Volkswagen Front Wheel Drive 1974-1989 Repair Guide

Filling and Bleeding

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CAUTION
The hydraulic modulator is capable of self-pressurizing and can generate pressures above 3000 psi anytime the ignition switch is turned ON. Relieve the system pressure before servicing the hydraulic system. Improper repair or test procedures can cause serious or fatal injury.

FILLING THE SYSTEM



The reservoir on the hydraulic modulator is filled in the usual manner with no special procedures being necessary. Always wipe the cap and surrounding area clean of dirt and debris before opening the reservoir; the smallest bit of dirt may impair the operation of the system. When adding fluid, fill the reservoir only to the MAX line on the reservoir; do not overfill.

Only DOT 4 brake fluid must be used; silicone or DOT 5 fluid is specifically prohibited. Do not use any fluid which contains a petroleum base; these fluids will cause swelling and distortion of the rubber parts within the system. Do not use old or contaminated brake fluid. Do not reuse fluid which has been bled from the system.

BLEEDING THE SYSTEM



Bleeding may be performed using either a pressure bleeder or the manual method. In either case an assistant will be required to depress the brake pedal. Extreme cleanliness must be observed at all times. If using the manual method, the fluid reservoir must be filled to the upper edge before bleeding begins. Do not allow the fluid level to drop below the MIN mark at any time. Do not reuse fluid released during bleeding.

Front Brakes
  1. Turn the ignition switch OFF .
  2.  
  3. Relieve the brake system pressure, as described earlier in this section.
  4.  
  5. If using pressure bleeder equipment, connect it to the brake fluid reservoir and switch it on.
  6.  
  7. Connect a tight-fitting vinyl hose to the bleeder port of the caliper. If using pressure bleeding equipment, begin at the left front caliper. If using the manual method, begin on either side. Immerse the other end of the hose in a container of clean brake fluid.
  8.  

Use of a cap or cover on the container is recommended. The brake fluid may bleed with enough force to splash out of an open container.

  1. Open the bleeder screw. Have an assistant depress the brake pedal slowly until the fluid flows without bubbles.
  2.  
  3. Close the bleeder screw before the pedal is released.
  4.  
  5. Remove the vinyl tube from the caliper. Inspect and top off the fluid supply in the reservoir if necessary.
  6.  
  7. Repeat the procedure at the opposite wheel.
  8.  

Rear Brakes
  1. Turn the ignition switch OFF .
  2.  
  3. Relieve the brake system pressure, as described earlier in this section.
  4.  
  5. If using pressure bleeder equipment, connect it to the brake fluid reservoir and switch it on.
  6.  
  7. Connect a tight-fitting vinyl hose to the bleeder port of either caliper. Immerse the other end of the hose in a container of clean brake fluid.
  8.  

Use of a cap or cover on the container is recommended. The brake fluid may bleed with enough force to splash out of an open container.

  1. Open the bleeder screw. Have an assistant turn the ignition switch ON .
  2.  
  3. Press the lever of the proportioning valve towards the axle until brake fluid flows out without bubbles. Release the lever and close the bleeder screw.
  4.  

Running time of the ABS pump must not exceed 120 seconds at any one time. If this time is approached or exceeded, a minimum of 10 minutes cooling time is required before proceeding. Do not allow the fluid level to fall below the MIN line at any time.

  1. Switch the ignition OFF while transferring equipment. Remove the vinyl tube from the caliper. Inspect and top off the fluid supply in the reservoir if necessary.
  2.  
  3. Repeat the procedure at the opposite wheel.
  4.  
  5. Once both rear calipers are bled and the service equipment removed, switch the ignition ON until the pump shuts off.
  6.  
  7. Fill the brake fluid reservoir to the MAX line.
  8.  



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Fig. Fig. 1: Brake Specifications

 
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