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December 24, 2012 10:11 AM

Can I fix this seat belt by myself?

A friend was putting on the seat belt in the passenger seat of my 2004 Nissan Sentra and this piece came out of this hole. The hole is below and slightly behind the car seat, on the wall. I've done some googling and have not been able to find much information about an issue like this, mainly because the "belt" responses I'm getting have more to do with serpentines than seats. It looks to me like I can just screw it back in, but I wanted to get another opinion before I did something potentially dangerous with a seat belt.

posted by sacrifix to travel & transportation (16 answers total)

It may have gradually unscrewed or it may be stripped. When you screw it back in, how sturdy is it?
posted by DoubleLune at 10:16 AM on December 24, 2012

Screw it back in. Check it in a week. If it loosens, put some thread lock on it.
posted by sanka at 10:21 AM on December 24, 2012

Pretty much what DoubleLune said -- it's a one minute fix if the threads in the hole aren't stripped. If they are stripped, it's harder, as the threads are part of a flange that's welded to the back of your car's body, meaning you'd have to drill them out or grind them off, then use a high quality nut (metric grade 10.9, say) and large fender washer to secure the bolt.

Screw it back in. Check it in a week. If it loosens, put some thread lock on it.

That's good advice for everything except seat belt bolts. They HAVE to hold secure, or they aren't worth a damn. It isn't enough to hold them with threadlocker and some wishful thinking; those suckers need to hold.
posted by mosk at 10:25 AM on December 24, 2012

It seems sturdy enough when I screw it back in but I know my yanking is nothing compared to even a minor car accident. How do I tell if it is stripped?
posted by sacrifix at 10:28 AM on December 24, 2012

Maybe you should take it to a mechanic. If nothing is wrong, it will be super cheap. If something IS wrong, you'll be glad you took it in.

Also, those bolts just don't loosen and fall out for no reason. Either this was a really serious assembly defect when the car was made, or something is broken.
posted by ryanrs at 10:33 AM on December 24, 2012 [3 favorites]

How do I tell if it is stripped?

That bolt has a torque spec, meaning that the factory service manual states exactly how much force should be used to tighten that bolt. This tightening is done with a torque wrench, a special wrench that measures, well, torque (twisting force), and if the threads won't hold, the wrench won't register the full torque value specified for that bolt.

This is something that any decent mechanic can do, including shade tree mechanics, provided they know the proper torque specified for that bolt. You may be able to find that spec online.

UPDATE: The factory service manual can be downloaded here.
posted by mosk at 10:39 AM on December 24, 2012

OK, from the SB section of the above linked factory service manual, here's a screenshot of the seat belt bolt torque spec:

Image

This bolt should be torqued to 43-55 newton meters or 34-40 foot pounds, depending on whether your mechanics use metric or Imperial measurements.
posted by mosk at 11:00 AM on December 24, 2012 [1 favorite]

It's meant to be unscrewed/re-screwed, in order to do things like gut the interior.
posted by Thorzdad at 11:01 AM on December 24, 2012

What mosk said. You don't want to just tighten this bolt, you want to tighten it to spec. But if I were you I would find out why this bolt came undone or was never done. The dealership should be tripping over themselves to fix this if it came undone on its own, because that's a huge effing potential lawsuit if someone were in an accident and that bolt wasn't secure due to manufacturer error.
posted by zippy at 11:13 AM on December 24, 2012 [2 favorites]

An easy way to tell if a bolt is stripped is if it wont tighten. If you can lean on the wrench and the bolt dosn't give any, it ain't stripped. Stripped bolts happen when either the thread on the bolt or the nut (in this case the nut is welded to the flange-the bit on on the second picture) is removed and there isn't enough metal left to securely hold things. This is usualy caused by cross threading, which is really, really hard to do on a large coarse threaded bolt. The bolt in this case has the little bit on the tip that isn't threaded and that is there to make stripping it even harder (because, well its a seatbelt anchor and that matters) and the bolt nor nut looks stripped to me. Stripped bolts are also harder to turn, so if it starts easy and goes in a turn or two by hand before you need to use a wrench on it and then tightens up without just spinning in the hole you are good. And I have never had one of these bolts back out, i bet either at the factory or at some repair (ever had the carpet or seats replaced or worked on?) someone didn't tighten it up with a wrench and only hand torqued it. Check all the other seat belt bolts while you are at it.
posted by bartonlong at 11:17 AM on December 24, 2012

The bolt in this case has the little bit on the tip that isn't threaded and that is there to make stripping it even harder...

This feature on a bolt is called a 'Dog Point'.
posted by Confess, Fletch at 11:50 AM on December 24, 2012

It's bizarre that this bolt came loose; bartonlong's suggestion that the bolt was removed at some point and not properly reinstalled is possible.

At any rate whatever the cause if properly torqued with low strength thread locker the bolt shouldn't come back out.

Note that the bolt is mostly loaded in shear in an accident.
posted by Mitheral at 12:44 PM on December 24, 2012 [1 favorite]

thankyou confess, fletch. That is a really useful site
posted by bartonlong at 3:17 PM on December 24, 2012

Take it back to a dealer and indicate the screw fell out. I believe there are special warranty conditions around safety equipment so this might be free or low cost. (Check your owner's manual)

If not I would indicate to them that you believe there are special warranty conditions around safety equipment and isn't it lucky that you discovered the problem and it wasn't found in a major accident. If they still don't budge on the price ask for a phone number of a regional manager.

It really is in their best interest to have this fixed correctly - especially since it's probably a quick fix for them...
posted by NoDef at 10:52 AM on December 25, 2012

Here is an excerpt from a 2012 Nissan manual:

SEAT BELT LIMITED WARRANTY

WHAT IS COVERED AND FOR HOW
LONG
This warranty covers any Nissan supplied seat belt or
related component, that fails to function properly during
normal use within ten (10) years of the date the vehicle
is delivered to the first retail buyer or put into service,
whichever is earlier.Warranty repairs are free of charge
for parts and labor.

I'm assuming the 2004 warranty wasn't much different - so you are probably still within the warranty period. Don't fool around just let them fix it...
posted by NoDef at 10:56 AM on December 25, 2012

I borrowed a torque wrench from the local auto parts store and (with the help of YouTube) got the bolt back in to the correct tightness. I can think of two occasions where the seat belt may have been unscrewed and not properly re-set and the bolt was not stripped so I am pretty sure it wasn't a failure of some kind. Thanks everyone for your input!
posted by sacrifix at 12:43 PM on December 25, 2012