Rear wheel cylinder - removal, overhaul and refitting

Braking system / Rear wheel cylinder - removal, overhaul and refitting

Note: Purchase a repair kit in advance of overhaul.

1 If fluid seepage is observed from the ends of the rear wheel cylinder when the brake drum has been removed, the seals are leaking and immediate action must be taken.

2 Although the cylinder can be dismantled without taking it from the backplate, this is not recommended due to the possibility of under wing dirt and mud dropping onto the components as work proceeds.

3 Remove the brake shoes, as described in Section 4.

4 Disconnect the hydraulic line from the wheel cylinder and cap the open end of the pipe. lt may help to reduce the loss of fluid if the vent hole in the reservoir cap is taped over to create a vacuum.

5 Unscrew and remove the setscrews which hold the cylinder to the backplate and withdraw the cylinder. Prise off the rubber dust excluding boots.

6 Apply gentle air pressure from a hand or foot operated pump to eject the pistons and spring. Alternatively, tap the end of the cylinder on a piece of hardwood and the pistons should move out.

7 Inspect the piston and cylinder bore surfaces for scoring, corrosion or evidence of metal-to-metal rubbing areas. lf these are found, discard the assembly and purchase a new one.

8 If the components are in good condition, note which way round the lips are fitted, then discard the seals and boots and wash the pistons and cylinder bore in clean hydraulic fluid or methylated spirit.

9 Manipulate the new seals into position, using the fingers only for this job.

10 Dip the pistons in clean hydraulic fluid and insert them with the coil spring and washers into the cylinder.

11 Fit the new dust excluding boots.

12 Refit the wheel cylinder to the backplate, reconnect the hydraulic pipe, then refit the shoes, the drum and the roadwheel.

13 Bleed the rear hydraulic circuit as described in Section 12.

Fig. 8.4 Exploded view of a rear wheel cylinder (Sec 7)