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Refitting
6 Refitting is a reversal of removal, but note
that the nose of the unit must face forwards
and be inclined upwards at an angle of 22° to
the horizontal. Provided that the mounting
bracket is undamaged, this angle will
automatically be achieved. Finally bleed the
rear hydraulic circuit, as described in Section 2.
1.9 GTI models
General information
7 On 1.9 GTI models, the hydraulic circuit is
split diagonally and two compensators are
fitted. Each compensator is located in the rear
circuit near the rear wheel (see illustration).
They are of fixed calibration, and not
load-sensitive.
Removal
8 To minimise fluid loss, unscrew the master
cylinder reservoir filler cap and place a piece
of polythene over the filler neck. Secure the
polythene with an elastic band ensuring that
an airtight seal is obtained.
9 Chock the front wheels then jack up the
rear of the car and support it on axle stands
(see “Jacking and vehicle support”).
10 Unscrew the union nuts and disconnect
the rigid hydraulic lines from each end of the
unit while holding the unit on the flats
provided. Ease out the pipes and remove the
compensator from under the car.
11 Note that from December 1988, modified
compensators have been fitted. The modified
components can be identified by the letter on
the compensator body. Early components
have the identifying letter “F”, while later
components have the identifying letter “E”.
The later components can be used to replace
the early components, but both
compensators must be of the same type.
Refitting
12 Refitting is a reversal of removal. Bleed
the relevant hydraulic circuit, as described in
Section 2 on completion.
14 Vacuum servo unit - testing,
removal and refitting
3
Testing
1 With the engine switched off, depress the
brake pedal several times. The distance by
which the pedal moves should now alter over
all applications.
2 Depress the brake pedal fully and hold it
down then start the engine. The pedal should
be felt to move downward slightly.
3 Hold the pedal depressed with the engine
running, switch off the ignition and continue to
hold the pedal depressed for 30 seconds
during which period the pedal should neither
rise nor drop.
4 Start the engine whilst the brake pedal is
released, run it for a minute and switch off.
Give several applications of the brake pedal.
The pedal travel should decrease with each
application.
5 Failure of the brake pedal to act in the way
described will indicate a fault in the servo unit.
6 The servo unit should not be serviced or
overhauled beyond the operations described
in this Section and in the event of a fault
developing, renew the servo complete.
7 Periodically check the condition of the
vacuum hose and security of the clips.
8 Renew the hose if necessary.
9 If the servo hose right-angled non-return
valve is loose in its sealing grommet, or if the
grommet shows evidence of cracking or
perishing, renew it. Apply some hydraulic fluid
to the rubber to facilitate fitting.
Air filter renewal
10 Although not a specified operation, the air
filter through which the pushrod passes at the
rear of the servo can become clogged after a
high mileage. Disconnect the rod from the
pedal, cut the filter diagonally having slipped
the dust excluder off the rod. Fit the new filter.
Servo unit removal
11 Remove the master cylinder, as described
in Section 12. Disconnect the servo vacuum
hose.
12 Working inside the car, disconnect the
pushrod from the brake pedal; noting that it is
on the lower hole.
13 Unscrew the mounting nuts behind the
pedal bracket then withdraw the servo unit into
the engine compartment. Remove the gasket.
Servo unit refitting
14 Before fitting a servo unit, check the
pushrod dimensions and adjust where
possible (see illustration).
15 Refitting is a reversal of removal, but fit a
new gasket and fully tighten the mounting
nuts. Note that the pushrod is fitted to the
lower hole of the two on the brake pedal. Refer
to Section 12 when refitting the master
cylinder. Finally, with the brake pedal released,
check that the clearance between the stop
light switch threaded shank and pedal is 3.5
mm. If necessary loosen the locknuts, adjust
the switch and tighten the locknuts.
Braking system 9•13
9
13.7 Rear brake compensator fitted to
1.9 GTI models
14.14 Cross-section of the vacuum
servo unit showing pushrod
adjustment dimensions
1 Adjustment screw
A = 22.2 to 22.4 mm
B = 86.5 to 89.5 mm