Before performing repair operations, the brake mechanisms should be thoroughly washed with warm water and detergents and dried with compressed air
To disassemble the rear wheel brake mechanism, you must:
- perform operations to remove the brake pads (see "How to replace the rear pads GAZ-2705");
Fig. 1. Removing the thrust ring
- disconnect the pipeline from the wheel cylinder, remove the wheel cylinder and disassemble it.
To do this, you must first remove the rubber protective caps and polyurethane foam rings.
Then turn the pistons 90° with a screwdriver and remove them from the cylinder.
Spring thrust washers should not be removed unnecessarily. If for some reason the ring needs to be removed, then special round-nose pliers are used for this (Fig. 1).
Introducing the round jaws (jaw diameter 4 mm and height 5 mm) of the tool into two special holes on the ring, squeeze the round nose pliers and remove first one and then the second ring from the cylinder.
Remove the wheel cylinder bleed valve.
Wash all parts with warm water and detergents and dry with compressed air, and then inspect the parts of the brake mechanisms.
The brake drum on the working surface should not have deep scratches and burrs.
If necessary, the drum should be bored in assembly with the hub relative to the outer rings of the bearings.
The runout of the working surface of the drum should be no more than 0.2 mm. In order not to reduce the strength of the drum, it is not allowed to bore its inner diameter more than 283.0 + 0.2 mm.
In case of damage or especially deep risks, as well as if it is necessary to bore the working surface of the drum to a diameter of more than 283 mm, it must be replaced with a new one.
Brake pads are glued on.
Before gluing the rim surfaces of the pads and the inner surfaces of the lining should be carefully cleaned and blown with compressed air.
Apply an even layer of adhesive and let it dry for 1 hour at room temperature.
Then, in a special device, press the lining against the blocks with a force of 500-800 kPa (5-8 kgf / cm 2).
Put the device in the oven, where it is kept at a temperature of 175-185 ° C for at least 30 minutes, excluding the time of heating the oven and pads to the specified temperature, then cool the device together with the oven to ambient temperature for 3 hours, at least.
After gluing, the outer surface of the pads is ground so that the radius is 0.1-0.3 mm less than the radius of the drum, which speeds up the running-in of the pads.
Pads with pads that are worn out or oily during operation must be replaced with new ones.
It is allowed to use pads with partially oiled linings for further operation. In this case, the lining must be washed with unleaded gasoline, dried and cleaned with a steel brush or sandpaper.
Do not replace only one of the brake pads or the pads of one brake mechanism.
It is necessary to replace the pads on both brake mechanisms in order to prevent the vehicle from pulling when braking.
It should be checked whether the mounting holes of the shield and wheel cylinders are broken. The shield must not be bent.
Cracks on the shield are not allowed.
Wash the wheel cylinder and its parts in isopropyl alcohol or clean brake fluid.
Clean the mirror of the cylinder with a clean cloth.
The working surface must be completely smooth, without scratches and roughness. Eliminate defects by lapping.
If the wheel cylinder piston is scuffed, corroded that cannot be removed without damaging the base metal, or has one-sided wear, it should be replaced with a new one.
If the sealing rubber rings of the wheel cylinders have lost their original shape or have defects on the working surface, they should also be replaced with new ones.
The protective covers of the wheel cylinders should be changed if there is the slightest damage, as a result of which the tightness is broken.
Ingress of moisture under the protective covers leads to the formation of corrosion on the surface of the cylinder and on the piston, which can cause piston seizure or premature wear of the o-rings.
Assembly of the brakes is done in the reverse order of disassembly.
In this case, it is necessary: - before assembling, wash the parts of the wheel cylinders in a soda solution, blow with compressed air and immerse in fresh brake fluid;
Fig. 3. The position of the thrust rings in the cylinders
- check the location of the slot of the automatic adjustment stop ring, which must be in the vertical plane.
The depth "A" (Fig. 3) of the installation of the thrust ring in the wheel cylinder must correspond to 11 + 0.5 mm;
- make sure that mineral oil, kerosene and grease do not get on the sealing rings during assembly. Rings must not be twisted. After assembling the brake mechanisms of the rear wheels, add brake fluid and bleed the system.