Finding external leaks
1. Check up liquid level in a tank of the main brake cylinder. A slight decrease in the fluid level can be considered the norm, which is explained by the wear of the brake linings. If there is a noticeable drop in the level, the presence of leaks in the system can be assumed.
2. If the fluid level is unacceptably low, adjust the fluid level.
3. Run the engine to idle.
4. Press a brake pedal with moderate effort. Hold the pedal without increasing effort. If the brake pedal is gradually lowered, there is a leak in the system.
5. Turn off the ignition.
6. Inspect:
- fittings of the main brake cylinder;
- all points of connection of brake pipes and hoses;
- brake pipes and hoses in length;
- brake calipers.
Look for brake fluid leaks, excessive corrosion and/or damage. Pay special attention to the joints of tubes and hoses.
7. While a thin film of fluid around the master cylinder reservoir can be considered normal, the same phenomenon is unacceptable elsewhere in the system. Make any necessary repairs.
Search for internal leaks
1. Run the engine to idle.
2. Apply a light, constant pressure to the brake pedal. Observe the behavior of the pedal.
3. Release the brake pedal and turn off the ignition.
4. If the brake pedal "soft", but the pedal travel is not too large, perform the following operations:
- A) Inspect the brake system for external leaks.
- b) Bleed the brake system.
5. If the brake pedal "tough", but the brake pedal travel is large, perform the following operations:
- A) Loosen the nuts securing the brake master cylinder to the vacuum brake booster.
- b) Carefully separate the brake master cylinder from the booster so that only the bearing surface of the master cylinder can be inspected.
- V) Check the base surface. Look for signs of brake fluid leaks around the primary piston (2).
6. If there is a leak around the primary piston (2) yes, cuffs may be damaged (3) and/or (4) primary piston, repair as necessary or replace the brake master cylinder.
7. If there are leaks in the area of the primary piston (2) no, bleed the brake system.
8. If the brake pedal "tough" and the pedal travel is not excessive, but gradually and constantly increases, repair of the master brake cylinder or replacement of cuffs is required (5) and/or (6) secondary piston (1).
9. If the brake pedal "tough" and the pedal travel is not excessive, but gradually increases and then stabilizes at the same level, then the pressure modulator valve may be leaking, replace the valve.