GM Full Size Vans 1987-1997 Repair Guide

Brake Hoses and Lines


Metal lines and rubber brake hoses should be checked frequently for leaks and external damage. Metal lines are particularly prone to crushing and kinking under the vehicle. Any such deformation can restrict the proper flow of fluid and therefore impair braking at the wheels. Rubber hoses should be checked for cracking or scraping; such damage can create a weak spot in the hose and it could fail under pressure.

Any time the lines are removed or disconnected, extreme cleanliness must be observed. Clean all joints and connections before disassembly (use a stiff bristle brush and clean brake fluid); be sure to plug the lines and ports as soon as they are opened. New lines and hoses should be flushed clean with brake fluid before installation to remove any contamination.


See Figures 1 through 4

  1. Disconnect the negative battery cable.
  3. Raise and safely support the vehicle on jackstands.
  5. Remove any wheel and tire assemblies necessary for access to the particular line you are removing.
  7. Thoroughly clean the surrounding area at the joints to be disconnected.

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Fig. Fig. 1: Use a brush to clean the fittings of any debris

  1. Place a suitable catch pan under the joint to be disconnected.
  3. Using two wrenches (one to hold the joint and one to turn the fitting), disconnect the hose or line to be replaced.

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Fig. Fig. 2: Use two wrenches to loosen the fitting. If available, use flare nut type wrenches

  1. Disconnect the other end of the line or hose, moving the drain pan if necessary. Always use a back-up wrench to avoid damaging the fitting.
  3. Disconnect any retaining clips or brackets holding the line and remove the line from the vehicle.

If the brake system is to remain open for more time than it takes to swap lines, tape or plug each remaining clip and port to keep contaminants out and fluid in.

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Fig. Fig. 3: Any gaskets/crush washers should be replaced with new ones during installation

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Fig. Fig. 4: Tape or plug the line to prevent contamination

To install:
  1. Install the new line or hose, starting with the end farthest from the master cylinder. Connect the other end, then confirm that both fittings are correctly threaded and turn smoothly using finger pressure. Make sure the new line will not rub against any other part. Brake lines must be at least 1/2 in. (13mm) from the steering column and other moving parts. Any protective shielding or insulators must be reinstalled in the original location.

Make sure the hose is NOT kinked or touching any part of the frame or suspension after installation. These conditions may cause the hose to fail prematurely.

  1. Using two wrenches as before, tighten each fitting.
  3. Install any retaining clips or brackets on the lines.
  5. If removed, install the wheel and tire assemblies, then carefully lower the vehicle to the ground.
  7. Refill the brake master cylinder reservoir with clean, fresh brake fluid, meeting DOT 3 specifications. Properly bleed the brake system.
  9. Connect the negative battery cable.


See Figures 5 and 6

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Fig. Fig. 5: Single and double flares

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Fig. Fig. 6: Using a pipe flaring tool

Use only brake line tubing approved for automotive use; never use copper tubing. Whenever possible, try to work with brake lines that are already cut to the length needed. These lines are available at most auto parts stores and have machine made flares, the quality of which is hard to duplicate with most of the available inexpensive flaring kits.

When the brakes are applied, there is a great amount of pressure developed in the hydraulic system. An improperly formed flare can leak with resultant loss of stopping power. If you have never formed a double-flare, take time to familiarize yourself with the flaring kit; practice forming double-flares on scrap tubing until you are satisfied with the results.

The following procedure applies to the SA9193BR flaring kit, but should be similar to commercially available brake-line flaring kits. If these instructions differ in any way from those in your kit, follow the instructions in the kit.

  1. Determine the length necessary for the replacement or repair and allow an additional 1 / 8 in. (3.2mm) for each flare. Select a piece of tubing, then cut the brake line to the necessary length using an appropriate saw. Do not use a tubing cutter.
  3. Square the end of the tube with a file and chamfer the edges. Remove burrs from the inside and outside diameters of the cut line using a deburring tool.
  5. Install the required fittings onto the line.
  7. Install SA9193BR, or an equivalent flaring tool, into a vice and install the handle into the operating cam.
  9. Loosen the die clamp screw and rotate the locking plate to expose the die carrier opening.
  11. Select the required die set (4.75mm DIN) and install in the carrier with the full side of either half facing clamp screw and counter bore of both halves facing punch turret.
  13. Insert the prepared line through the rear of the die and push forward until the line end is flush with the die face.
  15. Make sure the rear of both halves of the die rest against the hexagon die stops, then rotate the locking plate to the fully closed position and clamp the die firmly by tightening the clamp screw.
  17. Rotate the punch turret until the appropriate size (4.75mm DIN) points towards the open end of the line to be flared.
  19. Pull the operating handle against the line resistance in order to create the flare, then return the handle to the original position.
  21. release the clamp screw and rotate the locking plate to the open position.
  23. Remove the die set and line, then separate by gently tapping both halves on the bench. Inspect the flare for proper size and shape. Dimension A should be 0.272-0.286 in. (6.92-7.28mm).
  25. If necessary, repeat Steps 2-12 for the other end of the line or for the end of the line which is being repaired.
  27. Bend the replacement line or section using SA91108NE, or an equivalent line bending tool.
  29. If repairing the original line, join the old and new sections using a female union and tighten.