A lot of GMC Sierra owners put these trucks through tough conditions. So strengthening your Sierra's brakes by replacing the brake lines will improve braking performance. Make sure you know which sections of brake line you are replacing; the sections closest to the calipers are the easiest for a non-expert to work on.
Raise the truck on jack stands that safely support a GMC Sierra. Remove the wheels to reach the brake lines you are replacing.
Locate the brake master cylinder. This is in the rear of the Sierra's engine compartment, near the driver's seat (since it must connect to the brake pedal).
Trace the brake lines as they run from the master cylinder to each wheel. Look over each line to see what sections it may be divided into. Take note where and how the lines are bent and bend the replacement lines the same way.
Remove the brake line by disconnecting the connector bolts. Use two line wrenches as there should be two bolts at each connector. Remove the line at the caliper brake hose first to avoid damaging the hose.
Install the replacement brake line, starting at the end closest to the master cylinder. The new line should be measured and bent to match the original line.
Bleed the brake system. Connect the opened bleeder valve on the caliper to a container of brake fluid with a vinyl tube. Have another person press on the brake pedal to remove the air. Top off the master cylinder afterward.
Attach the wheels and move to the other end of the truck. Test the brakes once the entire brake line has been installed.
