Note. A failed GTZ must be replaced. Manufacturers do not recommend attempting to rebuild the brake master cylinder.
Withdrawal
1. The brake master cylinder is located in the engine compartment of the vehicle and is attached to the brake booster assembly.
2. Pump out as much liquid as possible from the GTZ tank (use a syringe or rubber bulb).
3. Place a rag under the fittings and prepare caps or plastic bags to seal the open ends of the brake lines to prevent dirt from entering the system.
Attention! Brake fluid is one of the aggressive chemical compounds and, in contact with body panels, destroys the paintwork. Before proceeding with the procedure, cover the wings and front panel of the car with special covers, or just old blankets.
4. Loosen the nuts of the fitting units for connecting to the GTZ of the brake lines (see accompanying illustration). To avoid rounding of the splines of the nuts, use a special box wrench with a split head to loosen them.
5. Slightly pulling outwards, separate the brake lines from the master cylinder fittings. Seal the open ends of the tubes immediately.
6. Disconnect the wiring connector of the brake fluid level sensor-switch on the GTZ housing, then loosen the two fixing nuts and separate the master cylinder from the brake booster assembly. Remove the cylinder from the mounting studs and remove it from the engine compartment (take care not to spill the cylinder-filling hydraulic fluid onto the painted body panels).
Installation
1. Before installation, a new GTZ must be pumped on a workbench. For convenience, clamp the cylinder seat flange in a vice with soft jaws (see illustration below) - Next, you will have to simultaneously manipulate the piston in the cylinder and observe the flow of brake fluid pushed out through the outlet.
2. Connect a pair of tubes from the special bleed kit to the GTZ outlet fittings (ask at car accessories stores) (see accompanying illustration).
3. Fill the reservoir with fresh brake fluid of the correct grade (see chapter Current service).
4. Slowly push the pistons into the cylinder (It is best to use a large Phillips screwdriver). Air should begin to escape from the pressure chambers into the reservoir. At the same time, it is important that the ends of both tubes are completely immersed in the brake fluid in the reservoir in order to exclude the possibility of sucking it back into the cylinder when the pistons are released.
5. Continue pumping until the fluid pushed through the tubes is completely free of air bubbles.
6. Disconnect the tubes one by one, plugging the open ends of the fittings immediately. Close the GTZ tank with a lid.
7. Put the GTZ on the studs on the vacuum booster assembly and, so far only by hand, tighten the fixing nuts.
8. Screw the fittings of the brake lines into the cylinder. Since the cylinder is not yet completely fixed, its position can be slightly corrected in order to facilitate the screwing in of the fittings - try not to strip the threads.
9. Tighten the GTZ fastening nuts with the required force, tighten the union connections tightly.
10. Fill the GTZ reservoir with fresh brake fluid and bleed the brake system (see Bleeding the brake system). For pumping the GTZ on a car (if you haven't done it on a workbench) you will need the help of an assistant who will manipulate the foot brake pedal. Ask an assistant to depress the pedal several times, then fix it in the lower position. Loosen the union nut, releasing the mixture of air and brake fluid from the cylinder. Repeat the procedure until the ejected fluid is completely free of air bubbles. Proceeding in a similar manner, pump the second fitting.
11. Before starting the operation of the car, make sure that the brakes are working properly.