VW Technical Articles

How to replace Master Cylinder

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Does your pedal slowly sink to the floor when you push on your brakes? Have you checked your brake lines and wheel cylinders for leaks and found none? Do you notice the level of brake fluid in your reservoir dropping after relatively few miles of driving? If so you probably need to replace your master cylinder. You will need:

  • Master cylinder
  • DOT4 brake fluid
  • Wrench 11, 13, 19 & 22mm
  • Bulb syringe
  • Rag
  • Jack

  • Drain brake fluid reservoir using a bulb syringe.
  • Jack up your car and remove front left wheel.
  • Master cylinder is mounted on the firewall near central tunnel (see pics 1 and 2, red arrow). Place a piece of card board and a rag under the master cylinder to catch any brake fluid that might run out of the lines.

  • Ok, we're looking at picture #3. Using 11mm wrench, disconnect front (1 & 2) and rear (3) brake lines. Unplug the wires or plugs that go to the stop light switch/switches. 66 and earlier bugs have 1 stop light switch, 67 and later bugs have 2 since they started using a dual circuit master cylinder. Remove switches using 22mm wrench. Pull out plastic fittings, 6 and 7.
  • Move to the inside of the car and remove the two 13mm bolts that hold the master cylinder in place, picture 4. The old master cylinder can now be removed.
  • Take your brand new master cylinder and bleed it.
  • To install, bolt the master cylinder to the frame. Do not forget spacers on the Type 1.
  • Lubricate the elbows with the brake fluid and insert them into the rubber seals
  • If necessary, adjust the brake pedal free travel.
  • Refill the master cylinder reservoir and bleed the brakes.


brakes, master cylinder