How to Install the Master Cylinder on a 1986 Volkswagen Jetta

The master cylinder is the key component for safe operation of the braking system on your Jetta. This component converts the energy from the driver's leg pushing on the brake pedal into hydraulic pressure to squeeze the brake calipers. Replacement of the master cylinder may be required from failure to produce sufficient pressure or a hydraulic fluid leak. Failure of the master cylinder can result in loss of half or all of the braking system. Any indication of an issue with this part should be treated as an urgent need for service.

Tools Used: Combination metric wrenches, Line wrenches, Ratchet, Metric sockets, Extension, Brake fluid, Second person for bleeding the brakes

Install Master Cylinder

Set the emergency brake to keep the vehicle from moving. Remove the negative terminal from the battery using a metric wrench.

Disconnect the electrical connector from the master cylinder by firmly pulling the connector.

Use a line wrench to disconnect the front and rear brake lines from the master cylinder.

Remove the two nuts securing the master cylinder to the brake booster using a ratchet, extension and proper-sized metric socket.

Remove the master cylinder by pulling it towards the front of the car to clear the mounting studs on the brake booster. Lift the master cylinder out of the engine bay, being careful not to spill any brake fluid.

Place the new master cylinder on the mounting studs protruding from the brake booster. Tighten the two mounting nuts with the ratchet, extension and socket.

Reattach the front and rear brake lines to the new master cylinder. Tighten the lines with the line wrench to avoid rounding the line fittings.

Plug the electrical connector into the side of the new master cylinder.

Remove the reservoir cap from the top of the new master cylinder and pour brake fluid up to the maximum fill line.

Bleed the brake system to remove the air from the brake lines, calipers and master cylinder. Have another person sit in the driver's seat and hold the brake pedal down while you turn the brake caliper bleeding screw a quarter turn counterclockwise. When the fluid stops squirting from the bleeding screw, tighten it. Continue this process until the fluid coming out is free of air bubbles. Check the master cylinder reservoir and top it off with brake fluid.

Repeat Step 10 for each of the remaining three wheels.

Top off the master cylinder with fluid. Replace and secure the reservoir cap on the new master cylinder.

Replace the negative cable on the battery and tighten it with the metric wrench. Release the emergency brake and test-drive the vehicle.

Tips & Warnings

Avoid spilling brake fluid onto painted surfaces as it will remove paint.

If braking problems persist after replacing the master cylinder, consult a professional mechanic.

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