Rusted brake lines in GM pickups demonstrate the twilight zone of auto safety

This week's hearings into the botched recall of 2.6 million cars by General Motors produced more heat for the automaker and regulators than light, with GM chief executive Mary Barra excorciated by lawmakers for the automaker's mistakes. All of the questions built from the same unstated premise: cars and their parts should always be safe, and automakers like GM should fix them when they’re not.

Yet in many cases, how the industry and government regulators define a safety defect isn’t a yes-or-no question — and it’s another GM issue involving millions of vehicles that demonstrates the twilight zone in between.

For more a decade, thousands of owners of GM full-size pickups and SUVs — mainly the Chevy Silverado and GMC Sierra — have complained to federal regulators and GM about rusted brake lines. The trucks use small steel pipes to route brake fluid between the wheels and control pumps, and those lines can rust to failure, especially in northern states that salt their roads frequently in winter.

It’s a well-known problem among GM truck owners and mechanics, several of whom have documented their troubles in online videos. While most of the complaints involve models made between 1999 and 2006, some newer vehicles have seen complaints as well.

And scores of owners have reported a sudden brake failure while driving due to their rusted brake lines giving way on the road. One owner told federal officials about just such a failure in a 2005 Silverado this February: