
    Tucson
    Posts
    3

    Default

    Thanks for the advice. They all came out easily except one, which was slightly mushroomed. I almost gave up, but tried prying lightly with a screwdriver while unscrewing and it eventually walked out. Starts in one crank now.

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