The pneumatic brake booster (Fig. 1) is designed to convert the energy of compressed air into the required pressure of the working fluid in the hydraulic part of the brake drive

To improve the reliability of the brakes, Ural vehicles are equipped with two power amplifiers, which are installed on the outside of the left side member under the cab.

The front pneumatic booster actuates the service brakes of the wheels of the front and middle axles, the rear - the service brakes of the wheels of the rear axle.

When you press the brake pedal, the valve in the brake valve opens, and air enters through the pipeline under the pneumatic booster pistons.

Under air pressure, the rod with pistons moves and through the pusher acts on the piston of the main brake cylinder, which displaces fluid into the brake line.

When braking, the air from the pneumatic booster is released into the atmosphere through the brake valve.

The pistons of the main brake cylinder and the pneumatic booster return to their original position under the action of the springs.

Pneumatic boosters should be removed from the car and disassembled only for maintenance and troubleshooting (replacement of worn cuffs, etc.).

When removing the pneumatic boosters from the car, disconnect the pipelines of the brake and sealing systems from them and the main brake cylinders, as well as the wires from the sensors of the “Brake” signal lamp.

Remove the mounting bolts to the frame side member and remove the pneumatic boosters.

Disassembly of pneumatic amplifiers

Drain the brake fluid, unscrew and remove the reservoir 4, unscrew the nuts, remove the ties 22 and the rear pneumatic cylinder 19.

Remove the hose, piston assembly with rod 23, spacer 16 and pusher 8.

Unlock and unscrew the bolts 29, remove the locking plates 30, the front pneumatic booster cylinder 9 as an assembly with the cover 31 and the gasket.

Remove retaining ring 27, washer 28 and remove piston 6 as an assembly with outer seal 7. Remove ring 33, inner seal 34 and spring 36 as an assembly with check valve 38.

It is not recommended to unscrew plug 1 when disassembling.

Unscrew the nuts 21 on the rod, remove the pistons 12 as an assembly, the spacer 16 as an assembly with the collar 24 and the sealing rings 17.

Knock pin 26 out of the stem and disconnect stem 23 from pusher 8.

Pneumatic brake booster for Ural car

The parts of the master brake cylinder should be washed in alcohol or brake fluid, the parts of the pneumatic booster should be washed in kerosene or gasoline.

The data for controlling the main dimensions of the parts of the pneumatic booster and the main brake cylinder are given in the table.

Part name

Size, mm



Pneumatic booster cylinders front and rear

Inner diameter



Brake Master Cylinder

Inner diameter



Brake Master Cylinder Piston

Outer diameter



If the seals in the spacer are worn or mechanically damaged, as well as the seals of the piston of the main brake cylinder and the pneumatic booster, replace them. The mirror of the cylinders should not have corrosion and scratches.

There should be no chips or cracks on the main brake cylinder, dents on the pneumatic booster cylinders.

Assemble the pneumatic booster in the reverse order of disassembly, while it is necessary to fulfill a number of the following mandatory requirements:

  • - on the working surface of pneumatic cylinders 9, 19 (see Fig. 1), rod 23, cuff 24 and 13, apply lubricant TsIATIM-201. Felt rings 11 pistons - soak in spindle oil;

Assemble the pneumatic booster pistons in a ring with a diameter of 150+0З mm;

  • - when assembling rod 23 with pistons 12, spacer 16 and pusher 8, it is necessary to maintain the dimensions indicated in fig. 1;
  • - between the support ring 15 of the cuff and the piston 12, install a sealing rubber ring 25;
  • - gasket and bolts 29 for fastening the main brake cylinder to the front cylinder of the pneumatic booster, as well as nuts 21 for fastening the pistons on the rod, install using sealing grease;
  • - install the spacer relative to the front cylinder so that the fittings connecting the outlets are on the same straight line;
  • - set the back cover 20 relative to the front cover 31 so that the surfaces with holes "B" are in the same plane.

The assembled pneumatic booster must be checked for leaks with an air pressure of 4.0—4.5 kgf/cm2.

In this case, the main brake cylinder must create a fluid pressure of 100 - 112 kgf / cm2.

Leaks of liquid and air are not allowed.

Install the boosters on the car, connect the pipelines and bleed the hydraulic system.