How to Double Flare Auto Brake Lines

Between the master cylinder and the wheels on your car are brake lines. These lines are metal for most of their length and, in the front, rubber for the last 10 to 12 inches. Brake fluid is hygroscopic, which means that it has a tendency to absorb water. This buildup of water in the brake lines causes the brake lines to rust from the inside out. When this happens, you need to replace the metal line with a new one. The most important part of replacing brake lines is making sure they seal properly. This means making double flares at the ends.

Instructions

1

Measure and cut the replacement pipe to length. File the end of the pipe to remove any burrs and to make fine adjustments to the angle of the cut. The end of the pipe needs to be as perpendicular to the run of the pipe as possible. Use the rat tail file to debur the inside of the pipe.

2

Chamfer the end of the pipe with the medium file. Place the file at a 45 degree angle to the tip of the pipe and bevel the edge of the pipe around the lip of the pipe. The chamfer needs to be smooth and consistent. Slide the threaded fitting over the end of the pipe, with the threaded end towards the end of the pipe.

3

Insert the pipe into the pipe clamp block with the end of the tubing hanging out the beveled side of the clamping block. Place the flaring die flat on the clamping block next to the pipe. Adjust the amount of exposed pipe to make contact with the underside of the flaring die. Tighten the clamping block as much as possible. Use a small wrench if needed to make sure the camp is tight.

4

Clamp the clamping block into the vise tightly. The end of the clamping block with the pipe end in it needs to be exposed.

5

Place the flaring die into the end of the pipe, with the stem of the die inside the pipe to keep the die centered.

6

Place the flaring anvil over the clamp block with the pointed end of the threaded screw resting in the end of the flaring die. Turn the bolt clockwise until the flaring die makes contact with the clamping block.

7

Turn the threaded bolt counterclockwise and remove the anvil from the clamping block and the die from the pipe end. The end of the pipe will resemble a bell.

8

Place the flaring anvil over the clamping bar, with the anvil point in the end of the pipe. Turn the threaded bolt clockwise until the end of the pipe folds in on itself. Remove the flaring anvil. Loosen the clamping block and remove the pipe from the block.