Because of their location under the car and near the wheels, automotive brake lines are subjected to moisture, dirt and road salt that can get trapped near the fittings. If the brake lines are not cleaned occasionally, the buildup of moisture can eventually cause rust and corrosion, causing the threaded fittings on the brake lines to seize. Loosening them for a routine brake job can become quite a project unto itself.
Loosen the lug nuts on the wheels and raise the vehicle with a floor jack. Place the vehicle securely on jack stands and remove the wheels to gain access to the brake lines.
Spray degreaser on the brake lines where they are rusted and where they thread into the fittings for the caliper or into the fitting that goes to the soft line. Most brake systems have a hard line that goes to the fitting near the caliper. From there, a soft line then goes to a short hard line that is bolted to the caliper.
Let the degreaser soak in for a few minutes and then thoroughly scrub the brake lines with a wire brush. Use a rag to remove dirt, debris and oil.
Spray a generous amount of penetrating lubricant, such as PB Blaster or something similar, onto the rusted brake lines where they are threaded into the fittings. Let the lubricant soak in for several hours, periodically spraying more lubricant onto the lines. You can even let the brake lines soak overnight.
Heat up the brake line fitting with a small torch. Run the flame back and forth on the fitting for a minute or so. Warning: Be extremely careful when using any type of heat source near an automobile. Be sure that there are no fuel lines or anything flammable near the heat source.
Use a line wrench to loosen the fitting on the brake line. A line wrench is an open-ended wrench that encircles more of the brake line fitting than a normal, open-ended wrench. This gives a much more solid hold on the brake line fitting and reduces the chances of stripping the bolt. It necessary, brace the wrench with a piece of wood or something to avoid bending the brake line.
