Owners of cars equipped with vacuum braking systems are puzzled by this question. If the fluid level in the reservoir begins to drop frequently, it is necessary to inspect the entire brake system for leaks.
Check reservoir, brake lines, hoses and fittings for leaks. Look underneath the machine for brake fluid leaks. Inspect rubber, discs and wheel pads. Pay particular attention to the condition of the brake pads. If they are worn out, this can lead to increased brake fluid consumption. Also check the condition of the wheel brake cylinder seals. If they are worn, the removed wheels show signs of fluid leakage. Start the car, put the gear lever in neutral, and then press and hold the brake pedal with the engine idling. If there is a fluid leak in the hydraulic brake system, the pedal will gradually fail. If the pedal immediately reaches the floor when you press it, therefore, the brake circuit is out of order. Inspect the hydraulic brake system. If no external fluid leaks are found, then there are problems with the cuffs in the master cylinder. If the search does not return any results, the brake fluid is likely to leak through the master cylinder rod into the vacuum brake booster. Unscrew the master cylinder mounting nuts, pull it out. from the vacuum cleaner and inspect for leaks. If a brake fluid is found inside the vacuum cleaner, it is necessary to change the brake cylinder. Make sure that the master cylinder is working, there should be no casting cracks, deformation or swelling of the cylinder and piston gaskets. If the rubber elements are damaged, disassemble the hydraulic system and flush all parts with alcohol, cleaning them from contamination. Install new hoses and gaskets. Replace the brake pads if brake fluid is found on them. Assemble the system and fill it with liquid. Bleed the system by raising the vehicle and remove the bleed cap from the right rear wheel. Put a tube on the fitting and lower it into a transparent vessel. Ask an assistant to press the brake pedal several times. Tighten the fitting after the air is released and the old brake fluid is drained (it is usually darker than fresh). The fitting must be tightened with the brake pedal depressed. Repeat this procedure for the left rear wheel, then for the right front and left front wheels.
