BMW Coupes and Sedans 1970-1988 Repair Guide

Brake Hoses and Lines

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REMOVAL & INSTALLATION



See Figures 1 and 2

Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

When removing or installing brake line or hoses, always use a backup wrench on the fitting to prevent twisting. Avoid bending the lines or damaging the coating. Use a tubing bender if the line needs to be bent. Use pre-made lines with the flare already constructed. Torque all fittings to 10 ft. lbs. (14.2 Nm).



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Fig. Fig. 1: Use 2 flare-end wrenches to loosen the connection between the brake hose and line



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Fig. Fig. 2: Use a suitable wrench to complete the process and remove the hose

BRAKE LINE FLARING



See Figures 3 and 4

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 most commercially available double-flaring kits. If these instructions differ in any way from those in your kit, follow the instructions in the kit.

  1. Cut the brake line to the necessary length using a tubing cutter.
  2.  
  3. Square the end of the tube with a file and chamfer the edges.
  4.  
  5. Insert the tube into the proper size hole in the bar until the end of the tube sticks out the thickness of the single flare adapter. Tighten the bar wing nuts tightly so the tube cannot move.
  6.  
  7. Place the single flare adapter into the tube and slide the bar into the yoke.
  8.  
  9. Position the yoke screw over the single flare adapter and tighten it until the bar is locked in the yoke. Continue tightening the yoke screw until the adapter bottoms on the bar. This should form the single flare.
  10.  

Make sure the tube is not forced out of the hole in the bar during the single flare operation. If it is, the single flare will not be formed properly and the procedure must be repeated from Step 1.

  1. Loosen the yoke screw and remove the single flare adapter.
  2.  
  3. Position the yoke screw over the tube and tighten until the taper contacts the single flare and the bar is locked in the yoke. Continue tightening to form the double flare.
  4.  
  5. Loosen the screw and remove the bar from the yoke. Remove the tube from the bar.
  6.  
  7. Check the flare for cracks or uneven flaring. If the flare is not perfect, cut it off and begin again at Step 1.
  8.  



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Fig. Fig. 3: Flaring the brake line



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Fig. Fig. 4: Brake line flaring sequence

CHANGING BRAKE FLUID



Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

To ensure continued proper operation of the braking system, the brake fluid must be changed at least every 2 years. If the vehicle is used for heavy duty use, change the fluid at least once a year. If the vehicle is used in competition, bleed the system before and after each event.

Use a quality, name brand Dot 3, or for more extreme conditions a DOT 4 brake fluid. Use fluid from sealed, unused cans. Buy the fluid in quantities that you expect to use. Buying a large container of brake fluid and only using a small portion can lead to the remaining fluid to become contaminated over time. Brake fluid absorbs moisture and can lead to system corrosion and failure.

Always use clean, factory approved brake fluid.

BLEEDING

Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

All Models

See Figure 5

Whenever any hydraulic part of the brake system is removed, the entire system should be bled to remove any air which may have entered.

  1. Fill the master cylinder to the maximum level with the proper brake fluid.
  2.  
  3. Raise and safely support the vehicle on jackstands. Remove the protective caps from the bleeder screws.
  4.  
  5. The proper bleeding sequence always starts with the brake farthest from the master cylinder proceeding to each wheel until you reach the brake closest to the master cylinder.
  6.  

The proper bleeding sequence is: right rear, left rear, right front and left front.

  1. Insert a tight fitting plastic tube over the bleeder screw on the caliper/wheel cylinder and the other end of the tube in a transparent container partially filled with clean brake fluid.
  2.  



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Fig. Fig. 5: Bleeding a brake caliper. Replace the bleeder cover when complete

  1. Depress the brake pedal and loosen the bleeder screw to release the brake fluid. Pump the brake pedal to the stop at least 12 times. Check the tube for air bubbles. If there are no bubbles tighten the bleeder screw.
  2.  

On older vehicles which are not driven regularly, the master cylinder can develop "rough areas". In this case where bleeding the brakes can cause the seals in the master cylinder to tear resulting in the master cylinder needing a rebuild or replacement. As a protective measure, it is recommended that you consult a professional to pressure bleed the brake system, or use a vacuum pump with a bleeder attachment. Vacuum pumps and bleeding kits are available at most automotive parts stores.

  1. Repeat this step on all 4 wheels. When complete, tighten the 7mm bleeders to 3.5 ft. lbs. (5 Nm) Replace the bleeder dust covers if cracked torn or missing. Lower the vehicle and check the brake fluid level.
  2.  

1600, 2000 and 2002 Models
FRONT CALIPERS

Each front caliper must be bled in a specified sequence. Starting with the right front caliper, attach the tube to the bleed nipple at the top front portion of the caliper. Proceed to the nipple at the middle front portion of the caliper, and finally to the nipple at the rear middle portion of the caliper. It is imperative that this sequence be followed.

3 Series Models

Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

3 Series vehicles have only one bleed point on each wheel cylinder and one on each caliper. The calipers may be bled without removing the wheels.

All 6 Cylinder Models Except 528e and 733i

Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

These models have disc brakes at the rear. Bleed points for these calipers are at the top of the inside. when bleeding front calipers, follow this bleeding sequence;

  1. Front top nipple.
  2.  
  3. Rear middle nipple.
  4.  
  5. Front middle nipple.
  6.  

528e Models

Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

The 528e has only one bleeder screw on each caliper, front and rear. The calipers may be bled without removing the wheel.

733i Models

Models equipped with anti-lock brakes require expensive and specialized equipment to bleed the brake system. If you do not own or have access to this equipment, it is best to have a properly equipped professional perform this procedure.

Bleed points for these calipers are located at the top inside portion of the caliper and the top outside portion of the caliper. When bleeding the calipers, start at the inside nipple, then proceed to the outside nipple. Always install the rubber bleeder cap when finished.

 
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