Brake issue could have been avoided

Dear Mike: I was working on the suspension on my old Mustang, and had to remove a brake line to get it out of the way. In doing so I twisted up the end of the hard line like a pretzel. So I cut it off and used a compression fitting to patch the end of the line. Now it leaks, and the pedal is always spongy.

— T.O’G., Lansing, Mich.

A: Working on old cars is always an exercise in caution and craftiness, no?

Those steel brake lines have very poor anticorrosion coating, if any at all. They are generally not even galvanized, only painted. After a number of years of being bathed in road dirt and salty spray, they can become nearly impossible to remove.

What happened to you is a common failure mode. The hollow steel line corroded and fused to the steel fitting at a place where it’s supposed to rotate freely, allowing the fitting to thread into its mating fitting, caliper or master cylinder. When you applied enough torque to unscrew it from the fitting, the line corkscrewed up like a wrought-iron porch baluster.

Your second mistake: Never, ever use a compression fitting on any brake line. The pressure in the brake line during a panic stop is about two orders of magnitude too high for the design of a compression fitting.

You could acquire or rent a flaring tool, re-create the factory single or double flare and then splice in a longer piece of line, but don’t try this. Aside from the fact that it’s difficult to get a good flare without some practice, think about the line you’re trying to save — one you already know to be weak and heavily corroded.

The only remedy I can recommend is that you replace the entire steel line. That’s not that big a hardship, as the line itself can be had for only a few bucks down at the auto-parts store. Measure the line carefully, and get one that’s as long or even a few inches longer. There are a couple of different styles and sizes of fittings, so be sure to match them up. Simply swap in the new line and bleed the system.

On an older car with known corrosion/brake-line issues, I’d probably replace every line, not merely the busted one. Take a critical look at the rubber lines as well, as they don’t last forever.

A wider issue: To prevent this from happening in the first place, use penetrating oil on these fittings a day or two before you’ll need to unscrew them. Whack them smartly with a hammer a few times to loosen them. You also can heat them with a torch, then spray them with cold water a few times. The thermal stress will break up the corrosion. Continue to spray them with penetrant as well.

Here’s one last tip: Always use a flare-nut wrench to turn these types of fittings, to avoid rounding them off. Save the crescent wrench for working on the kids’ swing set or the sink.

Dear Mike: My father-in-law says that he shifts his automatic transmission into neutral at traffic lights to save wear and tear on the trans and to save gas. Right or wrong?

My son-in-law says that he shifts his manual transmission into neutral at stoplights to save wear and tear on the clutch. Right or wrong?

— M., via e-mail

A: I’m afraid to ask what your wife does at stoplights.

I prefer to leave automatic transmissions in drive at traffic lights. The transmission has an internal oil pump that spins constantly, providing lubrication and cooling regardless of what gear the car is in. There are no slipping friction surfaces, only the fluid-coupled torque converter urging the car to creep forward.

Shifting to neutral means cycling the band clutches in and out of gear, while causing several valves to open and close. In addition there are far more moving parts inside the transmission when idling in neutral than when idling in drive. Moving the shifter into neutral and back into drive can wear out the linkage.

I would recommend shifting into neutral if you’re lighting a cigarette, changing a CD or programming the nav system, however, so that you don’t inadvertently creep into traffic. Safety first.

Manual transmissions, on the other hand, are a different kettle of gears. In gear and with the clutch depressed, there are no moving parts at all aft of the clutch disc. But the throwout bearing is loaded and spinning, wearing out.