Check the condition of the stop screw 3 (see fig. 6-21), springs 6, thrust cup 7 and crackers 5. If necessary, replace damaged parts with new ones.
Pic. 6-21. Wheel Cylinder Details:
1 - piston assembly;
2 - cylinder body;
3 - stop screw;
4 - thrust ring;
5 - crackers;
6 - spring;
7 - support cup;
8 - sealant;
9 - piston;
10 - protective cap.
Replace 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 coupling springs; replace them if necessary.
Pads. Check the cleanliness of the linings, if dirt or traces of grease are found, carefully clean the linings with a wire brush and rinse with mineral spirits, in addition, check if there is any leakage of grease inside the drum; troubleshoot.
Carefully inspect the pads, check for any deformation or damage on the pads - chips, cracks, delamination from the frame.
Measure the remaining thickness of the brake lining with a vernier caliper (pic. 6-22).
Pic. 6-22. Measuring the thickness of the brake pads
Rear brake linings wear unevenly, so measurements must be taken at several places with the smallest thickness.
Replace pads with new ones if pad 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 carried out through the inspection hole in the brake shield by 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, then bore the drums. Then grind on the machine with abrasive fine-grained 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 an inside gauge fitted with the appropriate extension rods. Brake drum wear or roundness should be measured by 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, regrind it. The maximum value of the difference when measuring diameters should not exceed 0.1 mm.
The largest allowable increase in the nominal diameter of the drum (250 mm) after turning and grinding 1 mm. The limits of this tolerance must be strictly observed, otherwise the strength of the drum is violated, as well as the effectiveness of braking due to a decrease in the rigidity of the drum.
The limiting diameter as a result of wear of the inner diameter of the drum should not exceed 251.6 mm.