GM Celebrity/Century/Ciera/6000 1982-1996 Repair Guide

Steel Brake Lines


See Figure 1

Loosen the steel brake line fittings using flare nut wrenches only. If the steel line starts to twist, stop and lubricate with penetrating oil. Move the wrench back and forth until the fitting turns freely. A backup wrench should be used when loosening steel-to-rubber brake hoses. Steel brake lines can be repaired by installing a double flare after the damaged portion has been removed. The tools needed for this procedure may be purchased at a local hardware or auto parts store. Steel brake lines MUST be double flared.

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Fig. Fig. 1: Loosen the brake line fittings with a flare nut wrench


See Figure 2

Flaring steel lines is a skill which needs to be practiced before it should be done on a line which is to be used on a vehicle. A special flaring kit with double flaring adapters is required. It is essential that the flare is formed evenly to prevent any leaks when the brake system is under pressure. Only steel lines, not copper lines, should be used. With the supply of parts available today, a pre-flared steel brake line should be available to fit your needs. Due to the high pressures in the brake system and the serious injuries that could occur if the flare should fail, it is strongly advised that pre-flared lines should be installed when repairing the braking system. If a line were to leak brake fluid due to a defective flare, and the leak were to go undetected, brake failure would result.

A double flaring tool must be used, as single flaring tools cannot produce a flare strong enough to hold the necessary pressure.

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Fig. Fig. 2: Brake lines must be steel with double flared ends

  1. Obtain the recommended tubing and the correct size steel fitting nuts. The outside diameter of the tubing is used to determine the size.
  3. Cut the tubing to length. The correct length is determined by the measurement of the old pipe. You can use a piece of string to measure. Add 1 / 8 in. (3mm) for each flared end.
  5. Make sure the fittings are installed before starting to flare. Chamfer the inside and outside diameter of the pipe with a deburring tool.
  7. Remove all traces of lubricant from the pipe and flaring tool. Clamp the flaring tool body in a vise carefully.
  9. Select the correct size collet, then the forming mandrel for the pipe size use, insert the proper forming mandrel into the tool body. While holding the mandrel in place with your finger, thread in the forcing screw until it makes contact, then begins to move the forming mandrel. When contact is made, turn the forcing screw back one complete turn.
  11. Slide the clamping nut over the brake pipe into the correct collet. Leave approximately 0.75 in. (19mm) of tubing extending out the collet. Insert the assembly into the tool body The brake pipe end must make contact to the face of the forming mandrel.
  13. Tighten the clamping nut into the tool body very tight or the pipe may push out. Wrench-tighten the forcing screw in until it bottoms. Do not overtighten the forcing screw or the flare may become oversized.
  15. Next back the clamping nut out of the tool body and disassemble the clamping nut and collet assembly.
  17. Bend the pipe to match the old pipe. Allow a clearance of at least 0.75 in. (19mm) from all moving parts and vibrations.