Under the Volvo

"functionoverfashion" (functionoverfashion)
11/28/2017 at 13:41 • Filed to: None

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.

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.

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.

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.

DISCUSSION (7)

Nibby > functionoverfashion
11/28/2017 at 13:44

buy a new volvo wagon

functionoverfashion > Nibby
11/28/2017 at 13:47

Haha, oh man I’d love a new V90. Actually, I’d get the last of the previous generation because more space - the whole reason we got a Volvo wagon when we already had a 3-series wagon and an X3.

Ash78, voting early and often > functionoverfashion
11/28/2017 at 13:58

Europeans and their fancy-ass underbody fasteners. There have to be entire factories dedicated to finding how many different ways they can build the most complex, flimsy, expensive little bits for doing very simple tasks.

functionoverfashion > Ash78, voting early and often
11/28/2017 at 14:08

Seriously, you could write a whole post about a fictitious engineer at such a place, who gets fired for coming up with stainless u-nuts.

In case you were wondering, that’s what I’ve been using under my other cars for years, to replace rusty u-clips made of metal the thickness of cardstock paper and about the same fitness for purpose. And (don’t tell Mother Germany) I’ve been using ( gasp!) SAE 1/4-20 thread size!

Ash78, voting early and often > functionoverfashion
11/28/2017 at 14:16

I consider cross-threading to be a form of exercise!

At the moment, I’m back to zip ties on the Passat, which is missing 4 of its 12 underbelly fasteners (3 different varieties). You have to remove it for everything. It didn’t seem like a PITA back when I wrenched for fun, but once you’re doing it as a chore, it’s maddening.

functionoverfashion > Ash78, voting early and often
11/28/2017 at 14:35

Crossfit isn’t the same as crossthreading? I have a lot to learn, it seems.

The same is true on my car, I need 3 tools to get the shield off to do an oil change. Only 2 actual tools are required for the job itself. Plus I’m guaranteed to get sand in my face while trying to get the thing off, or back on. My wife’s car has a handy plastic access panel that comes right off for the oil drain. YAY

Ash78, voting early and often > functionoverfashion
11/28/2017 at 16:05

Remove 21, 15, and 9 fasteners for time.

Now AMRAP drain and fill the tranny, 20 minutes.