Inspection and repair of the brake drum. Clean the brake drum from dirt, remove rust and clean the nicks
Replace the brake drum if it is cracked, deformed, or loose on the hub.
Before replacing the brake drum, make sure there is no vacuum in the system. Do not press the brake pedal after removing the brake drum.
Small scuffs, scratches on the surface of the brake drum can be removed with fine-grained emery cloth, and then thoroughly clean the surface of the drum.
If the drum, seated on the hub, has an ovality and runout of more than 0.25 mm, as well as deep scratches and scuffs, then, based on the outer rings of the hub bearings, bore the drum by the amount necessary to obtain a smooth working surface and runout of no more than 0 .12 mm.
Do not remove a thicker layer from the surface of the drum than necessary.
The diameter of the restored drum should increase by no more than 1.5 mm, i.e. it should be no more than 381.75 mm for the brakes of all wheels of the GAZ-66 car, the rear wheels of the GAZ-53A car and 357.25 mm for brakes of the front wheels of the GAZ-53A car.
If the diameter of the drum has increased by less than 0.8 mm, then use standard brake pad friction linings, and if more than 0.8 mm, then use oversized friction linings or install metal spacers between the linings and rims of the pads.
Remove the wheel brake cylinder in the following order.
Remove the vacuum from the brake booster system.
Remove the wheel and drum. Remove the shoe compressing springs.
Disconnect the coupling and pipe or hose from the brake cylinder.
When removing the brake cylinder of the front wheel of the GAZ-66 car, unscrew the nut with the spring washer of the pad support pin and remove the pin with the brass eccentric and washer.
Remove the pad and cylinder from the brake disc.
When removing the brake cylinder of the rear wheel of the GAZ-66 car and the brake cylinders of all wheels of the GAZ-53A car, unscrew the mounting bolts of each brake cylinder and remove the spring washers and the screen of the car (GAZ-53A).
Disassemble the wheel brake cylinder in the following order.
Remove the rubber caps from the ends of the brake cylinder, remove the pistons, cuffs, spacer cups with springs. Remove the rubber caps from the pistons.
Unscrew the bypass valve from the cylinder.
Wash the brake cylinder parts in pure alcohol.
Inspection and repair of parts of the wheel brake cylinder. The wheel brake cylinder is washed in alcohol, and the mirror is wiped with a clean cloth.
If there is corrosion, scratches, scuffs, it is honed to a value of no more than 0.125 mm, i.e. no more than Ø 35.152 mm.
In this case, you need to put new cuffs.
If after honing the defect has not been eliminated or there is a leak of liquid from the assembled cylinder, then bore the cylinder and then honing it to one of the repair sizes.
At the same time, pistons, cuffs and spacer cups of the appropriate repair size are installed.
The piston of the wheel brake cylinder must be free of corrosion and scuffing. If present, the piston should be replaced.
If there is rocking of the thrust rod, then also replace the piston.
The cuff of the cylinder should be elastic, with a sharp working edge and without flaws.
The protective covershould not be cracked and must be elastic.
Springshould not be corroded. Under a load of 0.95+0.1kgthe spring must be compressed to a height of 25mm.
The spacer cup of the cuff should not have dents or nicks; when installed in the cylinder, it should evenly adjoin the sealing edge of the cuff and not touch its bottom.
The relief valveshould have a good sealing cone surface. The longitudinal and transverse holes must be clean.
Assembling and testing the wheel cylinder
Before assembling, wash all parts of the wheel cylinders in pure alcohol and blow with compressed air. Lubricate the cuffs and the mirror of the cylinder with brake fluid.
Assemble the cylinder in the reverse order of disassembly. To test the cylinder, immerse it in alcohol and apply air at a pressure of 5-6 kg/cm2 into the threaded hole.
When the bypass valve is turned off, air must be expelled vigorously from the opening. When the valve is closed, there should be no air outlet.
Put the rubber cap on the bypass valve.
Installing wheel brake cylinders
The wheel brake cylinders are installed in the reverse order of their removal.
When installing a coupling with new copper do not tighten the bolt to failure.
Finally tighten the bolt after connecting the pipeline to the coupling. After installing all the parts in place, adjust the brakes and bleed the system.
When replacing the brake pads, do not press the brake pedal, as brake fluid may leak out. Brake pads must be removed in the following sequence.
Loosen the wheel nuts first. Hang the wheel up so it can spin freely. Remove the wheel and drum.
Secure the pistons of the wheel cylinders from falling out. Remove the shoe return spring(s).
Remove the nuts of the pad support pins. While holding the support pins from turning with keys, remove the fingers, eccentrics, washers, support pin plate.
Checking and repairing pads
When the overlays are tarred, clean the surface with sandpaper, when oiling, rinse with gasoline.
If uneven braking was noticed during operation, it is necessary to check the curvature of the lining according to the template with a radius of 189.80 mm and the front lining (brake of the GAZ-53A car with a radius) of 177.55 mm.
A gap of no more than 0.30 mm is allowed.
Out-of-circle and uneven wear can be corrected by grinding if the rivets are sunk deep enough.
If the depth of rivets is less than 0.5 mm, replace the lining.
Do not replace just one of the brake pads or linings on one side of the vehicle.
If it is necessary to replace the pads on one brake, simultaneously replace them on the brake of the other side to prevent the car from skidding when braking.
When changing overlays, you must:
- - drill or cut the rivets of the overlays;
- - clean up all burrs and irregularities of the block;
- - check if the block is deformed, if the fastening of the rim to the edge is not weakened;
- - check the state of the hole for the support pin;
- - check the curvature of the shoe rim with a template. With a template radius of 182 mm for all pads and 172 mm for the GAZ-53A front brake pads, a 0.3 mm thick probe should not pass between the template and the rim of the pad;
- - install a new friction lining on the block and, starting from the middle holes, rivet it with new rivets to the rim;
- - check the gap between the lining and the rim of the shoe.
The pad should fit snugly against the rim. The 0.25 mm probe should not pass between them to a depth of more than 20 mm.
In width, the lining should not protrude beyond the rim of the shoe. At the ends of the lining there should be bevels 8-14 mm long;
- - grind the pads so that their diameter is 0.2 - 0.4 mm less than the diameter of the drum. This will speed up the adjustment of the gaps, ensuring that the linings fit evenly on the drum;
- - install the pads in the reverse order of their removal, adjust the brakes and bleed the brake system. When installing the pads, make sure that the support pins are installed with the marks inside.
For brake adjustment, see the article Design, malfunctions and maintenance of brakes GAZ-66, GAZ-53
After the break-in of the brakes, repeat the adjustment of the gap between the linings and the brake drums.