Opel Corsa B 1993–2000 Service and Repair Manual: Rear wheel cylinder - removal, overhaul and refitting

Note: Before starting work, refer to the note at the beginning of Section 2 concerning the dangers of hydraulic fluid and to the warning at the beginning of Section 6 concerning the dangers of asbestos dust.

Removal

1. Remove the brake drum.

2. Using pliers, carefully unhook the upper brake shoe return spring and remove it from both brake shoes. Pull the upper ends of the shoes away from the wheel cylinder to disengage them from the pistons.

3. Minimise fluid loss by either removing the master cylinder reservoir cap and then tightening it down onto a piece of polythene to obtain an airtight seal, or by using a brake hose clamp, a G-clamp or a similar tool to clamp the flexible hose at the nearest convenient point to the wheel cylinder.

4. Wipe away all traces of dirt around the brake pipe union at the rear of the wheel cylinder and unscrew the union nut. Carefully ease the pipe out of the wheel cylinder and plug or tape over its end to prevent dirt entry.

Wipe off any spilt fluid immediately.

5. Unscrew the two wheel cylinder retaining bolts from the rear of the backplate and remove the cylinder taking great care not to allow surplus hydraulic fluid to contaminate the brake shoe linings.

Overhaul

6. Brush the dirt and dust from the wheel cylinder, taking care not to inhale it, and pull off the rubber dust excluders from the cylinder body (see illustration).

Exploded view of a rear wheel cylinder

1. Dust cap
2. Bleed screw
3. Cylinder body
4. Dust excluder
5. Piston
6. Seal
7. Spring

7. The pistons will normally be ejected by pressure of the coil spring but if they are not, tap the end of the cylinder on a piece of hardwood or apply low air pressure from a tyre foot pump at the pipeline connection.

8. Inspect the surfaces of the piston and the cylinder bore for rust, scoring or metal-tometal rubbed areas. If these are evident, renew the wheel cylinder complete.

9. If these components are in good order, discard the seals and dust excluders and obtain a repair kit which will contain all the renewable items.

10. Fit the piston seals (using the fingers only to manipulate them into position) so that the spring is between them. Dip the pistons in clean hydraulic fluid and insert them into the cylinder.

11. Fit the dust excluders.

Refitting

12. Ensure that the backplate and wheel cylinder mating surfaces are clean then spread the brake shoes and manoeuvre the wheel cylinder into position.

13. Engage the brake pipe and screw in the union nut two or three turns to ensure that the thread has started.

14. Insert the two wheel cylinder retaining bolts and tighten them to the specified torque setting. Now tighten the brake pipe union nut to the specified torque.

15. Remove the clamp from the flexible brake hose or the polythene from the master cylinder reservoir (as applicable).

16. Ensure that the brake shoes are correctly located in the cylinder pistons then carefully refit the brake shoe upper return spring, using a screwdriver to stretch the spring into position.

17. Refit the brake drum.

18. Bleed the brake hydraulic system. Providing suitable precautions were taken to minimise loss of fluid, it should only be necessary to bleed the relevant rear brake.