A few screws under the hood of my car need replacing. What's the best way to get replacements?

August 12, 2012 12:01 PM

The head of a screw under the hood of my car (in this instance, it's the one that attaches the mass airflow sensor to something) is stripped. It's a screw with hexagonal head which can fit a standard phillips head screwdriver. I'm going to get it out, but when I replace the sensor I can't put it back with the stripped screw, I'll need a new one. Is there some standard way to replace these screws with similar ones without going to the manufacturer of my car?

I see a few random assortments on Amazon, but in my searching I saw some people in car forums say that the screws in these are predominantly for wood, and for cars you want a "grade 5" screw or better.

How do people (like say, at your local mechanic shop) replace these screws? Do you just measure it and then go looking for something similar at Home Depot or a car parts place?

Are car screws called a specific thing? Are they kind of sort of standardized? Sit back, relax, and tell me everything you know about car screws.

Apologies in advance for asking the most boring question ever.

posted by Feel the beat of the rhythm of the night to Travel & Transportation (14 answers total)

Telling us the type of car, or maybe a picture may help.

I would try an auto-parts store first: shucks, auto zone, etc. If they don't have it, they can point you in the right direction.

Second I would try the dealer. They should be able to get you anything you want.

Third you can try the bone yards (or a u-wrench-it type place). Call around and ask them if they have your car there.

Fourth: eBay.
posted by jeffamaphone at 12:11 PM on August 12, 2012

My guess is that it isn't the screw that's damaged, but the plastic it's screwed into. If that's the case then a new screw won't fix your problem. Screwing into plastic (disregard if that isn't what you're dealing with) doesn't require a particularly high-grade screw. If the plastic is stripped then I'd just get a phillips head sheet metal screw, preferably stainless, that's one size up from the old screw.

(Yes, a screw nominally designed for sheet metal will work just fine in plastic.)
posted by jon1270 at 12:12 PM on August 12, 2012

Sorry, should have said that a new screw *of the same size* won't fix your problem.
posted by jon1270 at 12:13 PM on August 12, 2012

The car parts store has a rack with little semi-specialty screws (they're not that special, but they'll have a little flanged head or something) and they'll have one that matches. Failing that, go by your local dealer for your manufacturer and they'll be able to sell you one in a hot minute.
posted by ftm at 12:15 PM on August 12, 2012

Oh, and I misread your question. Since it's the head that's stripped, a replacement of the same type would be fine. Still, it's probably not necessary to match it exactly. So long as the length and thread pitch are right, you should be fine with a screw from the local hardware store.
posted by jon1270 at 12:16 PM on August 12, 2012

Seconding a junk yard.
posted by Blazecock Pileon at 12:22 PM on August 12, 2012

Any good hardware store or auto parts store (not a small and crappy auto parts store; one of the big ones with big racks of screws and nuts) should have a matching screw. Just bring in the old one and match the length and pitch. It doesn't matter if the new one has a phillips head, hex head, or whatever, as long as it screws happily into the same hole. As mentioned above, stainless is better because it won't rust.
posted by Forktine at 12:28 PM on August 12, 2012 [1 favorite]

I would suggest going to a mom-and-pop hardware store with the screw in hand. I have a shop around the corner from my house and not only do they have about a million different types of screws, they will sell you just one screw.

You could also try a specialty fastener store, we have some in the Cincinnati area called, Fastenal.

Like jon1270 said, if the size and thread pitch match, you should be fine. Especially if it's just a fastening screw and not some kind of specialty part.
posted by ThaBombShelterSmith at 12:54 PM on August 12, 2012

Is it the phillips slot that's stripped, or is the hexagonal shape rounded off? If it's just the slot, you should be able to get it out with a socket driver, and you can probably put the same screw back in with the socket driver.
posted by sageleaf at 1:32 PM on August 12, 2012

2nding taking it to a hardware store. It's pretty easy to match sizes and threads when you hold two screws up against each other.
posted by hydrophonic at 3:05 PM on August 12, 2012

Best answer: 3rding (4thing?) a hardware store or auto parts store with a big selection. Too see what's possible in the world of screws go to McMaster-Carr and search for "screws".

Also 2nding everything jon1270 said.

In this application the grade probably doesn't matter.
I expect mechanics get screws from the dealer, a local parts store like NAPA, or they have a stock of the more common ones.
The threading on car screws follow recognized standards like metric or SAE for machine screws so if you just need an M4 x 16MM machine screw (for a threaded metal hole) you can go to the parts store and get one.
If the screw threads in to plastic then you'll want a self-tapping screw, like a sheet metal screw.
Some automotive applications use special screws, but it's not the thread that's special, it's often the head size or it has a shoulder (unthreaded section below the head) of a specific diameter or length. In certain cases the screw or bolt head may have an anti-rotation bracket welded on and for that you should replace it with one from the manufacturer.
posted by highway40 at 6:23 PM on August 12, 2012 [1 favorite]

There are hardware stores and... hunt for an old established store that has a couple old guys and racks and boxes and nooks and crannies of stuff.
posted by sammyo at 7:28 PM on August 12, 2012

McMaster Carr is great. I haven't used it for perhaps two years, so it may have changed in the interim, but their website used to use filters that really worked and made sense to help you find the part you need.
posted by samofidelis at 8:33 PM on August 12, 2012

In this relatively non-mission-critical situation, you just need to find whatever screw is going to fit in the hole and hold the cover on.

Grade/thread pitch/head type are fairly unimportant here.
posted by davey_darling at 7:13 AM on August 13, 2012