Auxiliary brake consists of a drive and two actuators installed in the socket of the exhaust pipes of the muffler of the exhaust system

Auxiliary brake mechanism (Fig. 2) includes housing 3, damper 11, shaft 13 and lever 4.

When the brake is not applied, the damper of the mechanism is located along the exhaust gas flow and the axis of the exhaust pipes.

Auxiliary brake (mountain brake) of a Ural vehicle

The drive for controlling the brake mechanisms is pneumatic, it consists of a crane (Fig. 3), three pneumatic cylinders (pneumatic cylinders) and pipelines connecting them.

When the tap button is pressed, compressed air is supplied through pipelines to two pneumatic cylinders (cylinder diameter 35 mm and piston stroke 65 mm - Fig. 4), the pistons of which set the dampers of the mechanisms perpendicular to the exhaust gas flow.

At the same time, compressed air is supplied to a 30x25 pneumatic cylinder (Fig. 5) mounted on the cover of the high-pressure fuel pump, which turns off the fuel supply.

Ural auxiliary brake mechanism

Auxiliary brake mechanisms 23 (fig. 6) are bolted 2 to the flanges in the connector of the exhaust pipes 3 and 22 of the muffler of the exhaust system.

Brackets 6 for installing pneumatic cylinders 7 are attached to the flanges with the same bolts.

The auxiliary brake control valve is mounted on the front panel of the cab, and its button is located to the left of the clutch pedal.

Ural auxiliary brake system crane

Auxiliary brake units are removed and partially or completely disassembled if malfunctions are detected in them, for example, jamming of the damper shaft in the housing bushings, wear of pneumatic cylinder parts, loosening of the bolts for fastening the mechanisms to the front pipes, etc.

Removing and disassembling the auxiliary brake

When removing, unscrew the nut 18 of the ball pin 19 and disconnect the tip 15 from the lever 5.

Unpin and unscrew the nut 8 of the pin 11, remove the washer and the pneumatic cylinder 7 as an assembly. Unscrew locknuts and nuts of four bolts 2, remove them, remove bracket 6, gaskets 1 and mechanism 23 as an assembly.

To remove the pneumatic cylinder for shutting off the fuel supply, unpin the pins connecting the cylinder to the bracket and the earring on the cylinder rod with the lever of the high pressure fuel pump, remove the cylinder assembly.

Auxiliary brake pneumatic cylinder 35x65

When removing the valve, unscrew the nuts and disconnect the pipelines from it.

Unscrew the nut securing the crane to the cab floor panel and remove it. Parts of the auxiliary brake, being in the exhaust gas environment, are partially corroded, and the gaps between them are clogged with soot particles; therefore, to facilitate disassembly, the auxiliary brake should be kept for a day in kerosene or diesel fuel.

When disassembling the mechanism, cut the head of the rivet 2 (see Fig. 1) with a file and use a drift with a diameter of 4 mm to remove it from the shaft and damper.

Fix the auxiliary brake mechanism to the lever 4 in a vise and, turning the housing 3, remove it from the shaft 13.

Remove damper 11 from the housing.

Remove cover 9 from the body and remove spring 8, washer 7 and retaining ring 6 from it. Unscrew nut 10 of coupling bolt 5 and remove lever 4 and key 15 from shaft 13.

Using a drift with a diameter of 3.5 mm, knock out the pins 1 and 12 from the body and remove the bushings 14.

The bushing can be hydraulically removed from the housing blind hole (fig. 164) using grease.

The damper axle can be used as a rod.

Pneumatic fuel cutoff cylinder 30x25

When disassembling the pneumatic cylinder 35 x 65 of the mechanism drive, it must be fixed in a vise behind the cover 5 (Fig. 161) and unscrew the body 2, remove the sealing ring 3.

Pull piston head 6 out of the cylinder by 10—15 mm and fix it in loosen locknut 14 (see Fig. 6).

Unscrew tip 15 and locknut.

Remove piston 6 (see Fig. 4) complete with rod 1 and springs 8 and 10 from the cylinder.

Remove limiter 9 from stem 1, and cuff 7 from piston. If necessary, disassemble tip.

Before disassembling the 30 x 25 fuel shutoff cylinder,unscrew the nut and disconnect the stop earring from the stem.

Then, clamp the lower part of cylinder 8 (see Fig. 5) in a vice, unscrew cover 2 and remove piston 5 complete with rod 9 and spring 6.

Remove cuff 4 from the piston, and limiter 7 from the rod.

Removing and disassembling the secondary brake

When disassembling the crane (see Fig. 3), secure its lower part in a vise.

Disconnect the lower part of the boot 7 from the sleeve 6.

Remove thrust ring 11 into the gap.

Pull the button 8 and remove the pusher assembly 9 from the body with the cover 7, the sleeve 6, the sealing rings 5, 10 and 14 and the plate 4 of the spring.

Remove spring 13 from the housing.

Move the crane in the vise so that you have access to the bottom of the crane.

Remove thrust ring 1, remove valve guide 17 and O-ring 18 from the body.

Remove inlet valve 15 with stem 16 and valve spring from guide 17.

Remove sealing rings 10,- 14, plate 4, thrust ring 12 and sleeve 6 from pusher 9.

Pneumatic cylinders, mechanisms and crane parts must be washed in gasoline, then dried and carefully inspected.

The hydraulic method of pressing the bushing out of the blind hole

The gaskets between the flanges of the exhaust pipes and the auxiliary brake mechanisms must not have ruptures, delaminations or other damage.

Ruptures, deep marks, hardening and permanent deformation, as well as other damage to rubber parts are not allowed.

Data for monitoring the details of the auxiliary brake mechanism and pneumatic cylinders are given in Table 1.

Part names

(dimension parameter)

Size, mm




Inner diameter



Damper shaft

Outer diameter



Ball pin

Diameter of a spherical surface



Auxiliary Brake Rod End

Ball pin hole diameter



Assemble the auxiliary brake units and install them on the vehicle in the reverse order of disassembly and removal from the vehicle.

The following requirements must be met:

  • - the damper shaft in the bushings must rotate freely without jamming. Lubrication of the shaft and bushings is strictly prohibited;
  • - tip 15 (see Fig. 6) and ball pin 19 lubricate with a thin layer of graphite grease;
  • - lubricate with a thin layer of TsIATIM-221 lubricant: at the auxiliary brake control valve, pusher 9 (see Fig. 3) complete with sealing rings, bushing 6 and housing 2 at the point of contact with the rod; for pneumatic cylinders, a piston assembly with a sealing ring, a rod and a cylinder.

After assembly, check the pneumatic cylinders for tightness under an air pressure of 5.3 kgf / cm2.

Find air leaks with a soapy emulsion, which should be removed after checking.

When checking, it is also necessary to measure the stroke of the rods, which for pneumatic cylinders 35 x 65 should be 65 mm, and for pneumatic cylindersindra 30 x 25-25 mm.

The rods under the action of the springs should return to their original position without jamming.

When installing the auxiliary brake mechanism on the car, it is necessary to adjust the screwing length of the rod L (see Fig. 6) so that when the pneumatic cylinder piston is in its uppermost position, the key 4 is located along the axis of the receiving pipes. In this case, the damper of the mechanism will be fully open.

It is also necessary to check the tightness of the bolts securing the exhaust pipes of the exhaust system, and, if necessary, tighten the bolts securing the exhaust pipes to the exhaust gas pipelines of the engine.