My friend worked on my car to replace the exhaust manifold/cat converter gasket and I noticed rattling noise as if something was loose. Checking with my a bore-scope camera with my phone, I saw the flange nut being put the wrongway in the manifold stud and to make matters worse, it is in a deep hole so I can't get any tools in. enter image description here

The manifold nuts that is stuck looks like this

enter image description here

the location where the bolt is stuck is circled in red

enter image description here

Would anyone have any tricks or idea as to how to remove this. Thanks

  • Is this on a stud or a bolt? If a bolt, can you get to the other end (bolt head)? Commented Sep 10, 2022 at 20:21
  • @Pᴀᴜʟsᴛᴇʀ2, It is a stude. The flange nut is threaded wrong way on a stud.
    – ShanjayG
    Commented Sep 10, 2022 at 20:25
  • I wonder how he managed to put that nut on? Even locating it on the stud would have been difficult, not being able to put it in a socket.
    – HandyHowie
    Commented Sep 11, 2022 at 7:29
  • how deep is the hole, exactly? Too deep for needle nose pliers? Commented Sep 13, 2022 at 16:40
  • @SortofDamocles , Yes, pliers are too short, even if the pliers were long, don't think there is enough room for it to open wide to grab the top and bottom part of the flange nut.
    – ShanjayG
    Commented Sep 14, 2022 at 16:16

4 Answers 4


Here is my suggestion:

Find another flange nut which is the same type, a flange nut with the "grippers" (don't know what else to call them) on it. Drill out the threads just enough so it won't catch on the threads of the stud. Then put a little bit of electrical tape on the hex portion of it so it will stick in your socket. Next, use some carb cleaner or something and clean the flange side of the stuck nut. Then put your modified nut down on top of it (flange side first, of course). While putting downward pressure on the whole get up, slowly try to loosen the nut which is upside down. The grippers from both flange nuts should counter each other and grab, making it so you can take the upside down one out.


I had an idea of using a 12pt socket that is a tiny bit smaller than the flange, put on extension, hammer on, then unbolt. I did not have a flange nut to test, so tried with a nut and washer which is not exactly the same, I know. The washer bent over and gripped the socket. I had to hammer it out enter image description here

  • Definitely worth a try. May work if the socket is just the right size.
    – HandyHowie
    Commented Sep 11, 2022 at 19:48

There do exist specialty pliers for this sort of situation, if you are able and willing to buy a new tool for the job. See for example: link to ACE hardware


I'd get some soft metal (aluminum?) tubing that has an "interference fit" on the flange, hammer it down (so it grips the nut) and use pliers to unscrew it.

Fabricating such "helpers" is one of the reasons why shops often have a lathe around.

Even some fitting plastic tubing could work if the nut isn't seized (then perhaps even a fitting rubber hose).

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