I'd have to say that not 2 days go by at work when someone isn't building new brake lines for a vehicle. Those Chevy and GMC pickups from about 2001-2008 are the worst. The OEM line is not very good and the way the lines run doesn't help either. We used to make every line from scratch (if one is bad on these trucks, they all are) and it took at least a full day. Now, we keep one pre-bent kit in stock for each wheelbase, from In-Line Tube.
You're right, most people never see under their vehicles so it's up to us (auto tech's) to let them know about the rust. We've had a number of vehicles that ended up being scrapped after letting the owners know about the serious underbody rust to where it was simply not safe to drive anymore. Not just brake lines but sub frames, suspension mount and suspension pieces, etc. Yes, even suspension parts rot out (control arms and rear axle links specifically). Even had a Hyundai Santa Fe come in on the flatbed with the left rear suspension arm/bearing upright assy rotted so bad the wheel was about 5" toed out. Taurus' are bad for the front suspension/drivetrain cradle rotting away even though from the outside, the car looks pretty good yet. I can count at least 4 cradles we've replaced this year already. It's not that bad a job and the scrapyards are full of good ones (i.e. dime a dozen). One guy even scrapped a 2006 Toyota Tundra when the frame rotted so bad the truck almost bent in half. Then there's the 2010 F-150 (yes, 2010). One of the guys went to raise it on the hoist and heard a big crunching sound. Stopped and looked, the frame was collapsing at the left front hoist pad. This was on a well cared for truck that was clean and maintained. Needless to say, the owner made a call to Ford. Salt ruins cars, ruins bridges and roads before their time yet they keep using more and more. That brine stuff that they spray is worse yet. Salt if there's ice? OK, I can see that but there's no reason to spread salt on snow. None at all. Sorry, rant over now!
