Fill the hydraulic drive only with special brake fluid according to the lubrication table in the following order:

1. Check the tightness of all hydraulic connections and the condition of the flexible hoses.

2. Raise the hood (remove the radiator lining on a car of the UAZ-3741 family) and unscrew the covers of the master cylinder tanks. Fill the reservoirs with brake fluid.

UAZ-3151 service brake drive

Fig 1 . UAZ-3151 working brake system drive</ p>

3. Remove the rubber cap from the bypass valve of the brake cylinder of the right rear brake mechanism and put a rubber hose about 400 mm long on the valve.

Dip the other end of the hose into a glass vessel with a capacity of at least 0.5 liters filled with brake fluid (Fig. 2).

Bleeding the brake system

4. Loosen the bypass valve ½ - ¾ turn, then press the pedal several times.

Depress the pedal quickly, release slowly.

Fluid pressurized by the brake master cylinder piston will fill the hydraulic actuator and displace air.

Bleed until air bubbles stop coming out of the hose lowered into the vessel with brake fluid.

During bleeding, add brake fluid to the reservoirs of the master brake cylinder, making sure that the bottom is not exposed so that air does not enter the system again.

During the entire filling operation, keep the end of the hose immersed in the liquid.

UAZ-3741 service brake drive

Fig 3. UAZ-3741 service brake drive

5. Tightly turn the bypass valve of the wheel cylinder with the pedal depressed, remove the hose and put on the cap.

Bleed the hydraulic drive not only when filling it with liquid, but also in case of depressurization of the hydraulic drive of the working cylinder of the rear brake mechanisms

6. Bleed the brake cylinder of the rear left brake mechanism, then the pressure regulator and the brake cylinders of the front brake mechanisms.

On the brake mechanisms of the front wheels, first the lower and then the upper cylinder is pumped.

7. Turn off the alarm device, for which do the following:

- unscrew the bypass valve of the right or left working cylinder of the rear brake mechanisms;

- gently press the pedal until the signal lamp on the instrument panel turns off; if the signal lamp flashes, this will mean that the signaling device pistons have passed the neutral position, and therefore the operation must be repeated from the beginning, but only by unscrewing the front wheel bypass valve;

- close the valve while pressing the pedal.

After bleeding all the brake mechanisms, add fluid to the reservoirs of the main brake cylinder to a level 15–20 mm below the upper edges of the filler holes.

Tighten the lids tightly.

Do not top up the brake master cylinder with liquid collected in a glass vessel during pumping. If the brake fluid in the system is dirty, drain it and fill the system with fresh fluid.

Do not press the pedal with the brake drum removed, as the pressure in the hydraulic drive will force the pistons out of the wheel cylinders and fluid will flow out.

After filling the system with fluid, check the vehicle for braking.

With the correct adjustment of the service brake mechanisms and the correct bleeding of the hydraulic drive, full braking should occur within ½ - 2/3 of the pedal travel, after which the foot should feel a “hard” pedal.