Warning: Before starting work, please read the warning at the beginning Section 2 about the dangers of brake fluid and a warning at the beginning Section 4 about the dangers of asbestos-containing dust.
Removal
1. Remove the rear brake pads as described in previous Section.
2. Using the patented clamp, clamp the flexible brake hose in front of the rear axle. This will reduce the loss of brake fluid during subsequent work.
3. Wipe away all traces of dirt from around the brake pipe nipple at the rear of the brake cylinder, then use a wrench, if possible, to loosen the union nut. Plug or tape the disconnected fitting to prevent dirt from getting inside (see Figure 9.3).
Figure 9.3. Brake pipe connection and nipple (indicated by the arrow) on the back of the brake cylinder.
4. Unscrew the nipple from the rear of the brake cylinder
5. Depending on the type of cylinder, either remove the retaining washer from the rear of the brake cylinder by prying it with a screwdriver, or unscrew the two retaining bolts. Remove the cylinder from the protective cover.
Disassembly
6. After cleaning the outside of the cylinder, remove the protective caps from both ends of the cylinder.
7. The pistons with seals will probably fall out on their own, but if this does not happen, force them out by pumping air through the fitting with a foot pump. Remove the spring installed between the pistons.
8. Paying attention to their installation direction, remove the seals from the pistons.
9. Clean the pistons and cylinder by rinsing them with fresh brake fluid or methyl alcohol (under no circumstances use gasoline, paraffin or other liquids with a mineral base) Inspect the pistons and their cylinder bores for any signs of rust, nicks, or wear from metal-to-metal friction, which, if clearly visible, indicate the brake cylinder component requires replacement (see figure 9.9).
Figure 9.9. Rear brake cylinder: A - Protective caps, B - Pistons, C - Piston seals, D - Spring, E - Brake cylinder housing.
10. Once completed, test drive the vehicle on the road to check the operation of the brakes. If new brake pads have been installed, brake performance may be slightly reduced until the pads have been bedded in.
11. Begin assembly by thoroughly dipping the piston in clean brake fluid, then install the new seal in the installation position so that the convex contact edges of the seal face away from the piston.
11. Insert the piston into the cylinder from the opposite side of the cylinder body and push it into the sleeve.
12. Insert the spring into the cylinder, then install the second new seal into the second piston (as described for the first) and insert the second piston into the brake cylinder. When inserting the piston into the cylinder, be careful not to damage the seal contact lip. A slight excess of grease and rotating the seal will help. When installing the piston and seal, avoid using any tools, using only your hands.
13. Install new protective caps on the end of each piston and the cylinder body.
Installation
14. Clean the brake cylinder location on the protective cover.
15. Install the brake cylinder in the reverse order of removal, paying attention to the following additional points:
- a) If the brake cylinders are secured with retaining washers, replace them with new ones each time you remove them;
- b) When installing the locking washers on the brake cylinder, a special tool will be useful (see Figure 9.15). If the tool is not easy to get, it is enough to simply make one from a short piece of flexible tubing, a threaded rod and a nut with a washer;
- c) Make sure that the guide pin of the brake cylinder is aligned with the hole in the protective cover;
- d) After installing the brake shoes, brake drum and hub, bleed the brake system as described in Section 2, then press the brake pedal several times to activate the automatic adjustment mechanism;
- d) Adjust the handbrake, if necessary, as described in Section 14.
Figure 9.15. Device for securing the locking washer to the brake cylinder.