2. Unscrew and remove the caliper fluid coupling bolt. Plug the coupling with two suitable rings or allow the liquid to drain into a container.
3. For older models, unscrew the two caliper mounting bolts and remove the caliper.
4. On latest models, remove the caliper from the mounting plate by pressing the caliper inward from the front (towards the wheel hub) and at the same time moving the caliper towards the center of the machine.
5. Clean any external dirt from the caliper assembly without inhaling the powder. Secure the caliper in a vice. Use soft attachments on the vise and be careful not to damage or distort the caliper.
6. On older models, separate the caliper body from its bracket by removing it from its keyways (Pic. 9.4).
Pic. 9.4 — Disconnecting the ATE type caliper body from the bracket (old type)
7. Using a screwdriver, remove the retaining ring from the boot (Pic. 9.5).
Pic. 9.5 — Removing the boot retaining ring
8. Remove the boot (Pic. 9.6).
Pic. 9.6 — Removing the caliper boot
9. Place a thin piece of wood or cardboard on the end of the piston and apply compressed air to the tube connection on the caliper body. Removing the piston will require gentle air pressure, such as from a foot-operated tire pump.
10. After removing the piston, pull the seal out of its groove in the cylinder using a plastic or wooden tool.
11. Inspect the piston and cylinder barrel surfaces for scratches or signs of metal-on-metal friction. If the damage is beyond doubt, replace the caliper completely.
12. If these components are in good condition, discard the rubber seal and boot and purchase a repair kit that contains all the necessary replacement parts.
13. For the latest type of caliper, the rubber guides can be replaced if necessary. Remove the nylon compression cuff from each rubber guide, and then carefully squeeze the collar of the cuff and press down on it to remove it from the inside (photo).
Photo 4.13A Remove the nylon compression cuff...
Photo 4.13B... and remove the rubber bushing from the caliper (last type).
14. Clean the piston and cylinder barrel with hydraulic fluid or methyl alcohol - and nothing else.
15. Begin assembly by installing the oil seal into the cylinder groove (Pic. 9.7).
Pic. 9.7 — Boot engagement in the piston groove
16. Position the boot in its groove in the piston. Dip the piston in clean brake fluid or lubricate its outer surface with rubber grease, and insert it into the cylinder at a right angle. Make sure that the piston is positioned as shown in Fig. 9.8.
Pic. 9.8 — Caliper piston installation diagram
17. When the piston is partially pressed, connect the boot to the cylinder rim and install the retaining ring.
18. Press the piston so that it goes completely into the cylinder barrel.
19. If you are dealing with the latter type of caliper, then install the rubber guide sleeve and insert the compression collar. Be careful not to damage the guide sleeve and collar during installation and ensure that the rubber guide sleeve collar is fully engaged (photo).
Photo 4.19 Guide bushing, reinstalled on the caliper (last type).
20. On older models, secure the caliper bracket in a vice and install the guide springs (Pic. 9.9). Install the caliper body into the keyways of the caliper so that the body and the caliper are located close to each other (Pic. 9.10).
Pic. 9.9 — Installing caliper bracket guide springs
Pic. 9.10 - Caliper body and bracket connected at the same level - location indicated by arrow
21. Install the caliper onto the hub holder. On older models, clean the threads of the mounting bolts and lubricate them with a thread-locking compound. Install the bolts, tighten them to the specified torque value and then install the disc pads as indicated in Section 3. On later models, install the caliper onto the guide pins and push it into place (photo), and then install the disc pads.
Photo 4.21 New type caliper assembly (type ATE).
22. Connect the fluid hose using new seals in the coupling.
23. Bleed the system as indicated in Section 20.
24. Install the wheel, paying attention to the alignment marks, and lower the machine to the ground. Press the brake pedal several times to move the pads to the disc, and then add fluid to the master cylinder if necessary.
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