What screw do I use, and where do I get it?

July 4, 2009 7:42 AM

While changing the lightbulb in the front turn signal on my car (a 2003 BMW 330i), I managed to lose the screw that connects the turn signal assembly to the car. What kind of screw can I get to replace it?

I imagine there must be some standard size to use, but if so, I haven't been able to find it. Assuming I can just buy a garden-variety phillips-head screw, what's the specified size?

I've been trying to find the reference to the original part, on the RealOEM site and elsewhere, but while I can find the page for the signal assembly and various pages for mounting parts, I can't seem to find the entry for the particular screw that I need.

posted by Zonker to travel & transportation (12 answers total)

Is it too much trouble to remove the same screw from the opposite side turn signal and take it to the home center for a perfect match?
posted by dinger at 8:08 AM on July 4, 2009 [2 favorites]

The easiest thing to do is just grab the screw from the other side, take it to a Lowes or Home Depot and get a fastener that with the same thread pitch.
You probably won't be able to order the screw individually from BMW. When you order a new light assembly, they count on you to save the original hardware. New fasteners aren't generally provided unless they're a one-time use (torque to yield) or they're very critical (like a large subframe bolt). And those fasteners don't come individually, either. If I order an axle, a fresh bolt will come in the box and the contents of that box are covered by a single part number.
You could try taking it to a BMW parts counter and they might have some loose stock in bins. But I know our parts catalogue doesn't list hardware.

Where did you lose the screw? Did it fall down into the abyss of the car? Most new cars have a big plastic belly pan. Lay down and smack the pan and you'll be able to hear the screw rattling around. You can typically smack the pan until the screw emerges. A small telescoping magnet (available at any Pep Boys or similar) is one of the most useful things you can own, when engaging in any car repair.
posted by Jon-o at 8:12 AM on July 4, 2009

I hate that problem, especially with fancy-ass products that insist on using unusual screws.

If you go hunting for a match, remember that it's probably a common metric size, which you can certainly get at Lowes or Home Depot, but it's a different section. I'd take the (opposite side) screw in to any European auto parts store myself, BMW or otherwise, and let them find a match in the back.

In desperate straits, I've often resorted to a skinnier bolt with nut. If you can reach the other side (for the nut) you can usually tighten this hack enough to do the same thing the screw was doing, even if it's not using the threads in the screw-hole and is technically the wrong size.
posted by rokusan at 8:16 AM on July 4, 2009

I'm a little leery of removing the opposite screw since it would be easy to lose that one, too (it's in a location where it's fairly hard to grasp). The belly pan idea is a good one, I'll try that and a few other efforts to find the lost one.
posted by Zonker at 8:19 AM on July 4, 2009

It will be metric. Why don't you go to/phone the BMW dealer? They'll find one in two minutes. You realize it will be just as easy to lose the new one when installing it, right? So take the other screw out a couple of turns, then knot a long thread around it so when it falls you can retrieve it. You can do the same thing in reverse when putting it back.
posted by weapons-grade pandemonium at 8:30 AM on July 4, 2009

it's in a location where it's fairly hard to grasp
Welcome to working on German cars!
That string idea sounds great. A plastic zip-tie might be easier to implement in a space where it's harder to fit your hand. A magnet, or magnetic screwdriver will work for you too. You can also put a rag under the screw, blocking any gap or abyss that the screw might disappear into.
Don't be afraid to take apart the other side, dude. That bulb is going to blow some time and you'll have to take it apart then anyway. Putting your fear aside is the best tool to have when working on your German auto!
posted by Jon-o at 9:03 AM on July 4, 2009

Blu tack on the end of your screwdriver is your friend when taking screw out (putting them in) in confined spaces.
posted by A189Nut at 9:44 AM on July 4, 2009

Magnetic screwdriver, take out the other side, get replacement screw and bulb for other side (since it's already taken apart), put everything back together. When you're done don't forget to thrust your hands skyward and yell..."these hands have been touched by God!"
posted by torquemaniac at 10:13 AM on July 4, 2009 [1 favorite]

If the screws are stainless steel, and they might be on a BMW, a magnet won't work.
posted by weapons-grade pandemonium at 12:13 PM on July 4, 2009

call a local dealer?
posted by fistynuts at 12:40 PM on July 4, 2009

If the screws are stainless steel, and they might be on a BMW, a magnet won't work.
Um, steel is ferrous. I think a magnet will work. There are other alloys (usually involving magnesium, alluminum, or whatever) in automotive applications that are non magnetic, but fasteners are usually something cheaper and magnetic. Also, only steel (stainless or otherwise) has threads that are any good. It's hard to find anything else in use, as far as common automotive fasteners goes. I can't recall ever encountering a screw or bolt that I can't pick up with a magnet, to tell you the truth.
posted by Jon-o at 8:18 PM on July 4, 2009

Found it in the belly pan, retrieved it with a hunk of duct tape on the end of a ruler. (Is there anything duct tape can't do?)
Thanks for all the responses.
posted by Zonker at 10:10 AM on July 9, 2009