Exploding rear window ?

I am the owner of a 2006 Mazda 5. Last night in the dark, while ON A HIGHWAY, my back windshield seemed to "explode". Tiny pieces of glass went everywhere in the far back section. There was a LOUD popping sound when it happened. We did not see if anything was dropped onto the car. Could the temperature of the heater have anything to do with this? Has this happened to anyone else????? PLEASE HELP....

Mazda5girl:

It is highly unlikely that this was caused by anything other than a thrown rock or a shot from a bb gun or pellet gun.

My daughter had it happen in her saturn.

All side and rear glass is 'tempered' so that, if broken, it will completely break into tiny beads of glass like gravel. Even if the impact is at the far end of the glass, the whole window will go.

Also, this glass is odd. It can resist a substantial blunt force impact without breaking, like someone kicking a window, but a tiny nick at the edge might break it.

I once broke a rear window when using a special tool, like a screwdriver to remove the trim. I must have nicked the edge of the glass, but so lightly, I didn't even notice, and my entire window exploded. Also, I have had friends break their rear window on a minivan simply by closing the rear hatch. Another friend watched the rear window explode on her brand-new 2-day-old Grand Prix when she closed her drivers door.

So, how can glass be so strong and so weak at the same time? As described to me, it's due to internal stresses. As glass is manufactured, it is formed when extremely hot, then cooled down. If the cooling is uneven, internal stresses develop. Tempering is supposed to relieve all the stresses, but sometimes doesn't work. Therefore, if you are unlucky to stress the glass along a pre-existing area of internal stress it may break.

This is rare, but does happen.

So, yes a bullet, or pellet or rock will break a window..... I know from personal experience. But this does not mean you were shot at. Your glass could have broken due to stress and bad luck, as described above.

We also had the rear window of our 2009 Mazda 5 explode today. My wife was backing up in a parking lot when it happened. I cleaned up all of the debris and there was no sign of a rock, bb, tree limb, or other source object, so it appears to have been a stress fracture.

The car is in warranty, so I called the dealer before touching the car, but there appears to be no way that I can prove that the damage was caused by a defective window or defective installation.

My concern now is not to repeat this with a replacement window. Window replacement seems to be a great Fly-By-Night business opportunity for companies that will come out and do a quick job in the parking lot. Apparently window mounting is an important part of overall vehicle safety in terms of preventing frame crumpling, guiding proper airbag deployment and stopping ejections. I understand that it is common to place a new urethane seal over top the old, which provides for bad adhesion and increased stress on the new window because of the changed geometry. Secondly, if the old urethane seal is properly removed, apparently, the paint needs to be reprimed so rust will not develop, which will also lead to poor adhesion. There are also apparently issues regarding selection of the right urethane for a particular glass at a particular application temperature.

Should I assume that any company offering to do the job in the parking lot is not priming the metal? I would appreciate any suggestions people have.