Removing And Installing Brake Master Cylinder

Porsche 928 Axle

Removing

1. Remove intake hoses and air cleaner upper section.

2. Drain both chambers of brake fluid reservoir by pumping out brake fluid via pertinent bleeder screws depending on brake circuit division.

Diagonal brake circuit division up to 1983 models. Axle brake circuit division since 1984 models.

Identification: stepped master cylinder and screw-in brake pressure regulator (see point 5).

5. Detach brake lines. Up to 1983 models,

Counterhold on hexagon of regulator when unscrewing rear axle brake line on screw-in brake pressure regulator. Screw-in regulator of cars with ABS is installed on hydraulic unit.

Porsche 928 Brake Booster Check Valve

4. Pull brake fluid reservoir out of master cylinder from above. If applicable, pull off plugs on hydraulic stop light switches.

3. Detach vacuum hose with check valve at brake booster.

Pull off vacuum line on branch, plug for warning device and hose for clutch control.

4. Pull brake fluid reservoir out of master cylinder from above. If applicable, pull off plugs on hydraulic stop light switches.

Since 1984 models

Counterhold on hexagon of regulator when unscrewing rear axle brake line on screw-in brake pressure regulator. Screw-in regulator of cars with ABS is installed on hydraulic unit.

6. Remove the master brake cylinder at its flange with a 1/4-inch ratchet, a 13 mm socket wrench insert and a suitable extension. Take out the master brake cylinder.

Note

On right-hand drive cars, the windshield washer filler pipe must also be removed. Take it out at the same time as the master brake cylinder.

Installing

1. Renew the O-ring between the master brake cylinder and the brake booster, or else a loss of vacuum may occur.

2. Install the master brake cylinder and connect up the brake pipes.

3. Press the fluid reservoir into the sealing plugs in the master brake cylinder. Use new sealing plugs each time the fluid reservoir is removed. When pressing in, the reservoir must pass 2 detents before firm seating can be guaranteed.

Note

Use only brake fluid or brake cylinder paste as an aid to installation. Substances containing mineral oil will destroy the rubber elements in the brake system and cause brake failure. In the case of stepped brake master cylinders, there is a washer under the front sealing plug (intermediate piston brake circuit).

4. Bleed the brake/clutch with the filling and bleeding device. Check for leaks and for correct operation.

Porsche 928 Fuel Pump InstallationPorsche 928 Brake Booster Removal

928 Brakes/Hydraulic Parts (Regulators, Booster) 47

5.Remove cover and unscrew mounting nuts of brake booster.

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