How to install and replace brake, fuel and hydraulic lines
Cutting to Length
To determine the length of the brake line needed, use stiff wire, solder, a tape measure or the old brake line as a guide. Cut to the required length using a tubing cutter. Do not distort the brake line by over-tightening it in the cutter. File the ends to ensure it's square and remove burrs from the inside and outside edges. Blow filings out of the brake lines.
Selecting the Brake Line Nuts
If you aren't reusing the original nut, be sure the new nut matches with diameter, thread pitch, length, non-threaded lead, etc. Long style nuts are preferred for high vibration applications. Install nut on brake line before flaring.
Flaring Brake Lines
The appropriate single, bubble or double flare can be formed, using a good quality flaring tool such as the 007 brake line flaring tool. Tools with serrated grips are bad engineering practice for flaring any tubing. If you have been able to flare steel brake line with your tool, you will be able to flare our tubing with it. If you haven't been able to flare any tubing with your tool, it is probably the tool, and not you. Ensure that the dies grip the tube securely without deforming the tube section or denting its surface. Check that the flare is of the correct profile for the unit and component involved. Also make sure that the flare has been formed centered on the tube.
Installing the Brake Lines
Bend the nutted and flared tube carefully to shape, so that it will fit easily into position. Bends should be smooth and have as large a radius as possible. For tight bends on the larger sizes, a rolling die bending tool should be used. A minimum bend radius of three times the tube diameter is recommended. Tubing should not be kinked or strained into position. The nut should spin freely on the tubing. Lubricate the threads and outside of the flare with anti-seize compound. When tightening the nut, make sure the tubing doesn't twist while doing so. Do not over-tighten the nut.
As a general rule from finger tight, continue tightening the nut until you feel it draw down tight, then tighten approximately 1/6" turn more. Do not over-tighten.
All brake lines should be supported at regular intervals along their length, using steel or plastic clips, each attached firmly to the body or chassis of the vehicle. When brake lines follow axle casings or suspension arms, which can induce vibration of the tube, it is essential to secure tightly. Tie wraps work well to secure to rear axle housings. Clips should be spaced at intervals of approximately 12 to 13 inches but no farther apart than those used for steel brake lines.