Piping and connections
To prevent failure of the brake system, carefully check the connection of all pipelines.
When checking, make sure that:
- metal pipelines had no cracks, dents and were located away from sharp edges that could damage them;
- flexible hoses have not come into contact with mineral oils or rubber-dissolving lubricants. By strongly pressing the brake pedal, they check to see if swelling appears on the hoses, indicating malfunctions;
- All piping clamps are well tightened. Loose fastening leads to vibration causing breakage;
- there was no fluid leakage from the fittings. If necessary, tighten the nuts to failure without exposing the pipelines to deformation.
Parts are replaced with new ones at the slightest doubt about their suitability. Flexible hoses, regardless of their condition, are replaced with new ones after 100 thousand kilometers or after 5 years of vehicle operation.
Wheel cylinders
To check the wheel cylinders are disassembled: remove the protective caps 5 (see fig. 147) and pistons 4, take out the seals 3, the support cups 2 and the spring 6, then unscrew the air outlet fitting 1.
Check the working surfaces of the cylinder and pistons. Surfaces must be perfectly smooth, without visible scratches and roughness. Minor damage to the cylinder mirror is repaired by lapping.
Check the elasticity of the spring, the length of which in the free state should be 34 mm, under load (3,5±0,2) kgf - 17.8 mm.
Replace the seals with new ones, also check that the protective caps of the cylinder are not damaged and, if necessary, replace them with new ones.
Before assembly, liberally lubricate all parts with brake fluid. In the reverse order of disassembly, the parts are installed in the cylinder body without effort, so as not to damage the rubbing surfaces. Install protective caps. Using both hands, check the movement of the pistons, which should be smooth, without jamming.
Pads
Carefully check for damage to the pads (deformations). Check the elasticity of the coupling springs, both upper and lower. The springs should not have residual deformations when stretched with a force of 35 kgf of the lower springs and 42 kgf of the upper ones. If necessary, replace them with new ones.
Look at the pads. If dirt or traces of grease are found, the linings are thoroughly cleaned with a wire brush and washed with white spirit. In addition, check if there is any leakage of grease or oil inside the drum. Faults are eliminated. The pads are replaced with new ones if the thickness of the pads has become less than 1.5-2 mm.
Brake drums
Inspect brake drums. If there are deep risks on the working surface, then the drums are bored on the machine, and then with grinding bars (grain size 10-16) remove irregularities from the working surface. This increases the durability of the linings and improves braking uniformity and efficiency.
The most permissible increase in the nominal diameter of the drum (250 mm) after boring 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.
Drum wear is allowed up to a diameter of not more than 251.6 mm.