Attention! Regularly check the brake fluid level in the master cylinder reservoir. The level must be at the mark «MAX» or just below the brake master cylinder reservoir.
Attention! A drop in fluid level indicates either a leak of brake fluid from the system or excessive wear on the brake pads. If a lamp lights up in the instrument cluster, indicating a low level of brake fluid, do not rush to top it up immediately, first check the thickness of the brake pads: maybe it's time to replace the pads?
Car manufacturers recommend replacing all brake fluid in the system after a certain period. Some drivers ignore this advice because the fluid in the tank seems clean enough to them, and it’s completely in vain. The fact is that brake fluid is very hygroscopic - it absorbs moisture from the air, and this moisture over time not only destroys the surfaces of brake cylinders, pipelines and, as a result, leads to premature failure of brake system components, but also significantly reduces the boiling point brake fluid. Normal boiling point of brake fluid «Neva» – 190°С, «Tom» – 210°С, «Dew» – 260°С. With frequent heavy braking, the front wheel disc brakes become very hot and with a high water content, the brake fluid can boil, which usually leads to brake failure.
Note. In order not to expose yourself in the future to unforeseen expenses for repairing not only the brake system, but the entire car, it is better to change the fluid in the brake system in a timely manner.
If the brake pedal has become «soft», and with several successive clicks it becomes «harder», which means that air has entered the hydraulic brake actuator. It could get into the system during its repair, replacement of brake fluid, depressurization of the system if pipes and hoses are damaged, or a drop in the level of brake fluid in the reservoir of the main brake cylinder.
To remove air from the system, it is necessary to bleed the brakes according to the method described in Sec. «Brake system» (see «Bleeding the hydraulic drive of the brake system»).
The reason for the loss of braking efficiency may be the unsatisfactory operation of the vacuum booster.
For its express check, press the brake pedal several times with the engine off to remove the vacuum in the amplifier, and then, while holding the pedal, start the engine. If after starting the engine the pedal drops a little, the vacuum booster is working.
1. If the pedal remains motionless, check the integrity and reliability of the connection of the vacuum booster hose to the fitting on the engine intake pipe...
2....and with a non-return valve. Replace or repair defective hose. If the hose is good, the vacuum booster needs to be replaced (see «Removal and installation of the vacuum amplifier of brakes»).
If braking is accompanied by a beating and pulsation of the brake pedal, you should first check the condition of the front disc brakes.
3. Having established the car on a jack, remove a forward wheel and examine a brake disk. The thickness of the brake disc must be at least 17.8 mm. The surface of the disc must be even and smooth on both sides. If the surface of the disc is covered with rust in places, which usually happens after a long parking of the car with dry brakes, try cleaning the working surface with a fine emery cloth. If this procedure does not help, you will have to give the discs for grinding or replace them with new ones.
4. Check the mobility of the brake pads. To do this, use a screwdriver to try to take the pads away from the brake disc. If the pads cannot be separated, then the piston is stuck in the brake cylinder.
Attention! Jamming of the piston of the brake cylinder leads to the constant braking of the corresponding wheel when the pedal is released and the car skids when braking.
Note. The parking brake actuates the rear brakes by a cable connecting the parking brake lever and the brake shoe control mechanism. Many drivers try to use the parking brake as little as possible in order to prolong its life, and achieve the opposite result. If you do not use the parking brake, dirt and moisture stagnate in the sheaths of the cable, the cable becomes rusty, stops moving and breaks. Therefore, use the parking brake whenever necessary, but do not forget to adjust its drive from time to time.
According to the manufacturer, the parking brake lever travel should be:
- when adjusting 2-4 clicks;
- in operation 2–8 clicks.
A properly adjusted parking brake should hold the vehicle on a 25% grade.
If the lever is raised more than 8 clicks when the vehicle is braked with the parking brake, the vehicle will not be held on a slope. If the lever travel is less than 2 clicks, the wheels may be partially blocked while the vehicle is moving. In both cases, the parking brake must be adjusted according to the procedure described in Sect. «Maintenance» (see «Checking and adjusting the parking brake drive»).