Remove protective caps 2 (figure 6-20), then press out pistons 4 from cylinder body 3 together with the parts of the automatic clearance adjustment device between the brake shoes and the drum.
Figure 6-20. Wheel cylinder:
1 - brake shoe stop;
2 - protective cap;
3 - cylinder body;
4 - piston;
5 - seal;
6 - support cup;
7 - spring;
8 - crackers;
9 - thrust ring;
10 - stop screw;
11 - nipple;
A - slot on the thrust ring.
Install the piston assembly with the automatic device on a special fixture so that the projections of the fixture cover the head of the stop screw 3 (figure 6-21). Using a screwdriver, turn piston 9 and unscrew stop screw 3 from the piston. Remove seal 8 with support cup 7 and crackers 5 from the screw. Disconnect stop ring 4 and stop screw 3.
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.
Assemble the automatic device and the wheel cylinder itself in the reverse order, taking into account the following:
- tighten the piston stop screws with a torque of 4...7 Nm (0.4...0.7 kgf·m);
- slot A (see figure 6-18) on the thrust rings should be directed vertically upwards; deviation from the vertical is allowed no more than 30°. This location of the slot ensures more complete removal of air from the brake mechanism drive during its bleeding;
- to pre-compress the thrust rings, press the pistons into the cylinder body using a special device shaped like a cylinder with a conical inner hole;
- the force required to press the piston into the cylinder must be at least 350 N (35 kgf); if the force is less than 350 N (35 kgf), replace the thrust ring;
- when pressing the piston into the cylinder, it is necessary to maintain dimensions of 4.5 - 4.8 mm and 67 mm (maximum) (see figure 6-18) for free fit of brake drum;
- before installing the parts into the cylinder body, lubricate them generously with brake fluid.
Figure 6-18. Rear wheel brake mechanism:
1 - wheel cylinder;
2 - upper brake shoe tension spring;
3 - pad pad;
4 - brake shield;
5 - inner plate;
6 - rear cable sheath;
7 - lower brake shoe tension spring;
8 - front brake shoe;
9 - Brake pad support plate;
10 - rivets;
11 - oil deflector;
12 - brake shoe guide plates;
13 - rear parking brake cable;
14 - rear cable spring;
15 - rear cable tip;
16 - rear brake shoe;
17 - support stand of the shoe;
18 - manual brake pad drive lever;
19 - rubber cushions;
20 - brake shoe spacer bar;
21 - finger of the manual brake shoe drive lever.
After assembly, check the movement of each piston in the cylinder body. They should move easily within 1.25-1.65 mm. Lastly, install the protective caps 2.
The source of the article is available on the website: chevyman