I'm installing a trailer hitch to a 2005 Toyota Sienna. To install it you put some bolts through it into the underside of the carriage into what are apparently termed "weld nuts" in the frame.

Problem is, they are right by the tires and subject to...junk and crud and rust. And not protected.

I am having trouble cleaning them out so the bolt will screw in. Any suggestions?

Background video: https://www.youtube.com/watch?v=wj3V9Ga5_eU

Saw What do do with a rusted (not seized) nut but seems this condition is barely different since it's a particular type of nut (trailer rear hitch weld nut) in this case.


2 Answers 2


The best way would be to clean the thread using a tap.

If you don’t have the correct tap or cannot borrow one, then cut a slot in the threads of a spare bolt and work that in gently - removing the bolt and cleaning as you go. Plenty of cleaning fluid helps.

  • I was able to purchase a "single" tap and it worked great, thanks!
    – rogerdpack
    Commented May 8, 2020 at 22:56
  • 1
    @rogerdpack good for you, well done and it will cone in handy again.
    – Solar Mike
    Commented May 9, 2020 at 5:59

Most common advice: clean with a wire brush and WD-40. Wait 15 min. Repeat several times.

Once you can get a few threads in then "work" the bolt in as it gets farther in gradually, adding WD-40 each time, backing it out to remove some junk.

ex: https://www.youtube.com/watch?v=Eb0Mj5b0urY and and example of the "working" part again: https://www.youtube.com/watch?v=_K1fWUBw4pQ

When that doesn't work then a "thread cleaner/restorer/chaser/thread repairer" there seem to be a few incantations of those.

ex: https://youtu.be/AG3N_0xEwok?t=79

You can get a rental thread restorer set at auto parts stores.

Another option is to grind some grooves into one of your bolts to make it "into" a thread cleaner.

ex: https://youtu.be/AG3N_0xEwok?t=10

When that doesn't work then a thread tap. They have a tapered entry edge and work great. You can sometimes buy "single" taps of the right size from auto parts store.

If that doesn't seem to work, you can break the weld nuts (detach them) and add bolts and things from above, as a replacement, ex:


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