The safety of your vehicle, and more importantly of your life largely depends on the efficiency of brake lines. If you feel that the brakes have to be applied harder or the brakes are not functioning properly, then there can be rust in the brake lines. When the brake lines get dirty or rusted, the brake fluid cannot flow efficiently from the master cylinder to the wheels and cause failure of the brakes.
Step 1 – Inspect the Rust
First, lift the car using a jack or park it on a car lift. Identify the brake line and inspect it. The brake line can be either partly or completely rusted. If the line is partly rusted, then the brake line has to be cleaned and brought into a perfect working condition. If they do not work properly even after cleaning, then it has to be partially or completely replaced.
Step 2 – Remove The Brake Line
Remove the brake line by unscrewing the brackets using wrenches or by removing the clips holding the brake line to the frame. Measure the required amount of the brake line along with the bending using a measuring tape. If it is partially rusted, it has to be cut with a tube cutter.
Step 3 – Prepare the Brake Line
Buy a new brake line according to the required measurements and the size. Keep the old brake line and new brake line besides each other. The new brake line has to be bent to match that of the old one. Use the tube bender to bend the brake line.
Step 4 – Fix the Brake Line
Fix the prepared new brake line in the car. The compression kit has two end caps, a center tube and two ferrules. Fix the ferrule at one end and the end cap at the other end. Now fix this brake line with the center tube by hardly pressing it into the center tube. Fix them with the help of the end cap. Fix one part of old brake line to new one and the other end to the barrel. If there are clips to place the brake lines in position, the brake line has to be clipped to the manufacturers’ clips.
Step 5 – Bleed the Brake Line
Next, the air from the brake line has to be removed by bleeding the brake line. Fill the master cylinder completely with the brake fluid. Ask someone to start the car and press the brake pedal. The bleeder screw on one of the wheels must be loosened to let the air go out completely until the brake fluid starts flowing. Repeat this for all other wheels and refill the master cylinder completely with brake fluid.
source- http://www.doityourself.com/stry/how-to-clean-rusted-brake-lines