Rear wheel cylinder - removal, overhaul and refitting
Removal
1 Remove the brake drum.
2 Disconnect the fluid pipeline from the wheel cylinder and cap the end of the pipe to prevent loss of fluid. A bleed screw rubber dust cap is useful for this.
3 Unscrew the two bolts which hold the wheel cylinder to the brake backplate.
Rear wheel cylinder retaining bolts (arrowed)
4 To avoid removing the brake shoes when withdrawing the wheel cylinder, prise the shoes away from the cylinder (at the top) so that the automatic adjuster holds them clear of it. The cylinder can then be withdrawn.
Rear wheel cylinder removal (brake shoes expanded in direction of arrows)
Overhaul
5 Clean away external dirt and then pull off the dust-excluding covers from the cylinder unit.
Wheel cylinder components
A Spring
B Bleed nipple
C Retaining bolts
D Lockwasher
E Piston housing
F Piston seal
G Piston
H Dust cover
J Gaiter springs
6 The pistons will probably shake out. If they do not, apply air pressure (from a tyre pump) at the fluid inlet hole to eject them.
7 Examine the surfaces of the pistons and the cylinder bores for scoring or metal-to-metal rubbing areas. If evident, renew the complete cylinder assembly.
8 Where the components are in good condition, discard the rubber seals and dust excluders and obtain a repair kit.
9 Any cleaning should be done using hydraulic fluid or methylated spirit - nothing else.
10 Reassemble by dipping the first piston in clean hydraulic fluid and inserting it into the cylinder. Fit a dust excluder to it.
11 From the opposite end of the cylinder body, insert a new seal, spring, a second new seal, the second piston and the remaining dust excluder. Use only the fingers to manipulate the seals into position and make quite sure that the lips of the seals are the correct way round.
Refitting
12 Refit the cylinder to the backplate and secure with the two bolts and lockwashers.
13 Remove the plug and reconnect the hydraulic fluid pipe, taking care not to crossthread the connection. Do not overtighten the union, but tighten it sufficiently to seal it. For the torque setting refer to Specifications.
14 Relocate the brake shoes against the cylinder pistons by releasing the automatic adjuster.
15 Refit the brake drum and hub unit. Bleed the hydraulic circuit on completion.