Caution! Regularly check the brake fluid level in the master cylinder reservoir. The brake fluid level should be slightly below the MAX mark of the master cylinder supply reservoir.
A drop in the fluid level indicates either a leak in the brake fluid system or excessive wear of the brake pads. If the low brake fluid light comes on on the instrument panel, do not rush to top it up immediately, first check the thickness of the brake pad linings: maybe it is 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 reservoir seems clean enough to them, and this is 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, pipes and, as a result, leads to premature failure of brake system components, but also significantly reduces the boiling point of the brake fluid.
Normal boiling point of the brake fluid "Neva" — 190°C, "Tom" — 210°C, "Dew" — 260°C. During frequent heavy braking, the front wheel disc brakes become very hot and if the water content is too high, the brake fluid can boil, which usually leads to brake failure.
Advice: To avoid unexpected expenses in the future, it is better to replace the fluid in the brake system in a timely manner.
Bleeding the brake system
If the brake pedal becomes "soft" and becomes "harder" after several consecutive presses, this indicates the presence of air in the hydraulic brake drive.
To remove air from the system, you need to bleed the brakes. The procedure for bleeding the brakes is quite simple, but it is more convenient to do it together.
1. Make sure the reservoir on the master cylinder is full.
2. Clean the bleed nipple on one of the rear brakes from dirt and put a rubber hose of the appropriate diameter on the nipple.
3. Place the end of the hose in a clear container containing a small amount of brake fluid.
4. Have an assistant press and hold the brake pedal several times.
5. Loosen the nipple slightly with a wrench until the pedal "falls through" and liquid with air bubbles starts flowing out of the hose.
6. Without releasing the pedal, tighten the nipple. Repeat the procedure until the release of bubbles stops.
7. After bleeding the rear wheel brake, bleed the front wheel brake of the same circuit in the same way.
Warnings!
- The VAZ-21099 car uses a diagonal brake drive, i.e. if you have bled the rear right wheel, then bleed the front left.
- When bleeding the brake system, do not forget to periodically check the brake fluid level in the master cylinder reservoir and top it up if necessary.
Checking the brake system
1. The reason for the loss of braking efficiency may be poor operation of the vacuum booster. To quickly check it, press the brake pedal several times with the engine off to "remove the vacuum" from the booster, and then, holding the pedal, start the engine.
Is the brake pedal slightly depressed?
No: see point 3.
2. The vacuum booster is in good condition. See item 6.
3. Check the integrity and reliability of the hose connecting the vacuum booster to the engine intake manifold.
Is the hose OK?
No: see point 5.
4. The vacuum booster needs to be replaced.
5. Replace or repair the hose.
6. If braking is accompanied by beating and pulsation of the brake pedal, you should first check the condition of the front disc brakes.
7. After jacking up the car, remove the front wheel and inspect the brake disc. The thickness of the brake disc should be at least 10.8 mm. The disc surface should be flat and smooth on both sides.
8. If the disk surface is covered with rust in places, which usually happens after a long parking of the car with un-dried brakes, try to clean the working surface with a fine emery cloth. If this procedure does not help, you will have to send the disks for grinding or replace them with new ones.
9. Check the mobility of the brake pads. To do this, use a screwdriver to try to move the pads away from the brake disc. If the pads cannot be moved apart, this means that the piston in the brake cylinder is "stuck".
Warning! Jamming of the brake cylinder piston results in constant braking of the corresponding wheel when the pedal is released and skidding of the car when braking.
10. The parking brake operates the rear brakes with a cable that connects the parking brake lever and the brake shoe control mechanism. Many drivers try to use the "handbrake" as little as possible to extend its life, and achieve the opposite result. If you do not use the parking brake, dirt and moisture stagnate in the cable sheaths, the cable becomes covered with rust, stops moving and at one "fine" moment breaks. Therefore, use the "handbrake" to your heart's content, but do not forget to adjust its drive from time to time.
11. To adjust the parking brake, lift the lever up four or five clicks on the ratchet mechanism. While under the car, loosen the tensioner lock nut and use the adjusting nut to tighten the cable.
Tip: After adjustment, check if the rear wheels rotate freely. If they rotate stiffly, loosen the adjusting nut a little and secure it with the lock nut.