As you step on the pedal, the different parts of the brake system will all spring into action. The fluid from the master cylinder is transported to the calipers. The brake pads then clamp on the rotors to slow down the vehicle or bring it to a halt. The fluid passes through the brake line to get to its final destination.
Air in the brake lines has to be bled out, as this can lead to a soft brake pedal or a pedal that sinks too low. In case the brake lines have totally gone bad, consider replacing them right away. This will save you from impending brake trouble.
Bleeding air out of the brake lines
Bleeding the air must be done whenever the brake line is disconnected, as well as when the master cylinder runs low of brake fluid.
Step 1: Use a vehicle manual when looking for the bleeder valve in your vehicle.
Step 2: Begin at the rear wheels when bleeding out air in the brake lines before working on the front wheels.
Step 3: Check if the bleeder valve nut is stuck or frozen as you loosen the nut with a correctly sized wrench. Make sure that you retighten it immediately before the fluid ever gets to escape. A frozen nut can be fixed by applying some anti-rust penetrating oil.
Step 4: Take off the master cylinder's cover. The cylinder should be filled with brake fluid.
Step 5: Use a rubber hose and clean container or bottle. Pump the brakes so that fluid will run from the bleeder valve through the hose and, finally, into the container. To let air and fluid escape, adjust the bleeder valve a bit. Tighten back the bleeder valve once there's no longer air coming out of the valve, only fluid.
Step 6: Refill the master cylinder with new fluid or use the one you collected in the container. Make sure that the cylinder doesn't dry up or lose too much fluid as you bleed out air in the brake lines.
Step 7: Clean up the bleeder nut, wiping off any fluid streak. To make sure that everything's back in place, go on a test drive and then check for leaks.
Replacing the brake lines
Step 1: Remove the old brake line, which is most probably connected to metal parts. Use two wrenches to pull apart the fittings. The wrench should go on each fitting as you loosen the connection. Brake fluid may leak out any time. In this case, you need to have a cloth or rag to wipe this off.
Step 2: Install the new brake line. Hand-thread the connection till it's tight enough. Once you're sure that the fittings go together well, use the two wrenches to make sure that the connection is sealed.
Step 3: Top up the system with brake fluid after installing the brake line.
Step 4: Bleed the brakes once you've refilled the system with brake fluid.
Step 5: Check the brakes as you take the vehicle for a spin.