Caliper - removal, overhaul and refitting

Braking system / Caliper - removal, overhaul and refitting

Note: Purchase a repair kit in advance of overhaul.

1 Jack up the front roadwheel and remove it.

2 Brush away all dirt from the caliper assembly and the flexible pipe, particularly the fixing bracket and union at the car end of the flexible pipe.

3 Have ready a container suitable to catch the brake fluid, and sheets of clean newspaper on which to put parts.

4 Take out the spring clips and locking blocks, and take the caliper off the support bracket.

5 Disconnect the hydraulic flexible pipe at the under wing support bracket and cap both pipe ends. It may help to prevent loss of fluid if the vent in the reservoir cap is sealed with adhesive tape, to create a vacuum.

6 Remove the caliper to the bench or other work surface, and clean it thoroughly with hydraulic fluid or methylated spirit.

7 Depress the piston until the dust excluding boot can be removed.

8 Now apply air pressure to the flexible hose and eject the piston. Quite a low pressure is required for this, such as can be generated with a hand or foot operated pump.

9 Pick out the piston seal from its groove in the cylinder. Use a sharp probe, but take care to avoid scratching the cylinder bore.

10 Examine the surface of the piston and cylinder bore. If either is corroded, scored or shows metal-to-metal rubbed areas, the complete assembly should be renewed.

11 If the components are in good condition, discard the oil seals, clean the piston and cylinder and fit the new seal for the piston.

This is included in the repair kit. Use the fingers only to manipulate it into its groove.

12 Lubricate the piston with clean hydraulic fluid and insert it partially into the cylinder.

13 Fit the new dust excluding boot to its projecting end, push the piston fully into the cylinder and engage the dust excluder with the rim of the cylinder.

14 Refit the caliper, reconnect the flexible hose, then bleed the front hydraulic circuit (refer to Section 12).

Fig. 8.2 Exploded view of caliper (Sec 5)

Fig. 8.3 Sectional view of caliper (Sec 5)

1 Pads
2 Dust excluder
3 Piston seal
4 Piston
5 Cylinder body