There are three ways to approach a brake line replacement job: buy a direct replacement brake line, use a pre-flared brake line, or invest in a brake line kit and make the whole thing yourself. With the first two, reusing the old fittings isn’t an option: the line comes with new ones. Use a brake line kit to make your own from scratch though, and now you have the option to reuse those old fittings. Here are some points to consider.

Reasons for Replacing Brake Lines

Routed along the underside of your vehicle, brake lines are exposed to salt, dirt, and whatever deicing chemicals are used in your part of the world. Unless your ride is blessed with stainless steel, the lines are going to corrode. Nickel copper and poly-vinyl fluoride (PVF) lines will last longer than steel, but their life is still finite.

Brake lines can also corrode from the inside out. This happens if you don’t change the brake fluid at the prescribed intervals, especially if it’s hygroscopic (water-absorbing).

Other reasons for replacing brake lines are because they got damaged somehow, because you’re modifying the vehicle, or because the end fittings or flares have been damaged.

Brake Fittings

Rigid brake lines are flared out at the ends. A flare nut mounted on the line screws into a mounting block, trapping and compressing the flare in the process. This is what seals against brake line pressures as high as 2,000 psi.

Flexible brake lines, or hoses, are often connected with banjo fittings. These are two-piece fittings where a hollow bolt passes through the center of a ring-shaped union fitted to the end of the hose. Copper crush washers sit against each face of the ring to create a seal.

Reuse or Replace the Fittings?

If you’re working with a brake line kit you have the option of reusing fittings from the lines you’ve just removed. As a general rule, don’t. Here’s why.

  • Fittings taken off a vehicle could have cracks or corrosion not visible to the eye
  • Threads may be damaged
  • Hexagonal faces could have been rounded

Distorted or misshaped threads will raise the torque needed for fastening, letting you think they are tight when they’re not. If hex sides are rounded or damaged from being clamped in grips, a flare nut wrench could slip and do more damage. If you get the fitting done up tight it may never come undone again!

With a banjo fitting, while you can reuse the union it’s best to replace both the crush washers and the bolt. The washers act as gaskets and once used they’ve deformed and may not work as well next time. Plus, the bolt stretches when tightened, and if it’s been over-torqued previously there’s a risk of it snapping.

The Bottom Line

If you’re going to the effort of replacing a brake line, don’t cheap out on fittings. It could lead to premature failure, and who wants to risk that in the braking system?