Sudden windshield crack.

In the absence of an impact, the leading candidates are torsional stress in the body structure or thermal stress in the glass. For example, have you (or a shop) recently jacked up one corner or washed the vehicle when it was hot? If the crack is parallel to an edge, I'd suspect thermal.

Hmm. No. However, I did put on the defogger/defroster..outside temperature at about the freezing mar. I noticed a TINY chip, right in the middle of the crack line.

I had someone throw a rock at me in a construction zone (No surprise there) , and I got a chip. Went in to work and parked. By the time the workday was done I had an 11 inch crack. . . . But it was a cold day, too.

Charles of Schaumburg

I think you've found your cause.

Probably liberals in there, to a man. :-)

Pesky liberals. For sure. ;-)

That chip is what caused the crack. In the future, if you get a chip in the windshield, take it to one of those places that use epoxy to fill in the chips to prevent a crack from forming.

Bingo!

Is your type of vehicle a secret??? "sharx35" wrote in message news:cmY_g.35758$P7.14531@edtnps89... A long crack, about 2 inches up from the bottom of my front windshield, appeared this evening. There was no recent contact with any flying object. What gives?

No matter what you say, there was contact with an object.

That's chip is probably what started. When you were parked an object may have been thrown up by passing traffic.

Last Dec. I had a very small something hit my windshield, right in front of me. I saw no obvious damage, but the next day, after parking in my unheated garage, there was a 1 ft. horizontal crack. Looking closer I saw a very small pin hole on the crack line.

Ray, I know that. This particular chip was the next thing to invisible, it was that small.

99 Camry CE...made in Japan. 6 cyl. "Roadrunner Newsgroup" wrote in message news:0_b%g.26943$ snipped-for-privacy@tornado.rdc-kc.rr.com... Is your type of vehicle a secret??? "sharx35" wrote in message news:cmY_g.35758$P7.14531@edtnps89... A long crack, about 2 inches up from the bottom of my front windshield, appeared this evening. There was no recent contact with any flying object. What gives?

Yeah, that's pretty much what happened. Now, the crack, as long as it is, is below the "line of visibility", i.e. it only affects my view of part of the hood. That being the case, should I wait until spring, for more clement temperatures? Or, is the structural integrity of the Camry affected by this crack, therefore making it important to replace the windshield now, rather than later?

I believe there's no structural implication. Some jusirdictions require periodic official inspections of a vehicle's serviceability. A cracked windshield can trigger rejection. Now that you know the weather wasn't a factor the timing is your choice.

Nah, just all sorts of loose stuff on the road and one poor guy just happened to catch this rock just right. . . . Happens in construction zones. Most of the expressways seem to be perpetually under reconstruction. (Maybe THEY lost the Civil War?) Sometimes when they work on a roadway they don't clean up very well.

Nah, but I've never seen a crack go from nick to 11 inches in a mere 8 hours like that before.

Charles of Schaumburg

Like several quintillion air molecules.

Sorry, but there are a lot of stresses in some windshields, and if those stresses are given a focus to relieve themselves - that chip - they are going to.

Windshields are complex, starting with flat float glass. They take two pieces of flat glass and heat them up just enough to get soft and slump into molds, then anneal and temper them. Then they take the two glass sheets and bond them together in a lower-temperature oven with a sheet of special plastic to make Safety Glass. Trim the edges, put the ID "bug" mark in the corner, and they can pack and ship it.

It works fine for flat glass and rarely breaks because the two pieces started out flat and stressless, and mated easily. And most building windows don't collect stone chips.

But with windshields, if the two mating molded curved pieces aren't perfectly curved and matched to each other (and it's almost impossible to get the two molds that well matched, within a millimeter over the entire width...) the process of bonding the two sheets together will induce bending stresses in one or both panes of glass.

Glass will take a lot of abuse, so it works fine for many years - but give it a stone chip to start the crack, and those stresses will relieve themselves.

Ray: The only time the resin fills are effective is on a "Bulls-eye" conical break of the outer layer. If the bulls-eye is perfectly clean and doesn't start a stress crack as an offshoot, the resin replaces the air in the gap and makes it optically disappear.

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Not to mention stresses induced by the bonding material itself curing (often they shrink slighly) and the fact that windscreens are fairly often considered a structural part of the vehicle these days, adding significant torsional stiffness to the shell.

Warranty claims on glass require authorization by the district service manager, and whenever someone asked me to look at a cracked windshield, I'd explain my simple test to the customer before I saw the car. I would take a ball point pen and run it along the length of the crack. If the pen rolled the length of the crack without hanging up anywhere, I would authorize a new windshield, but if it hung up, it was due to a chip.