Spontaneous Windshield Cracking?

"TJ" <tj.DeleteThis@invalid.net> wrote in message
news:tj-222F2E.16151710072005@news.east.cox.net...

I have seen them crack for no obvious reason.
Clearly there is a scientific reason, but it need not be so obvious as a
hammer, stone peck, etc.

My Reatta split from the top seal about 1 inch. I 'repaired' it to keep it
from running but there
was no mechanical damage which initiated it. ( A new replacement, when they
are available, is
about $1800)

My SAAB blew out a rear glass sitting in a parking place. No rock, no
damage, no nothing.

When you stress a piece of glass, and if it is not perfectly bedded, it can
crack. And it may be
nobody's fault...

(Now, shitteaux husbands, and wives, have been known to promote events which
stress may
have favored in the first place.)

If you cant prove it, it didnt happen.
 >> Stay informed about: Spontaneous Windshield Cracking? 

Someone reported the spontaneous shattering of a rear windshield
on that silly "Car talk" show on NPR today. It was very hot,
and the guys said that because glass expands, if there is
a flaw in the glass, it will break. Seems weak to me, glass
will expand much less than the metal of the vehicle, so I
dont see where the stress on the glass came from.
 >> Stay informed about: Spontaneous Windshield Cracking? 

actually on checking service bulletins on my 94 pathfinder, it seems
windshields in fact can crack for no reason, it didnt say why or how


"Professor" <briangriffey RemoveThis @sbcglobal.net> wrote in message
news:1121028933.643823.80720@g49g2000cwa.googlegroups.com...
> Windshields just don't crack for no reason... it was either hit with
> something... or had some sort or torsional stress.
>
> Professor
> Check out FlashAlert at www.telstar-electronics.com
>
> TJ wrote:
> > A friend of mine said the windshield of her 2001 Pathfinder cracked
> > overnight, just sitting inside her closed garage. The car has never
> > been in an accident or anything. It wasn't excessively hot inside the
> > garage or anything. It's like a single line crack emanating from the top
> > of the windshield down about a foot or so.I'm thinking, something must
> > have happened, windshields don't just crack like that for no reason.
> >
> > She said, "yes they do, it happened to my celica before, in the same
> > place."
> >
> > I told her I've never heard of windshields spontaneously cracking before
> > like that, that I thought it was really strange.
> >
> > *Then* she goes on arguing (sort of) with me about it, telling me it has
> > happened to *4* of the vehicles owned by her and her husband, always in
> > the same spot. She thinks it's something that just happens to cars
> > sometimes.
> >
> > This is a husband she is in the process of divorcing for some fairly
> > serious domestic violence reasons, but she still currently lives with
> > him (he's on probation).
> >
> > Now, I'm thinking, ok this guy has anger problems, and it occurs to me
> > maybe he's prone to taking it out on some windshields.
> >
> > So my question is, is it common for windshields to crack seemingly
> > spontaneously like this? I've never really heard of such a thing. I
> > mean, I'm sure it happens from time to time that the reason isn't
> > readily apparent, but to 4 out of about 6 cars these two have owned?
> >
> > Ok any thoughts appreciated!
> >
> > TJ
>
 >> Stay informed about: Spontaneous Windshield Cracking? 

"223rem" <223rem RemoveThis @sbcglobal.com> wrote in message
news:KhhAe.156$Ih7.5@newssvr33.news.prodigy.com...
> Someone reported the spontaneous shattering of a rear windshield
> on that silly "Car talk" show on NPR today. It was very hot,
> and the guys said that because glass expands, if there is
> a flaw in the glass, it will break. Seems weak to me, glass
> will expand much less than the metal of the vehicle, so I
> dont see where the stress on the glass came from.

I can assure you from personal experience that it DOES happen.
I suspect that the fit into the window port and the gasket, with
contraction and expansion due to temperature, may place
undue stresses on the glass.

Now, I had an 84 Fiero that gave me tons of problems with the front
OEM windshield fit and seal. Finally, after numerous attempts to fix it,
I asked the dealership if the glass itself could be faulty..

Guess what! It was. They replaced it under warranty and it never
gave another problem.
 >> Stay informed about: Spontaneous Windshield Cracking? 

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 >> Stay informed about: Spontaneous Windshield Cracking? 

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 >> Stay informed about: Spontaneous Windshield Cracking? 

gary wrote:


>
> In some cases heat/cooling can trigger a crack also.
>


One cold morning I pulled a car into the heated shop and the rear glass
EXPLODED so yes they can crack from this.

--

Steve

http://www.atlantaracing.com
 >> Stay informed about: Spontaneous Windshield Cracking? 

In article <pthAe.64$c41.55@newssvr30.news.prodigy.com>,
<HLS.RemoveThis@nospam.nix> wrote:

> "223rem" <223rem.RemoveThis@sbcglobal.com> wrote in message
> news:KhhAe.156$Ih7.5@newssvr33.news.prodigy.com...
> > Someone reported the spontaneous shattering of a rear windshield
> > on that silly "Car talk" show on NPR today. It was very hot,
> > and the guys said that because glass expands, if there is
> > a flaw in the glass, it will break. Seems weak to me, glass
> > will expand much less than the metal of the vehicle, so I
> > dont see where the stress on the glass came from.
>
> I can assure you from personal experience that it DOES happen.
> I suspect that the fit into the window port and the gasket, with
> contraction and expansion due to temperature, may place
> undue stresses on the glass.
>
> Now, I had an 84 Fiero that gave me tons of problems with the front
> OEM windshield fit and seal. Finally, after numerous attempts to fix it,
> I asked the dealership if the glass itself could be faulty..
>
> Guess what! It was. They replaced it under warranty and it never
> gave another problem.

Windshields on occasion do bust on their own, always have. It's rare
though, and not a big problem by any means.

Big fast temperature changes are hard on glass, like summer in the hot
sun, and splashing it with cold water. Even thats not such a big
problem... but if you have a windshield with a flaw, damage, or one that
wasn't tempered correctly and still has some internal stresses, that
would be a prime time for it to go.

Even after saying all that, by far the biggest killer is mechanical
shock... as in road debris, accidents, vandalism...

Erik

PS, a little off topic, but years ago I picked up the front end of a
late 60 something Caddy with a floor jack, and the windshield busted
just as the front wheels left the ground... wow, you should have heard
the foul language that generated.

E
 >> Stay informed about: Spontaneous Windshield Cracking? 

On 7/10/05 9:16 PM, in article erik-0159DA.18163410072005 RemoveThis @news.verizon.net,
"Erik" <erik RemoveThis @dejathis.com> wrote:
> Big fast temperature changes are hard on glass, like summer in the hot
> sun, and splashing it with cold water. Even thats not such a big
> problem... but if you have a windshield with a flaw, damage, or one that
> wasn't tempered correctly and still has some internal stresses, that
> would be a prime time for it to go.
I've done that twice (once at 8am, never thinking it would have been hot
enough) and both times the windshield cracked. Now I feel them and if they
are not cool to the touch I don't wash the car.
 >> Stay informed about: Spontaneous Windshield Cracking? 

TJ wrote:

> A friend of mine said the windshield of her 2001 Pathfinder cracked
> overnight, just sitting inside her closed garage. The car has never
> been in an accident or anything. It wasn't excessively hot inside
> the garage or anything. It's like a single line crack emanating from
> the top of the windshield down about a foot or so.I'm thinking,
> something must have happened, windshields don't just crack like that
> for no reason.



Don't know where she lives, but rust in the pinchweld can cause
localised pressure that can lead to a crack.

Has the windshield ever been replaced? If so, failure to patch the
nicks in the paint will cause rapid rusting if the vehicle is in a
Northeastern area of North America.
 >> Stay informed about: Spontaneous Windshield Cracking? 

John S. wrote:

> The glass would have to have been weakened at some point. A small
> stone or something else thrown up by the vehicle in front is the most
> likely cause. A tiny chip can spread into a window spanning crack in
> no time.


Chips in the edge of the glass will have the same effect. You can't see
them because they're under the trim.

Thermal flexing and vibration will eventually turn the chip into a
crack.
 >> Stay informed about: Spontaneous Windshield Cracking? 

I'm just wondering, if there's anything weird about the garage (besides
her husband). Is there a big temperature differential between the
ceiling and floor (does the ceiling get real hot in summer or cold in
winter).

I used to drive my car a lot and went through about one windshield a
year (due to rock chips causing cracks). I now get replacement windows
with Edgeguard (has a plastic strip running along all the edges that is
supposed to keep the edges from starting cracks from rocks, etc). It
works (IMHO).

Jim
 >> Stay informed about: Spontaneous Windshield Cracking? 

After working in a glass shop for several years, I've seen some wierd things
that can shatter glass, or even cause laminated to crack and then run. The
3 basic types of glass are laminated(used in windshields), tempered(used in
the other windows) and plate. Tempered is very damage resistant, however
when it does break it just explodes into thousands of tiny pieces. Tempered
has to be manufactured at the size needed, it can not be cut after the fact,
unlike both plate and laminated. Plate glass when it breaks leaves larger
jagged pieces(many older homes windows are plate). Laminated is just 2
pieces of 1/8" plate glass with an adhesive sandwiched between them. During
installation, there are rubber shims placed at the edges of the windshield
for proper alignment and to keep it from shifting. Between the glass and
the lip of the body a rubber based sealant is used to both weatherproof and
provide sufficient expansion. Its unusual for factory windshields to leak
or crack from the edges, but they can if there is a thin spot in the sealant
allowing the glass to impact the lip. However, this would most likely
manifest itself within a few days of manufacture, not several years down the
line.

Glass is fairly stable thermally as long as the changes are gradual, however
rapid changes can crack it(or worse in the case of tempered). Driving out
of a heated garage into sub zero weather can cause a rapid enough rate of
thermal contraction to crack it. Even running the defrost at the hottest
setting when its below zero can be bad, it causes the inner layer to expand
while the outer layer stays contracted. When this happens, typically the
inner sheet will buckle and crack.

The other windows on the car are a different matter. The rear glass is
usually tempered(as are the side windows), especially if it has an electric
defrost. Laminated won't work here as the heat produced will melt the
adhesive. Tempered glass usually breaks from the edges inward. The 2
biggest reasons for tempered glass to fail are overpressure caused by high
powered stereo systems, and objects striking at a high rate of speed, both
of which are fairly common problems.

I've had 8 vehicles since I started driving, ranging from a 68 Mustang to a
93 Ram diesel. I've logged better than 1.5 million miles total, did 740k on
the ram before it got totaled in sept 96. Out of that I've changed 2
windshields(the mustang and the ram), a couple of side windows, and one rear
window(an 89 Escort I put in a spin on gravel and hit rear first on an
embankment, the rear window came out in one piece and shattered when it hit
the mud). The ram has been to almost every state in the lower 48(never hit
Maine, Vermont or New Hampshire), and covered a good chunk of Canada also.

In your friends case, the most likely cause was her husband hitting the roof
of the vehicles near the lip of the windshield. I bet there are slight
dents in the roof, though it could have happened from the inside. The
chances of 4 out of 6 cracking in the same spot are astronomical, or she has
gremlins in her garage. I bet that after he leaves, she won't crack anymore
windshields, except for rocks.

"TJ" <tj DeleteThis @invalid.net> wrote in message
news:tj-222F2E.16151710072005@news.east.cox.net...
>A friend of mine said the windshield of her 2001 Pathfinder cracked
> overnight, just sitting inside her closed garage. The car has never
> been in an accident or anything. It wasn't excessively hot inside the
> garage or anything. It's like a single line crack emanating from the top
> of the windshield down about a foot or so.I'm thinking, something must
> have happened, windshields don't just crack like that for no reason.
>
> She said, "yes they do, it happened to my celica before, in the same
> place."
>
> I told her I've never heard of windshields spontaneously cracking before
> like that, that I thought it was really strange.
>
> *Then* she goes on arguing (sort of) with me about it, telling me it has
> happened to *4* of the vehicles owned by her and her husband, always in
> the same spot. She thinks it's something that just happens to cars
> sometimes.
>
> This is a husband she is in the process of divorcing for some fairly
> serious domestic violence reasons, but she still currently lives with
> him (he's on probation).
>
> Now, I'm thinking, ok this guy has anger problems, and it occurs to me
> maybe he's prone to taking it out on some windshields.
>
> So my question is, is it common for windshields to crack seemingly
> spontaneously like this? I've never really heard of such a thing. I
> mean, I'm sure it happens from time to time that the reason isn't
> readily apparent, but to 4 out of about 6 cars these two have owned?
>
> Ok any thoughts appreciated!
>
> TJ
 >> Stay informed about: Spontaneous Windshield Cracking?