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Front tow eye rusted threads

Discussion in 'Gen 2 Prius Technical Discussion' started by ChapmanF, Apr 17, 2008.

  1. ChapmanF

    ChapmanF Senior Member

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    My NHW11 came with a mint-condition tow eye in its little foam block in the trunk.

    But the tapped threads in the front bumper are so rusted that the eye can't even be started into the hole.

    If I'm ever in a ditch needing to be pulled out, I'm going to be sitting there saying "but. I. can't. get. this. eye. in. this. hole."

    I probably need to buy a tap the right size and run it through the hole, but 'the right size' is the trick. From trying to measure it, I'm guessing it's M21x2, but none of my local hardware or even auto shops has a thread gauge that big to really confirm it. I can mail order a tap but in those sizes they're not cheap, so I'd like to be right.

    Has anybody been down this road before? Is there by any chance a PriusChat official circulating "clean up your tow eye hole" tap? :)

    -Chap
     
    #1 ChapmanF, Apr 17, 2008
  2. tochatihu

    tochatihu Senior Member

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    I put grease and a wine cork in that hole early on, so I don't feel your pain. Can you not just read the thread pitch and diameter off the tow bolt? How about aggressive cleaning, then see if you can get the (oiled) tow bolt started in? Cross-cut the bolt threads with a hacksaw, and file off the first few? It should still grip enough with the deeper threads I guess. Anything to avoid buying that tap (which won't clean the last several threads anyway).
     
    #2 tochatihu, Apr 18, 2008
  3. seesfar

    seesfar New Member

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    You might try buying a 3/4" round wire brush and chucking into drill and running for a few minutes in bolt hole. Usually cleans OK.
     
    #3 seesfar, Apr 18, 2008
  4. jayman

    jayman Senior Member

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    +1, a Dremmel tool works fine too. Spray a lot of WD-40 onto the threads first, to help break up the loose corrosion. Give a 3-5 sec buzz with the brush, then use the WD-40 to spray out the crud.

    This process will have to be repeated a few times, so be patient. If the threads are real bad, a thread chaser or even a tap will be needed.

    Once the threads are cleaned, put a heavy dollup of grease in the hole
     
    #4 jayman, Apr 19, 2008
  5. Seamus

    Seamus Grumpy old man

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    Thanks for the tip. I opened mine and sure enough it had a lot of raw metal. I slobbered a lot of grease in there in case I ever need it.
     
    #5 Seamus, Apr 19, 2008
  6. tochatihu

    tochatihu Senior Member

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    Seamus, the 2001-2003 Prius is different because this bolt hole is open to water and road debris. I do not know how well the plastic cover works in the new model.
     
    #6 tochatihu, Apr 19, 2008
  7. Seamus

    Seamus Grumpy old man

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    Well the "cover" is really just a plug for the hole in the bumper cover. As I mentioned it looks like the threads are not corrosion protected.
     
    #7 Seamus, Apr 20, 2008
  8. ChapmanF

    ChapmanF Senior Member

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    Hmm, I see that I never followed up in this thread with the answer.

    The thread on the Gen 1 tow eye is M22x2, for which I ended up buying a bottoming tap to clean up the threads.

    Just for the record, I have a Gen 3 now, and my tap does not fit the Gen 3 threads. The Gen 3 eye has a smaller thread diameter (18mm maybe? I measure 17.66 across the threads) and a yuuge thread pitch (3 mm ?!). The thread profile on the Gen 3 looks like it might be something exotic, the threads are trapezoidal rather than triangular, reminds me of Acme threads. (And might even be Acme, the Wikipedia article says there's also a metric trapezoidal standard but it isn't more common than Acme.

    But all that's distraction if you have a Gen 1 ... plain, vanilla, M22x2 for Gen 1.

    -Chap
     
    #8 ChapmanF, Jul 18, 2016
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