Even though the stock brake lines on your Ford Focus should last a long time, replacing them with stainless steel lines can help the car last even longer and look better. Consult with your mechanic and get a replacement kit from a reputable dealer before taking on such huge maintenance.
Raise the car on jack stands and remove the wheel corresponding to the brake line you need. This helps you reach the brake line and access the brake caliper after the installation.
Open the hood. Locate the brake master cylinder at the rear of the engine compartment. It's a metal cylinder with a plastic reservoir tank on top. Trace the brake lines that run from it and to each wheel.
Look over the whole brake line. It may be divided into sections. If you're replacing a damaged line, you may only need to replace one piece.
Note how the line is bent and coiled in multiple places. This reduces the strain on the line while you drive the car. Bend the replacement line in the same way.
Measure the length of the old pipe and compare it to the new. You need to cut it to the original pipe's length if the replacement pipe is longer. Then, flare the end so it fits the connector bolts.
Remove the brake line by disconnecting the bolts at the master cylinder and the brake hose. You need two line wrenches because there are two bolts on each connector. Start at the end closest to the brake hose and caliper.
Support any piece of the line still connected with a strong wire. This is especially true of a piece connected to the brake hose on the caliper. You don't want to stretch or damage the hose in any way.
Plug the holes in the brake line to prevent losing excess fluid, especially at the end near the master cylinder. Use rubber, an anti-absorbent cloth or any clean material that won't absorb the fluid.
Install the new brake line. Start with the end closest to the master cylinder, then to the hose. Connect the bolts to the connectors by hand and then tighten them with your line wrenches.
Clear the brake system of air. Open the bleeder valve on the caliper and attach a vinyl tube to it. Have another person press on the brake pedal to remove the air. Top off the master cylinder if necessary.
Attach the wheel and lower the car. Repeat this process for the other ends of the car as needed.
Bleeding the brakes must include special Ford-issued testing equipment if your Focus has anti-lock brakes. Consult an expert on Ford vehicles.