I drove my Ford Taurus station wagon about miles parked...

Dear Car Talk

Dear Car Talk | Mar 01, 1994

Dear Tom and Ray:

I drove my 1988 Ford Taurus station wagon about 25 miles, parked it, and then came back two hours later and the rear window was gone. Most of the glass was on the inside. The frame was very clean, and there was no evidence of foul play. It was one of those very cold days we had this winter, and the wind was strong. Do you know what could have happened?

TOM: I think your rear window had a nervous breakdown, Betty. Glass breaks when there's too much stress on it. And stress can come from a variety of sources.

RAY: Right. For us, it could be a bad day at the office, or the dog leaving a "deposit" on the oriental rug.

TOM: But for glass, stress is caused by physical forces. Either the forces of a window frame that doesn't fit correctly, pressure on the glass by an airborne brick, or the wind, for instance. Or by extreme temperatures.

RAY: Auto glass is designed to take a certain amount of stress without breaking. So it can usually handle pebbles flying up and hitting the windshield, or below-zero temperatures.

TOM: But if the glass has an imperfection, or a small manufacturing defect, it becomes more susceptible to breaking under stress. And that's what probably happened to your window.

RAY: It's kind of like my brother. He looks normal. But all it takes is a little extra stress, and he cracks.

TOM: That comes from working with you all day.

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