Check the condition of the stop screw 3 (see figure 6-21), springs 6, thrust cup 7 and crackers 5. If necessary, replace damaged parts with new ones.
Figure 6-21. Wheel cylinder parts:
1 - piston assembly;
2 - cylinder body;
3 - stop screw;
4 - thrust ring;
5 - crackers;
6 - spring;
7 - support cup;
8 - seal;
9 - piston;
10 - protective cap.
Replace the seals 8 with new ones. Check the condition of the protective caps 10 and replace them if necessary.
Check the elasticity of the upper and lower tension springs; replace them with new ones if necessary.
Pads. 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; please fix the problems.
Carefully inspect the pads, check for any deformations or damage on the pads - chips, cracks, delamination from the frame.
Measure the remaining brake lining thickness using a caliper (figure 6-22).
Figure 6-22. Measuring brake pad thickness
The rear brake linings wear unevenly, so measurements must be taken in several places that have the smallest thickness.
Replace the pads with new ones if the lining thickness is less than 2 mm.
When operating a car with a mileage of more than 30,000 km, it is necessary to check the degree of wear of the brake pads at each maintenance. A preliminary assessment of wear can be made through the inspection hole in the brake shield, removing the rubber plug. For a more accurate assessment, it is necessary to dismantle the brake drum.
Brake drums. Inspect the brake drums. If there are deep scratches or deviations from roundness 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 degree of wear or out-of-roundness of the brake drum can be accurately measured with a bore gauge fitted with appropriate extension rods. The wear or out-of-roundness of the brake drum should be measured on the inside diameter of the machined surface in sectors at 90° intervals around the circumference of the drum.
If the brake drum exceeds the specified roundness limit, grind it again. The maximum difference in diameter measurements should not exceed 0.1 mm.
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.
The maximum diameter due to wear of the inner diameter of the drum should not exceed 251.6 mm.
The source of the article is available on the website chevyman.ru