Drum Brake System: Service and Repair

Removal

WARNING: Clean brakes with a vacuum dust collector to minimize the hazard of airborne materials.





CAUTION: Make sure parking brake lever is released completely.

1. Release parking brake lever fully, then remove drum.
- If drum is hard to remove, the following procedures should be carried out.





a. Remove adjuster plug. Shorten adjuster as shown to make clearance between brake shoe and drum.





b. Install two bolts as shown. Tighten the two bolts gradually.





2. Pull out retainers and remove the shoe hold-down pins.
3. Pull out brake shoes in the direction of the arrows as illustrated.





4. Using pliers, remove the lower return spring from shoe.





5. Separate shoes, one at a time, from wheel cylinder, and remove them from back plate with the adjuster assembly still on as shown.
- Be careful not to scratch or damage wheel cylinder boot.





6. Disconnect parking brake cable from toggle lever.
- Be careful not to damage parking brake cable when separating it.
7. Remove adjuster return spring and shoe return spring.

Inspection-Wheel Cylinder





- Check wheel cylinder for leakage.
- Check for wear, damage and loose conditions.
Replace if any such condition exists.

Wheel Cylinder Overhaul








- Check all internal parts for wear, rust and damage. Replace if necessary.
- Pay attention so as not to scratch cylinder when installing pistons.

Inspection-Drum





Maximum inner diameter: 230 mm (9.06 inch)
Maximum out-of-round: 0.03 mm (0.0012 inch)

- Contact surface should be fine finished with No. 120 to 150 emery paper.
- Using a drum lathe, lathe brake drum if it shows score, partial wear or stepped wear.
- After brake drum has been completely reconditioned or replaced, check drum and shoes for proper contact pattern.

Inspection-Lining

Measuring Brake Lining:

Check lining thickness.
Standard lining thickness: 4.3 mm (0.169 inch)
Lining wear limit (A): 1.5 mm (0.059 inch)

Installation
- Always perform shoe clearance adjustment.
- Burnish the brake contact surfaces after refinishing or replacing drums or rotors, after replacing pads or linings, or if a soft pedal occurs at very low mileage.





2. Apply brake grease to the contact areas shown.





3. Shorten adjuster by rotating it.
- Pay attention to direction of adjuster.
4. Apply brake grease to adjuster as shown.





5. Install adjuster and adjuster lever; then install upper return spring and adjuster spring.








6. Connect parking brake cable to toggle lever.
- Be careful not to damage brake cable.





7. Install shoes on wheel cylinder one at a time.
- Do not allow the piston to spring away when assembling.
- Be careful not to damage wheel cylinder piston boots.
8. Install lower return spring.





9. Secure shoe installation with shoe hold-down pins and retainers.
10. Check all parts are installed properly.
- Pay attention to direction of adjuster assembly.
11. Install brake drum.
12. When installing new wheel cylinder or overhauling wheel cylinder, bleed air.
13. Adjust parking brake.