Why did my car window explode?
January 29, 2009 7:12 PM   Subscribe

This evening, I got home from work and came inside. About twenty minutes later, my daughter came in from playing in the backyard, crying, and told me that my car window had broken. When I went out, it became clear that the window had burst from the inside--the bits of glass still attached were bowed outward, and 80% of the fallen glass was in the driveway. What on earth happened?

More information, maybe relevant.
  • The car in question is a 2004 Saturn.
  • The car was locked, and there weren't any--you know, huge, window-breaking birds inside of it.
  • The window had no scratches, nor had it been hit by anything. (Either when it burst or before this.) The car has never been in an accident, either.
  • We'd used the car to get home from work in, and the heat had been on, but it was definitely not hot in the car. We were chilly, even with our jackets on.
  • The temperature outside was in the low to mid twenties.
  • The bursting happened about twenty minutes after we got home.
My daughter said that she heard a boom, and then the window broke. (The backyard is right next to the driveway.) My neighbor, who came outside when he heard her yell and got there before I did, said that she was still in the yard when he came outside--and really, even if she weren't, she's six--there's no way that she could break my car window.

Again, from everything that I could see, the window literally exploded, bursting outward. There were no objects in or near the car that could have hurt the window (a few pieces of junk mail and a kindergarten art project were in the front seat), so no chunks of ice sliding off the roof or anything.

How could this happen? The best I can come up with is some mumbled mumbo-jumbo about air pressure and heat, but...well, but surely that's not it, because if it were, car windows would burst all winter long.

Further, what do I do now? Is there any chance that I could get the dealership to cover it, since as far as I can tell, this was some sort of defect in the window itself? I have a thousand dollars deductible on my insurance, and I figure that replacing a window will certainly be less than that--it's not even worth calling them, right? (Plus I fear that this would be seen as an "act of god", meaning that they wouldn't cover it anyhow.) I have a tarp over the window (closed into the door) in the meantime--is there anything else I should do to protect the interior of the car?
posted by meghanmiller to Travel & Transportation (31 answers total) 8 users marked this as a favorite
No idea. I once was waiting for the bus when a piece of glass in the bus shelter shattered for no apparent reason. Strange.
posted by DieHipsterDie at 7:18 PM on January 29, 2009

A broken spark plug casing will cause auto side window glass to explode violently. Maybe vandalism?

You say it appears that the window was broken from the inside, but really, how sure are you? If the glass fractured and fell into the car it still could have been broken from the outside.

A pebble thrown up by a passing car? A neighbor's pellet gun?
posted by wfrgms at 7:21 PM on January 29, 2009

Response by poster: Oh, possibly also worth mentioning is that the vast majority of the glass was knocked out of the window before I ever got outside--maybe 75-85% of the window was gone. The rest of the glass fell out when I closed the tarp into the door.
posted by meghanmiller at 7:22 PM on January 29, 2009

If your car, warm(ish) from the drive home, cooled off unevenly then perhaps some kind of torsion in the window frame cause the glass to twist and break? It might not have had to be particularly hot, just changing temperature faster on one side (or in one area) than another.
posted by onshi at 7:26 PM on January 29, 2009

Glass can have weird stresses frozen into it during manufacture (eg and eg). Maybe the window wasn't properly annealed, or some other manufacturing defect? Maybe some moisture/condensation got into the window frame and froze, causing it to crack? That's the only thing I can think of, but it's definitely in the mumbled mumbo-jumbo category.

Interesting that your daughter said she heard a boom and then the window broke. Could she see the window from where she was when it happened?
posted by hattifattener at 7:28 PM on January 29, 2009

Response by poster: Regarding the glass breaking from the inside, I'm almost 100% sure. There were a few small pieces of glass inside the car, but all of the large pieces and the vast majority of the glass were on the driveway. (And we're talking palm-sized pieces on the driveway, pinkie-fingernail-sized pieces in the car.)

The car was pulled up far along the side of our house. There's a picture of the driveway here--the car was pulled back roughly to where the Jeep in the far left of the picture is, so it couldn't have been anything from the road. There aren't neighbors behind us (it's a cemetary), and there's a high wooden fence separating us from the neighbors to the right--they'd have to be on their roof to make that shot, and they weren't home anyway.

I'm not trying to be argumentative, I'm just really confused.
posted by meghanmiller at 7:30 PM on January 29, 2009

Response by poster: Hattifattener--yes, she could see the window. Our driveway runs the length of our house and the length of half of the backyard, and the car was near the end of the driveway. She was in the backyard.

Unfortunately, that also mostly rules out that someone could have done something to the car, both because she would have seen them do it (she didn't come inside at all when we got home) and because there would have to be adult footprints in the snow on the passenger side of the car, and there weren't.
posted by meghanmiller at 7:33 PM on January 29, 2009

Best answer: If you Google for 'exploding car window' or 'car window exploded' you find a lot of similar reports, even blog posts and Flickr sets, from drivers of a variety of vehicles. It appears at least at first glance that a lot of people did get it covered by insurance. I would personally let the dealer know because if it was a flaw caused during manufacturing, others could be affected by it as well.

There are a bunch of reasons people give for why the glass could have spontaneously "exploded," such as a defect in the glass, uneven stresses on the window from the frame, a defect in a rear defogger and/or a defogger inadvertently left on. I don't know much about this so I can't vouch for the accuracy, but I found an interesting summary left by user Oberon in this message board thread.
posted by jeeves at 7:33 PM on January 29, 2009 [1 favorite]

I was walking out of a restaurant one hot summer day when this happened to a truck as I was walking past. The driver of the truck had just got in and had just started to roll the window down. The window shattered into ~1billion pieces. I was freaked out, and I was in High School when it happened!
posted by ArgentCorvid at 7:37 PM on January 29, 2009 [2 favorites]

There is a long string of incidents in which automotive safety glass has spontaneously blown out. Although this is the first time I've heard of a car window doing it. BMW/MINI sunroofs have been known to spontaneously blow out. There have been several threads on NAM about this, and in each case it was related to a manufacturing flaw. Gather evidence from car forums and go talk to your dealer - maybe GM will cover it. If not, your insurance will cover it.
posted by pandanom at 7:39 PM on January 29, 2009

Best answer: The side window of your car was probably tempered glass. Apparently this type of glass is known to spontaneously explode from time to time due to manufacturing defects. I guess you got lucky :)
posted by waxboy at 7:40 PM on January 29, 2009 [1 favorite]

Oh, and spontaneous glass breakage on Wikipedia.
posted by jeeves at 7:43 PM on January 29, 2009 [1 favorite]

Auto glass, except for the windshield, is tempered. It's heated and cooled in such a way that it develops compressive stresses throughout the piece. This makes the part much stronger.


The problem is the compression. As long as the surface in unharmed, it's fine -- but a small flaw can release the stress, and *bang*, the glass shatters. Moreover, it shatters into little bits, not giant sharp shard. These are the reason cars use them -- stronger, and safer when it fails.

I vividly remember watching a sunbeam hit a stack of flat temper glass for tabletops. It warmed one corner up quickly, and *BANG* -- it shattered, and then then entire stack shattered. About six grand of glass turned into chunks in less than a second. So, a minor flaw in the glass, a little thermal stress, and window goes away.

Windshields use laminated glass -- a layer of plastic between two sheets of glass, so that if the glass fails, it's held in place.
posted by eriko at 7:45 PM on January 29, 2009 [1 favorite]

I agree on spontaneous glass breakage. The most spectacular I've seen was on a cold day in New England -- a huge, plate glass, ground level cafeteria window. Someone -- a kid, mind you, this was in school, and not a big kid at all -- leaned on it, as we were wont to do, and it just almost kind of dissolved.
posted by Weighted Companion Cube at 7:49 PM on January 29, 2009 [1 favorite]

Where are you? Some states (well, one state at least, my experience with broken windows is limited to KY) require your insurance to cover glass repairs with no charge to you, regardless of your deductible or what caused the damage. Probably worth giving your insurance a call to check.
posted by little e at 7:53 PM on January 29, 2009

I think your guess that it was some kinda pressure/heat thing may be right but I suspect that your window already had a minor crack or defect and when you shut your door after getting home, the built up pressure (and jolt from the closing/slamming of the door) in the car caused it to shatter.

I say that because something similar happened to my back windshield a while back. Yes, there was a storm and it's possible a tree branch/limb fell on the windshield and rolled off (I suspect it caused a minor crack or something) but I'm not sure. But, when I ran to get into the car in the pouring rain and closed/slammed the door after me, a few seconds later...BOOM!...the entire back windshield shattered. It didn't take 20 minutes between the shutting of the door and the shatter, but it was also summer so maybe that could account for the difference in time.

Bottom line though, in my State, there's some kind of law where car windshield replacement doesn't require you to have met your deductible so mine was replaced at no charge the next day (they came to my place of work and replaced it on the spot) and I didn't have to "prove" that the storm or whatever caused it. So, definitely check with your insurance company. You may be completely covered at no cost to you. Good luck!
posted by ourroute at 7:56 PM on January 29, 2009

Check with your insurance carrier. I know that when I had MA coverage, I also had free glass repair (as little e and ourroute mention). I didn't even know about it until some idiot broke into my truck here in Georgia while it was still plated to Massachusetts, and the lovely insurance lady said the repair was free.
posted by catlet at 8:58 PM on January 29, 2009

It happened to our Datsun when I was a kid. We had various reasons to assume it was vandalism until we saw that glass had exploded towards the outside. Whenever any glass object is made, it's annealed (slowly cooled) in an oven to reduce internal stresses that would cause it the be very brittle or even explode spontaneously. Car window glass is laminated from different formulations and tries to walk a thin line by between flexiblity and having enough internal stress to cause it to shatter on impact.
posted by bonobothegreat at 9:16 PM on January 29, 2009

The tempered glass thing is my guess too. I've had a drinking glass shatter into hundreds of tiny little pieces when it was just sitting on a table with no one anywhere near it.
posted by MsMolly at 9:23 PM on January 29, 2009

I've had it happen -- in my case, it was a door glass that wasn't aligned quite right (it had been replaced a year before due to vandalism), and a combination of the stress from that and just the right temperature, and it went "boom" -- in a store parking lot, while I was about 20 feet away (heading back to my car).

I'd agree with checking with your insurance company; mine have always offered glass breakage coverage (for $50 / $100 copay) regardless of how high my deductible was set.
posted by nonliteral at 10:07 PM on January 29, 2009

Here is an FFP about the strange nature of glass. Perhaps your window situation is similar.
posted by Tube at 11:15 PM on January 29, 2009

Not quite a car window, but my friend and I were in Target a while back and she was showing me a bottle of nail polish she picked out. She had it open in the palm of her hand. All of the sudden, "SNAP!" and we just stared as polish and glass bits were dripping through her fingers and onto the carpet. So small and stupid, but one of the freakiest things I've ever seen.

My point is, I totally believe you and whatever weird half-baked explanation that could explain this.
posted by iamkimiam at 11:44 PM on January 29, 2009

That happened to me once! It was in my parents' new Toyota Yaris, only it happened while I was driving! It was kind of scary, but even more baffling. No one believed that it happened spontaneously, but it really did.
posted by miriam at 3:05 AM on January 30, 2009

Tempered glass is designed to shatter instead of just breaking. I'll tell you a story. We were unloading a donated shower door one day and apparently bumped just a corner of it as we were unloading it. We set it down against a wall in receiving and walked away. About 10 minutes later there was a funny pop sound and a tinkling sound, and we walked in to find a pile of dust that was still breaking. It continued to break for about 25 minutes. Weird.

But it's possible that you had a teeny tiny crack/pop/car drove down the street and hit it with a pebble, whatever. Car windows are designed to break outwards when possible, look at the shape. So either at the point of impact OR hours after the fact, surface tension took over and POP goes the weasel.
posted by TomMelee at 5:12 AM on January 30, 2009

This is like that question about people who hear screaming when they fall asleep. I had no idea this was something to worry about. And yet - fascinating.
posted by CunningLinguist at 8:11 AM on January 30, 2009 [1 favorite]

This happened to me in college: It was September-ish and my car was parked in the student lot overnight. I always left my windows cracked open about an inch at top since the car didn't have a/c & I didn't like climbing into a hot car. The next morning I went outside to find my driver's side window had exploded outwardly; all the glass was on the concrete outside of the door. I was dumbfounded. It was warm out, but not super hot, and the window was open a crack so there couldn't have been some kind of pressure buildup in the car. The doors were locked, so it couldn't have been someone climbing in to kick out the window. It just blew out, all by itself. From what I remember, I think I did get a new window covered by insurance as an act of vandalism. I still have no idea what happened.
posted by cuddles.mcsnuggy at 8:18 AM on January 30, 2009

This happened to the tempered glass in our entertainment center last summer. We were upstairs, heard something that sounded like someone violently crinkling a bunch of plastic shopping bags, came downstairs and all the glass was in a pile in front of the cabinet.

I asked an engineer at work the next day and he said it could have been a couple things - he said the glass could have had a flaw in it and eventually that weakness gave. He also said there could have been tension where the glass had clips securing it to the cabinet and that could have just gave out too.

Cabinet looks lots better without the glass, but obviously you need a new window. Check your insurance, I have full glass coverage, you may too.
posted by jerseygirl at 8:25 AM on January 30, 2009

I was walking past a car a couple of years ago when this happened. My hypothesis at the time was a tiny crack in the window, combined with stress caused by heat or cold, but I dunno.
posted by EarBucket at 9:40 AM on January 30, 2009

Response by poster: Thanks, guys. I had no idea that this was so common.

According to my insurance company, there's no special glass repair coverage, so unless this eclipses my deductible (please, god, no,) I'm on the hook for the whole thing.

I called Saturn, and the guy at service said that this was the fourth exploding window he'd seen this month--but that it wasn't their fault and they couldn't do anything for me.

So now I'm calling around and getting estimates, and hopefully getting my tax return soon so that I can pay for this.
posted by meghanmiller at 10:03 AM on January 30, 2009

Agree with the above: definitely sounds like a tempered glass defect. They can take years to show themselves. It happened to my desk a couple months ago.
posted by DrJohnEvans at 10:27 AM on January 30, 2009

I had a passenger window detonate like that when I was driving it. Really freaky; at first I thought somebody was shooting at me.
posted by craven_morhead at 2:20 PM on January 30, 2009

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