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Discussion Starter · #1 · (Edited)
Hello Everyone, I was replacing a 2008 Serpentine Belt Pulley Tensioner with a new OEM one from Honda. (Part #: 31170-r70-a01)

The old one's bolt broke off and I was happy to extract it earlier today without any issues and was hoping everything would be smooth sailing from there on but when I went to put the new one on it would not tighten in and was loose and wobbly.

I noticed the old one (I don't believe an OEM part) had a Larger Standard 1/2-20 bolt.
The new one has a Smaller Metric 12 x 1.25 mm.

Tomorrow I will run back to the Honda Part's store (or try Lowes) to see if they have a Standard 1/2-20 bolt. I'm hoping this will fit more snug and proper.
I'm hoping the Standard 1/2-20 bolt that was in there before didn't damage/loosen the threads because I believe it is supposed to be the Smaller Metric 12 x 1.25 mm.

Has anyone run into this issue before or have any advice? I'm hoping I don't have to re-tap the threads or anything like that (I've never done that before).

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Discussion Starter · #7 ·
Hello Everyone, thanks again for taking the time to respond!

So, I think marvinstockman is correct in that the person who worked on this Odyssey before may have tapped the hole for 1/2-20.
I found a grade 8 1/2-20 at my local mom and pop hardware store (after an unsuccessful visit to Lowes).

I just tested it out and was able to hand tighten the new 1/2-20 all the way in to test it.
The new bolt fits "fairly" snug.... there is the slightest wobble/shake when I try and move the bolt back and forth.

So the question now is:
  • is that very slight wobble normal or should it not move at all?
  • Would lock-tight work at all (even though the instructions recommend clean motor oil to lubricate).
  • Should I try re-tapping it again at 1/2-20 to see if that would tighten things up?
  • Or Maybe I will be ok using this new bolt with the slightest wobble or maybe I should definitely go the Heli coil kit route?
  • Would a lock washer on the bolt head instead of a flat washer help?
Thanks again everyone!
Ps. photo below of the new bolt... I'm assuming adding a washer wouldn't hurt.
Jamy

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Discussion Starter · #8 · (Edited)
You know what, after that whole write up above, IGNORE it....
I just found out that the 1/2-20 bolt doesn't fit through the new Drive Belt Auto-tensioner!!!

So I think I will have to "use a Heli coil kit to re-thread it to OEM spec and use the OEM bolt" @ 12 x 1.25 mm

The question now is that it appears that for the Heli Coil kit I need a 31/64" drill bit... I'm just not sure if the existing hole for the 1/2-20 bolt is already larger than that?
 

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Discussion Starter · #11 ·
Thanks @thscott and @nitely2! I'm not 100% sure if that old part was drilled to fit the 1/2" bolt but I am considering your suggestion of enlarging the hole in the new tensioner because I've never done a Heli-coil before and my work space is limited and it may be a challenge to get everything aligned properly.

My dry run of the new 1/2-20 bolt seemed ok... but did "give" a very tiny bit and had a very slight wobble if I pulled back and forth on the bolt so I am trying to consider if that is good enough to hold the pulley in place after going through all this work. (Boy, I wasn't expecting this extra challenge!)
 

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Discussion Starter · #15 ·
@hpark21, I believe so.
@nitely2, I do like that idea of drilling the hole through and putting a longer bolt with lock washer and nut if there is room to do that, that is pretty creative, thx.


Thanks @thscott and @nitely2! I'm not 100% sure if that old part was drilled to fit the 1/2" bolt but I am considering your suggestion of enlarging the hole in the new tensioner because I've never done a Heli-coil before and my work space is limited and it may be a challenge to get everything aligned properly.

My dry run of the new 1/2-20 bolt seemed ok... but did "give" a very tiny bit and had a very slight wobble if I pulled back and forth on the bolt so I am trying to consider if that is good enough to hold the pulley in place after going through all this work. (Boy, I wasn't expecting this extra challenge!)
Actually, the more of I think about it, this may be the best solution at the moment?
Has anyone every had success with this type of thread sealant or threadlocker to help with a bolt that may wobble or give just a little bit?

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