Wheel cylinders
Check the cleanliness of the working surfaces of the cylinder, pistons and thrust rings. The surfaces must be completely smooth, without roughness, to prevent fluid leakage and premature wear of the seals and pistons. Eliminate defects on the cylinder mirror by grinding or polishing. However, increasing the internal diameter of the cylinder is not allowed.
Check the condition of the stop screw 3 (fig. 6-20), spring 6, thrust cup 7 and crackers 5. If necessary, replace damaged parts with new ones.
Replace the seals 8 with new ones. Check the condition of the protective caps 10 and replace them if necessary.
Pads
Check the pads carefully for damage or deformation.
Check the elasticity of the upper and lower tension springs; replace them with new ones if necessary.
The springs must not have residual deformations when stretched with a force of 350 N (35 kgf) for the lower springs and 420 N (42 kgf) for the upper springs.
Check the cleanliness of the linings, if dirt or traces of grease are found, thoroughly clean the linings with a metal brush and wash with white spirit, in addition, check for grease leaks inside the drum; fix the faults. Replace the pads with new ones if the thickness of the linings has become less than 1.5-2 mm.
Brake drums
Inspect the brake drums. If there are deep scratches or excessive ovality on the working surface, bore the drums. Then grind them on a machine with fine-grained abrasive bars. This will increase the durability of the linings and improve the uniformity and efficiency of braking.
The maximum allowable increase in the nominal drum diameter (250 mm) after turning and grinding is 1 mm. The limits of this tolerance must be strictly observed, otherwise the strength of the drum is impaired, as well as the braking efficiency due to a decrease in drum rigidity.