Vanagon Repair: Brake Master Cylinder

My brake master cylinder failed and I decided to tackle this replacement myself. I sourced the replacement master cylinder from GoWestyAutoParts.com for $46 plus shipping. While this isn't a German-made or OEM replacement, it is a well-reviewed, high quality Italian-made part.

I'm grateful for the step-by-step guidance in a very helpful post on vanagonauts.com.  It's clear and thorough and the only weakness I found is that it lacked pictures. I'm more or less re-posting that guide below, adding or omitting details per my experience, with images from my recent removal/installation.

Brake master cylinder and fluid reservoir after removing the instrument panel

Tools:

• Phillips #2 and two flat-head screwdrivers (optional)
• 7 mm wrench to loosen and tighten brake bleeders
• 13 mm socket/ratchet with 10" extension
• 11 mm open end wrench for the brake line
• 22 mm wrench to replace the brake light switches (or one big crescent wrench)

Supplies:

• 2 pints of DOT 4 brake fluid
• Rags
• 2 pints of rubbing alcohol

Step 1. Removing the Instrument Panel
Pull off the cover over the instrument cluster.Remove the 4 Phillips head screws. Reach behind the speedometer cluster and squeeze the plastic retainer holding the cable in and release that. This gives you more play in the instrument panel to unplug the main cable cluster. To be safe you should disconnect the battery when playing with the wiring (admittedly, I didn't).Then pull all switches, plugs, and wiring. With everything removed you'll find the master cylinder exposed with the plastic reservoir occupying most of the space.

Step 2. Draining the Reservoir of Brake Fluid
Put a hose and bottle on the bleeder of the left front caliper and open the bleeder while pumping the brakes. This worked well and drained all the fluid.

Step 3. Removing the Clutch Master Cylinder Filler Tank Hose (for MANUAL Vanagons)  

After removing the filler tank hose

On the upper right side of the tank there is a pipe leading to a fitted 3/8" braided rubber hose going to the clutch master cylinder that needs to be worked off. Put a rag under to collect any fluid here. I was able to simply work it off without any tools or prying. If that's not possible, try using a pair of pliers to gently start twisting the hose. Flat screwdrivers may also help to pry it off. Be careful doing this because if you break the plastic pipe within the hose, you will need a whole new reservoir. After it's free, plug the hose prevent any brake fluid from leaking out while working.

Step 4. Removing the Brake Lines
Have a rag under both of the brake line to catch any drips drip. If you pumped the fluid out (Step 2) there should be minimal amounts easily captured on a rag. Loosen the two metallic brake lines going to the front and rear brake circuits. One brake line is on the center right side  and the other brake line is on the closer end of the master cylinder sticking out at you. The nuts are 11 mm.

Step 6. Removing the Old Brake Master Cylinder
With the two break lines and braided hose removed, all you have left is the two, 13 mm master cylinder anchor nuts. Use your ratchet and 10" extension to get at them, located at the back of the master cylinder, deep into the dash. A magnetic ratchet or wand is helpful to catch the nuts. Finally, disconnect the brake light

New brake master cylinder and old

wiring from the two switches on the bottom of the master cylinder and take it away.

Step 7. Prepping the New Master Cylinder for Installation
Switches: You may want to replace your brake light switches at this time. I should have, but didn't have replacement and didn't want to delay the job any further. I simply installed the old switched on the new master cylinder.

Detail of original VW brake master cylinder

Filler tank: Remove the plastic brake fluid reservoir from the master cylinder by by prying it from the rubber grommets. If yours, like mine, is full of brake line crud, you should clean that out. Rubbing alcohol works really well. Swish the alcohol around in the reservoir until the grime washes away. Wait a bit for the alcohol to evaporate before snapping the reservoir onto the new cylinder. Make sure there is a new seal (which should have come with your new cylinder) between the master cylinder and the brake booster.

New master cylinder positioned for installation

Step 8. Installing the New Brake Master Cylinder
Angle the new master cylinder (and reservoir) over the pushrod coming out of the booster. Ensure that the pushrod inserts into the master cylinder shaft. Loosely apply the 13mm anchor bolts. Connect the brake lines, ensure that the threads are aligned, and tighten them down. Connect the braided rubber hose. Tighten down the anchor nuts. Fill the reservoir with new DOT 4 brake fluid and pump the brakes a few times to
get fluid into the system.

Step 9 Bleeding the Brakes
It is absolutely imperative to get all the air out of the brake circuit. Otherwise, the brakes will be mushy and not operate efficiently. To bleed the brakes, you need an assistant. While you lay under the van at the rear passenger side wheel, have your friend/assistant apply slow, steady pressure to the brake pedal and HOLD it 3/4 of the way to the floor. BEFORE he releases the pedal, close the bleeder valve. Repeat the procedure until the flow of brake fluid is clear and shows no sign of air bubbles. Proceed to next bleeder valve. Repeat the process once you have cycled through each bleeder. Watch the fluid in the reservoir to ensure continuous level of brake fluid.  If it drops below the "min" line, you'll introduce air to the circuit! You MUST follow this bleed order:

• Right Rear
• Left Rear
• Right Front
• Left Front

Good luck!