Replacing broken captive nut

[Grrrrrrr!]

So today I figured out why the previous owner had gas-axed a hole into the chassis rail.. they managed to break the captive nut for the front lower control arm off the inside of the chassis rail. Just wondering what approaches others have used to fixing this sort of problem. I've got a nut of the right thread, and access to a mig welder, but its not looking like i'll be able to the end of the mig torch in the hole to do a full weld.

Was thinking i could weld a decent washer to the end of the nut to spread the load, and just put a decent tack on the side I can get to to resist the torque when the bolt is tightened/loosened.

Other obvious option would be to cut more of the chassis rail away to get at it then replace that section of chassis rail. However thats going to look more "structural" than just a flat plate over the hole, and its going to be a lot more work in fabricating a section to fit.

Suggestions?

[Crucible]

Other obvious option would be to cut more of the chassis rail away to get at it then replace that section of chassis rail. However thats going to look more "structural" than just a flat plate over the hole, and its going to be a lot more work in fabricating a section to fit.

Suggestions?

That is really the only way. You can cut a section out very clean with a cut off wheel, then use the bit youve cut out as a template on new section and butt weld into place. Flap wheel on a grinder does a very good job of blending out weld beads, you cant even tell it has been welded. Of course make sure the bolt will start before welding in fully.

Spray some body sealer over aswell.

[metric]

Other obvious option would be to cut more of the chassis rail away to get at it then replace that section of chassis rail. However thats going to look more "structural" than just a flat plate over the hole, and its going to be a lot more work in fabricating a section to fit.

Suggestions?

That is really the only way. You can cut a section out very clean with a cut off wheel, then use the bit youve cut out as a template on new section and butt weld into place. Flap wheel on a grinder does a very good job of blending out weld beads, you cant even tell it has been welded. Of course make sure the bolt will start before welding in fully.

Spray some body sealer over aswell.

This

Cut the section out and replace, if the nut is on that piece weld it out first before welding back in the the rail.

[rollaholic]

is there access to the inner of the rail somewhere? i have seen some fitment kits for aftermarket stuff where the nut is welded to a large square washer which butts against the inner sides of the rail with a long piece of rod on it so you can push it down the rail to the appropriate place

[Grrrrrrr!]

Don't think there is much in the way of access to the inside of the rail, hence why the prev owner gas-axed it. Will have to investigate when i get home tonight. Flap disc method of smoothing the welds isn't likely, there is little access with other parts of the suspension mounts getting in the way. Might see about borrowing a battery grinder and seeing if there is a donor car at pick-a-part/zebra.

[evil_si]

Rivnut?

[Grrrrrrr!]

Have you got a m12 x1.25 rivnut good for a bolt thats supposed to be tightened to 118 Nm ?

Managed to open the hole out a bit with a powerfile, welded a HT nut to a big flat washer then put a fairly healthy tack on it all to hold it in place. Just finished bolting the suspension back in, and gave the main bolt a few tighten and loosening cycles to see if it'll hold, looks good, so now I can plate over the hole and get me a WOF. Hopefully I dont have to do that again, its a prick of a job when you are welding under a car on short axle stands. Wish I'd done it at work, could've picked the car up with the crane and worked at a convenient height.