Brake drums.
Examine the brake drums. If the working sur-
faces have deep risks or excessive ovality, chisel the drums.
Then grind on a machine tool with abrasive fine stones. This will
help to increase the lining durability, and improve the uniformity
and efficiency of braking.
The maximum allowable increase of drum nominal diameter
(250 mm) after turning and polishing is 1 mm. These dimension
limits should be strictly observed, otherwise, the durability of the
drum, and the efficiency of braking will be decreased due to
reduction of drum rigidity.
Rear brake wheel cylinder -test-bench inspection
Position cylinder 2 (fig. 6-21) on the test bench, attach the
pipeline from the manometers and bleed the system.
Adjust rests1 so that the wheel cylinder pistons are rested
against them.
Check for liquid leak. Connect a low pressure manometer 4.
Slowly rotate flywheel 8 to obtain liquid pressure of 0.05 MPA
(0.5 kgf/cm
2
) as read by the pressure gauge 4.
Ensure that pressure holds steady for 5 minutes. Repeat sim-
ilar test at liquid pressure of 0.1 - 0.2 - 0.3 - 0.4 - 0.5 MPA (1 - 2
- 3 - 4 - 5 kgf/cm
2
).
Reduce pressure and connect a high pressure manometer 5.
Ensure that pressure holds steady for 5 minutes, repeat similar
test at liquid pressure of 5 - 10 - 15 MPA (50 - 100 - 150 kgf/cm
2
).
There should be no pressure decrease due to liquid leak
through sealing elements, pipeline connections, bleeding con-
nectors or through casting pores.
An insignificant reduction of pressure (no more than 0.5 MPA
(5 kgf/cm
2
) during 5 minutes is permissible, especially at high
pressure, due to shrinkage of sealings.
Rear brake pressure regulator
Removal and refitting.
Disconnect arm 12 (fig. 6-22) from
tie-rod 7, and holder 18 from bracket 14 and shackle that is fas-
tening the pipelines going to the pressure regulator.
Disconnect the components of muffler mounting from the
body and move the pipeline with the mufflers aside.
Undo the bolts fastening the regulator on the bracket and the
bracket on the car body, remove the regulator bracket, and then,
having lowered the regulator downward, disconnect the
pipelines.
132
Fig. 6-19. Wheel cylinder:
1 - shoe abutment plate; 2 - cap; 3 - cylinder body; 4 - piston; 5 - seal; 6 - backing cup; 7 - spring; 8 - retainers; 9 - thrust ring; 10 - thrust screw; 11 - bleed screw; A - slot
in thrust ring
Fig. 6-20. Wheel cylinder components:
1 - piston assembly; 2 - cylinder body; 3 - thrust screw; 4 - thrust ring; 5 - retainers; 6 - spring; 7 - backing cup; 8 - seal; 9 - piston; 10 - cap
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