The plastic underbody shield on our 2012 Volvo XC70 is hanging down, near the rear wheel on the driver’s side. It seems to be held up by these cheesy little nuts that thread onto small, rough-threaded studs that protrude from the unibody. In just five years, the rust is bad enough that the nuts either come apart on disassembly, or the studs’ threads are gone, or both. So now I have to find a new way to fasten the shield.

WTF is this piece of rusty garbage you call a fastener? There’s more steel in a box of Wheaties than in that nut.

I zip tied it in another place at first, of course, but it rattles and wears through the zip tie over time. The other night I couldn’t stand it anymore and I drilled out a tiny block of mahogany and kind of jammed/threaded it on to the stud as a temporary fix. Amazingly, it’s been there for more than 2 weeks and probably 500 miles. But I need a real solution.

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pictured: how NOT to replace a fastener. On the other hand, this will never rust!

I can’t handle the heckling I’d get from my local shop if I brought in the car with mahogany nuts holding up the shield.

the upside-down crater in the plastic near the edge is the hole where the fastener lives, up a few inches from the bottom of the shield.

I thought about a self-tapping screw, provided that it’s short enough not to puncture anything inside the car, like the gas tank, which is likely to be in that neighborhood.

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Of course, after locating this little gem (with a built-in little gasket) at the hardware store, I decided that I would be better off drilling a very shallow hole with a drill bit, then putting in a screw that doesn’t have an extra-long tip for no reason except ease of installation. Hindsight, etc.

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I’d try to put a thread on the stud, smaller than whatever was there, like a #8 / 32 or something, but I don’t think I can really get a die in there. I could just force a small stainless nut on over the rust - between the softness of the stainless and the rusty part, I’m sure it would work. But taking it on and off multiple times successfully? Probably not.

What else can I do here, oppo? There are already two of these that I need to replace, and I’m sure more in the future.