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9 Master cylinder - removal,
overhaul and refitting
4
Note: Purchase a repair kit in advance of
overhaul.
1 The master cylinder is mounted on the front
face of the brake vacuum servo unit (55 and
70 models) or directly to the bulkhead (45
models).
2 Cover the front wings with polythene
sheeting or similar material, in case hydraulic
fluid spills onto the paintwork of the car during
removal of the cylinder.
3 Detach the leads from the terminals on the
reservoir cap, then unscrew and remove the
cap and float.
4 Unscrew the pipe unions and prise the
pipes carefully away from the master cylinder.
Cap the open ends of the pipes and catch any
fluid leaking from the master cylinder in a
suitable container.
5 Unscrew the mounting nuts and withdraw
the master cylinder from the bulkhead or from
the servo unit.
6 Clean away all external dirt and tip out the
fluid from the reservoir and cylinder body.
7 The fluid reservoirs need not be removed
from the master cylinder but if they are, renew
the rubber sealing collars when refitting.
8 Grip the master cylinder in a vice, then
unscrew and remove the end plug. Catch the
coil spring.
9 Using a thin rod, apply pressure to the end
of the primary piston then unscrew and
remove the two stop bolts and sealing
washers.
10 The internal piston assemblies with seals
and springs can now be pushed out of the
cylinder body. Keep all the components in
Braking system 8•5
Fig. 8.5 Sectional view of master cylinder (Sec 9)
1 Cylinder body
2 Spring and cup
3 Inlet from reservoir
4 Secondary piston
5 Seal
6 Fluid outlet to front brakes
7 Spring and cup
8 Inlet from reservoir
9 Primary piston
10 Seal
12 Stop bolts
13 Spacer
14 Springs
15 Seal
16 End plug and fluid outlet to
rear brakes
Fig. 8.6 Exploded view of master cylinder (Sec 9)
1 Cylinder body 2 Secondary piston 3 Primary piston 4 Stop bolt
8
Fig. 8.7 Sectional view of vacuum servo unit (Sec 9)
1 Master cylinder
2 Master cylinder
primary piston
3 Non-return valve
4 Front seal
5 Pushrod
6 Front chamber
7 Vacuum port
8 Plunger
9 Seal centraliser
10 Valve
11 Spring cup
12 Spring cup
13 Filter
14 Pushrod
15 Dust excluding
boot
16 Return spring
17 Valve spring
18 Valve cup
19 Rear seal
20 Seal
21 Cup
22 Rear chamber
23 Backing plate
24 Diaphragm
25 Vacuum piston
26 Front shell
27 Return spring
28 Cup
29 Guide bush
30 Seal
31 Rear shell
A = Projection of
pushrod above
vacuum cylinder
face
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3
1
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