Rusted Nut Problem Looking for a Solution

The Kia Sedona is nicely outfitted with a series of 6 threaded holes in the rear frame rails for the mounting of a trailer hitch. Trouble is, the threads rusted out of existence long ago.  The frame rails are boxed, so there is no access to them unless I remove the bumper, which is...

Option #1. Drill the holes larger, feed a new nut in above the existing nut, and use slightly longer bolts to secure. 

Option #2 is to drill and re-tap the holes slightly larger,  or drill then use an insert

Option #3 is to use some sort of self-tapping larger bolt. 

What thinks the hive? 

Go #2 on your Kia.

If you take a standard grade 2 bolt in the correct threads and file two grooves in the thread you've just made a thread chaser.  If it doesn't work, the softer bolt won't f-up the nuts.

You can drill and do a threadsert or helicoil

Find someone with a thread chaser.

Lube it up and go for it.  The worst that will happen is you mess up the nuts... but they're already messed up.

I have a thread chaser, but it was a no go because the threads are too far gone.  I think I will try the correct M12 tap and failing that, I will go to a 1/2" tap and use a slightly larger bolt. 

If the threads really are gone to the point where you cant chase them, then why not drill the bore smooth and see how close you are to the next tap size. Adjust accordingly. I am assuming there is enough metal in the captive nut to handle a slight increase in bolt diameter.

If I was fixated on keeping the existing hardware dimensions, I would be doing the drill smooth thing and then follow up with drill and tap new holes down the middle of the filled captive nuts.

Pete

i dont know how comfortable i would be redrilling M12 to 1/2"  At the very least I would go UNF instead of UNC because of the larger root diameter.  Do you have room to go 9/16?

Question -

Option #1. Drill the holes larger, feed a new nut in above the existing nut, and use slightly longer bolts to secure.

How are you going to feed in new nut?

93gsxturbo said:

i dont know how comfortable i would be redrilling M12 to 1/2" 

I had an RX-7 with a couple M14 lug bolts after one of the rear axles stripped.

I tapped the 12-1.5 threads first to 1/2-20, and then tapped those out to 14-1.5.  No drilling.

It worked and I got my wheels back on.

You would probably be fine drill/tap but when the accident investigation points to the standard bolts that Hillbilly Harold rammed into his ferrin car holding the trailer hitch on when it broke free and careened into a school bus full of children -- well, I wouldnt want to be Hillbilly Harold.

I did this on both of my odysseys. Get a metal spinny cleaner thing (looks like a pipe cleaner but metal) for your drill and go to town first before thread chasing. It takes forever but it worked for me twice.

https://www.amazon.com/gp/aw/d/B076F98493?psc=1&ref=ppx_pop_mob_b_asin_title

I was lucky enough in two cases ('06 RAV and my FIL's '12 Tacoma) to be able to carefully use a tap and cutting oil to clean out the threaded holes for the hitch. I think I installed the RAV4's hitch when it was 9 years old and my FIL's hitch when his Tacoma was 7 years old.

Unfortunately, it sounds like yours is a little past that. I'd still try to the tap in the standard size as a first step to see if the threads clean up any.

UPDATE: With a tap and a thread chaser, I was able to clean up the M12 holes and thread in bolts. I mounted the hitch and it looked good, but when I tried to torque the bolts to spec each one popped. That means that while I could get a bolt in, there just wasn't enough thread left. So, next is an attempt to enlarge the holes with fresh threads, or pass through with new bolts. 

Valiant first attempt!  Bring on round two!

I would look at bolt sizes that are close but a bit over what you have, then check out the tap-drill size for that thread and run that up the hole. Then tap and pray.

Do you have a welder or a friend with one? Easy enough to fill the wallered hole with weld and drill- tap to factory specs.

Pete

UPDATE: With a tap and a thread chaser, I was able to clean up the M12 holes and thread in bolts. I mounted the hitch and it looked good, but when I tried to torque the bolts to spec each one popped. That means that while I could get a bolt in, there just wasn't enough thread left. So, next is an attempt to enlarge the holes with fresh threads, or pass through with new bolts. 

I thumbs-upped your post because in consolation for failure you included a picture of a sweet minivan.