wheel FIAT UNO 1983 Service Owner's Guide

Note the washers above and below the
contact assembly (photos).
23Fit the new contact assembly by reversing
the removal operations.
24Although the points gap is normally set in
production, check it using feeler blades when
the plastic heel of the movable arm is on a
high point of the shaft cam. Adjust if
necessary by inserting an Allen key (3.0 mm)
into the socket-headed adjuster screw.
25Carry out the operations described in
paragraphs 14 to 17 in this Section.
3 Dwell angle- checking
3
The dwell angle is the number of degrees
through which the distributor cam turns
between the instants of closure and opening
of the contact breaker points.
1Connect a dwell meter in accordance with
the maker’s instruction. The type of meter that
operates with the engine running is to be
preferred; any variation in contact breaker
gap, caused by wear in the distributor shaft or
bushes, or the height of the distributor cam
peaks, is evened out when using this.
2The correct dwell angle is given in the
Specifications at the beginning of this
Chapter. If the angle is too large, increase the
contact points gap. If the angle is too small,
reduce the points gap. Only very slight
adjustments should be made to the gap
before re-checking.3On Ducellier distributors, adjustment of the
dwell angle can only be carried out by
switching off the ignition, removing the
distributor cap, rotor and spark shield and
adjusting the points gap.
4Re-check once the engine is running.
Adjustment may have to be carried out
several times to obtain the correct dwell
angle.
5On Marelli distributors, adjustment of the
points gap (dwell angle) is carried out with the
engine running by inserting a 3.0 mm Allen
key in the hole provided in the distributor
body.
6Always check and adjust the dwell angle
before timing the ignition as described in
Section 4.
4 Ignition timing
3
1Timing the ignition on engines with
mechanical breaker distributors is carried out
in the following way.
2Disconnect the vacuum hose from the
distributor diaphragm capsule (photo).
3Have the engine at normal operating
temperature and idling with a stroboscope
connected in accordance with the
manufacturer’s instructions.
4Point the stroboscope at the timing marks
on the flywheel and the index on the aperture
on the flywheel housing. The mark on the
flywheel should be opposite to the BTDC
mark on the index specified for your particular
engine. Alternatively, use the notch on the
crankshaft pulley and the marks on the timing
belt cover (photo), but this will necessitate
removal of the wheel arch shield.
5If the marks are not in alignment, release
the distributor clamp plate and turn the
distributor gently until they are (photo).
6Tighten the clamp plate nut, switch off the
ignition, reconnect the vacuum hose and
remove the stroboscope.
7If there is any difficulty in seeing the timing
marks clearly, highlight them by painting with
quick-drying white paint.
4•4 Ignition system
4.4 Ignition timing marks on belt coverFig. 4.5 Flywheel housing timing marks
(Sec 4)4.2 Distributor vacuum hose
Fig. 4.4 Adjusting Marelli type contact
breaker points gap (Sec 2)
Fig. 4.3 Marelli contact breaker (Sec 2)
2.22B Washers above contact breaker2.22A Marelli contact breaker E-clip

5 Condenser (capacitor)-
removal, testing and refitting
1
The purpose of the condenser (sometimes
known as the capacitor) is to ensure that when
the contact breaker points open there is no
sparking across them which would weaken
the spark and cause rapid deterioration of the
points.
The condenser is fitted in parallel with the
contact breaker points. If it develops a short
circuit it will cause ignition failure as the points
will be prevented from interrupting the low
tension circuit.
1If the engine becomes very difficult to start
(or begins to misfire whilst running) and the
breaker points show signs of excessive
burning, suspect the condenser has failed
with open circuit. A test can be made by
separating the points by hand with the ignition
switched on. If this is accompanied by a
bright spark at the contact points, it is
indicative that the condenser has failed.
2Without special test equipment, the only
sure way to diagnose condenser trouble is to
replace a suspected unit with a new one and
note if there is any improvement.
3To remove the condenser from the
distributor, take out the screw which secures
it to the distributor body and disconnect its
leads from the terminals.
4When fitting the condenser, it is vital to
ensure that the fixing screw is secure. The
lead must be secure on the terminal with no
chance of short circuiting.
6 Distributor-
removal and refitting
3
1Remove the spark plug from No. 4 cylinder
and then turn the crankshaft either by
applying a spanner to the pulley nut or by
jacking up a front wheel, engaging top gear
and turning the wheel in the forward direction
of travel.
2Place a finger over the plug hole and feel
the compression being generated as the
piston rises up the cylinder bore.
3Alternatively, if the rocker cover is off,
check that the valves on No. 1 cylinder are
closed.
4Continue turning the crankshaft until the
flywheel and flywheel housing (BTDC) ignition
timing marks are in alignment. Number 4
piston is now in firing position.
5Remove the distributor cap and place it to
one side complete with high tension leads.
6Disconnect the distributor vacuum hose
and low tension lead (photo).
7Mark the distributor pedestal mounting
plinth in relation to the crankcase. Also mark
the contact end of the rotor in relation to the
rim of the distributor body.8Unbolt the clamp plate and withdraw the
distributor.
9Refit by having No. 4 piston at its firing
position and the distributor rotor and pedestal
marks aligned, then push the distributor into
position, mating it to the splined driveshaft.
10If a new distributor is being fitted then of
course alignment marks will not be available
to facilitate installation in which case, hold the
unit over its mounting hole and observe the
following.
903 cc engine: Distributor cap high tension
lead sockets pointing towards alternator and
at 90º to centre line of rocker cover. Contact
end of rotor arm pointing towards No. 4
contact in distributor cap (when fitted).
1116 cc and 1301 cc engine: Distributor
vacuum unit pointing downwards at 135º to
rear edge of timing belt cover. Contact end of
rotor arm pointing towards No. 4 contact in
distributor cap (when fitted).
11Tighten the distributor clamp bolt,
reconnect the vacuum hose and the low
tension leads. Refit the distributor cap. Screw
in the spark plug.
12Check the ignition timing as described in
Section 4.
7 Distributor (mechanical
breaker type)- overhaul
3
Ducellier
1The cap must have no flaws or cracks and
the HT terminal contacts should not be
severely corroded. The centre spring-loaded
carbon contact is renewable. If in any doubt
about the cap, buy a new one.
2The rotor deteriorates minimally, but with
age the metal conductor tip may corrode. It
should not be cracked or chipped and the
metal conductor must not be loose. If in
doubt, renew it. Always fit a new rotor if fitting
a new cap.
3With the distributor removed as described
in the preceding Section, take off the rotor
and contact breaker.4To remove the contact breaker movable
arm, extract the clip and take off the washer
from the top of the pivot post.
5Extract the screw and remove the fixed
contact arm.
6Carefully record the setting of the advance
toothed segment and then remove the spring
clip and vacuum capsule fixing screws and
withdraw the capsule with link rod.
7Pick out the lubrication pad from the recess
in the top of the distributor shaft. Unscrew the
screw now exposed.
8Mark the relationship of the cam to the
counterweight pins and then remove the cam
assembly.
9There is no way to test the bob weight
springs other than by checking the
performance of the distributor on special test
equipment, so if in doubt, fit new springs
anyway. If the springs are loose where they
loop over the posts, it is more than possible
that the post grooves are worn. In this case,
the various parts which include the shaft will
need renewal. Wear to this extent would mean
that a new distributor is probably the best
solution in the long run. Be sure to make note
of the engine number and any serial number
on the distributor when ordering.
10If the mainshaft is slack in its bushes or
the cam on the spindle, allowing sideways
play, it means that the contact points gap
setting can only be a compromise; the cam
position relative to the cam follower on the
moving point arm is not constant. It is not
practical to re-bush the distributor body
unless you have a friend who can bore and
bush it for you. The shaft can be removed by
driving out the roll pin from the retaining collar
at the bottom. (The collar also acts as an oil
slinger to prevent excess engine oil creeping
up the shaft.)
Marelli
11With the distributor removed from the
engine, take off the spark shield and rotor.
12Remove the contact breaker and carrier
as described in Section 2.
13Refer to paragraphs 9 and 10 for details of
counterweight springs and shaft bushes
(photo).
Ignition system 4•5
6.6 Distributor LT connection4.5 Distributor clamp plate nut
4

Reassembly
14This is a reversal of dismantling. On
Ducellier distributors, make sure that the
advance toothed segment is returned to its
original setting otherwise the advance curves
for your particular engine will be upset.
8 Ignition coil (mechanical
breaker ignition)
1Coils normally last the life of a car. The
most usual reason for a coil to fail is after
being left with the ignition switched on but the
engine not running. There is then constant
current flowing, instead of the intermittent
flow when the contact breaker is opening. The
coil then overheats, and the insulation is
damaged (photo).
2If the coil seems suspect after fault finding,
the measurement of the resistance of the
primary and secondary windings (usually an
ohmmeter) can establish its condition. If an
ohmmeter is not available, it will be necessary
to try a new coil.
9 Digiplex (electronic) ignition
- location of components and
precautions
1The main components of this system are
located within the engine compartment as
shown.
2On cars equipped with this system, it is
4•6 Ignition system
Fig. 4.7 Main components of Digiplex ignition system (Sec 9)8.1 Ignition coil
Fig. 4.6 Exploded view of typical Ducellier distributor (Sec 7)
1 Cap
2 Rotor
3 Movable breaker arm
4 Vacuum advance link
5 Fixed contact breaker arm
6 Contact breaker baseplate
7 Cam assembly8 Centrifugal advance weight
control springs
9 Driveshaft and plate
10 Body
11 LT insulator
12 Condenser
13 Vacuum capsule14 Cap retaining spring
15 Thrust washer
16 Spacer washer
17 Driving dog
18 Retaining pin
19 Felt pad
7.13 Marelli distributor centrifugal weights
and springs
1 Control unit
2 Cut-out control unit
3 Ignition coil
4 Flywheel (engine
speed) sensor
5 Crankshaft pulley
(TDC) sensor
6 Vacuum hose

important that the following precautions are
observed.
3Never start the engine if the battery leads
are loose.
4Do not stop the engine by pulling off a
battery lead.
5Remove the control unit if ambient
temperature (paint drying oven) is above 80ºC
(176ºF).
6Never connect or disconnect the multi-plug
at the control unit unless the ignition is
switched off.
7Disconnect the battery negative lead before
carrying out electric body welding.10 Digiplex (electronic) ignition
- checks and adjustments
3
1Without special equipment, any work on the
system components should be restricted to
the following.
Engine speed sensor
2The gap between the sensor and the teeth
of the flywheel should be between 0.25 and
1.3 mm (0.0099 to 0.0512 in). Any
deviation will be due to mechanical damage to
the sensor, no adjustment being possible.
TDC sensor
3The gap between the sensor and one of the
TDC reference marks on the crankshaft pulley
should be between 0.4 and 1.0 mm (0.016 to
0.039 in).
4Any deviation will be due to the sensor
plate becoming loose. To reposition it will
necessitate setting No. 1 piston at TDC which
can only be carried out accurately by your
dealer using special tools.
Supply circuit and continuity of
coil primary winding
5Connect a test lamp between contacts 11
and 9 of the multi-plug having first pulled it
from the control unit.
6Switch on the ignition, the test lamp should
come on. If it does not, either the connection
at the positive pole of the control unit or the
coil primary winding is open.
Control unit earth
7Connect a test lamp between contacts 8
and 9 of the multi-plug having first pulled it
from the control unit. Switch on the ignition,
the test lamp should come on. If it does not,
improve the earth connection.
11 Spark plugs
1
1The correct functioning of the spark plugs is
vital for the correct running and efficiency of the
engine. It is essential that the plugs fitted are
appropriate for the engine, and the suitable type
is specified at the beginning of this chapter. If
Ignition system 4•7
Fig. 4.9 Digiplex control unit (Sec 9)
1 Vacuum hose connector
2 Multi-plug socket
1 Control unit
2 Distributor
3 Ignition coil4 TDC sensor
5 Wiring connector plug6 Engine speed sensor
7 Wiring connector plug
Fig. 4.8 Location of Digiplex ignition system components (Sec 9)
Fig. 4.13 Test lamp connected between
terminals 8 and 9 of control unit multi-plug
(Sec 10)Fig. 4.12 Test lamp connected between
terminals 11 and 9 of control unit
multi-plug (Sec 10)
Fig. 4.11 TDC sensor gap (Sec 10)
Fig. 4.10 Engine speed sensor gap
(Sec 10)
4

this type is used and the engine is in good
condition, the spark plugs should not need
attention between scheduled replacement
intervals. Spark plug cleaning is rarely
necessary and should not be attempted unless
specialised equipment is available as damage
can easily be caused to the firing ends.
2At the specified intervals, the plugs should
be renewed. The condition of the spark plug
will also tell much about the overall condition
of the engine.
3If the insulator nose of the spark plug is
clean and white, with no deposits, this is
indicative of a weak mixture, or too hot a plug.
(A hot plug transfers heat away from the
electrode slowly - a cold plug transfers it away
quickly.)
4If the tip of the insulator nose is covered
with sooty black deposits, then this is
indicative that the mixture is too rich. Should
the plug be black and oily, then it is likely that
the engine is fairly worn, as well as the mixture
being too rich.
5The spark plug gap is of considerable
importance, as, if it is too large or too small
the size of the spark and its efficiency will be
seriously impaired. The spark plug gap should
be set to the gap shown in the Specifications
for the best results.
6To set it, measure the gap with a feeler
gauge, and then bend open, or close, the
outer plug electrode until the correct gap is
achieved. The centre electrode should never
be bent as this may crack the insulation and
cause plug failure, if nothing worse.
7When fitting new plugs, check that the plug
seats in the cylinder head are quite clean.
Refit the leads from the distributor in the
correct firing order, which is 1-3-4-2; No 1cylinder being the one nearest the flywheel
housing (903 cc) or timing belt (1116 or
1301 cc). The distributor cap is marked with
the HT lead numbers to avoid any confusion.
Simply connect the correctly numbered lead
to its respective spark plug terminal (photo).
12 Ignition switch-
removal and refitting
1
1Access to the steering column lock/ignition
switch is obtained after removing the steering
wheel and column shrouds (Chapter 10) and
the column switch unit (Chapter 9).
2In the interest of safety, disconnect the
battery negative lead and the ignition switch
wiring plug (photo).
3Insert the ignition key and turn to the STOP
position (photo).
4Pull the two leads from the switch.
5Turn the ignition key to MAR.
6Using a screwdriver depress the retaining
tabs (1) (Fig. 4.16) and release the ignition
switch.
7Set the switch cam (2) so that the notches
(3) are in alignment.
8Insert the switch into the steering lock and
engage the retaining tabs.
9Turn the ignition key to STOP and connect
the two leads.
10Reconnect the battery and refit the
steering wheel, switch and shrouds.
11Removal and refitting of the steeringcolumn lock is described in Chapter 10.
Note: The ignition key is removable when set
to the STOP position and all electrical circuits
will be off. If the interlock button is pressed,
the key can be turned to the PARK position in
order that the parking lamps can be left on
and the steering lock engaged, but the key
can be withdrawn.
4•8 Ignition system
Fig. 4.16 Typical ignition switch (Sec 12)
1 Retaining tabs 3 Alignment notches
2 Switch cam 4 Locating projection12.3 Ignition key positions
1 AVV (Start) 3 Stop (Lock)
2 Park (Parking lights on) 4 MAR (Ignition)12.2 Ignition switch and lock
11.7 Distributor cap HT lead markingsFig. 4.15 Spark plug connections on
1116 cc and 1301 cc engines (Sec 11)
Fig. 4.14 Spark plug connections on
903 cc engine (Sec 11)
It’s often difficult to insert spark plugs
into their holes without cross-threading
them. To avoid this possibility, fit a
short piece of rubber hose over the end
of the spark plug. The flexible hose
acts as a universal joint, to help align
the plug with the plug hole. Should the
plug begin to cross-thread, the hose
will slip on the spark plug, preventing
thread damage.

8
System type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dual-circuit hydraulic with servo unit and pressure regulating valve.
Discs front, drums rear. Handbrake mechanical to rear wheels.
Disc brakes
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single cylinder, sliding caliper
Disc diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227.0 mm (8.94 in)
Disc thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 to 10.9 mm (0.42 to 0.43 in)
Minimum regrind thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.0 mm (0.35 in)
Minimum wear thickness of pad friction material . . . . . . . . . . . . . . . . . . 1.5 mm (0.06 in)
Caliper cylinder diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48.0 mm (1.89 in)
Drum brakes
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single cylinder, with automatic adjusters
Drum internal diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185.24 to 185.53 mm (7.30 to 7.31 in)
Maximum regrind diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187.0 mm (7.37 in)
Minimum shoe lining friction material thickness . . . . . . . . . . . . . . . . . . . 1.5 mm (0.06 in)
Cylinder diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.05 mm (0.75 in)
Master cylinder bore diameter . . . . . . . . . . . . . . . . . . . . . . . . 19.05 mm (0.75 in)
Vacuum servo diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158.5 mm (6.0 in)
Hydraulic fluid type/specification . . . . . . . . . . . . . . . . . . . . . Hydraulic fluid to DOT 3 or 4, or SAE J1703C
System capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.33 litre (0.58 pint)
Torque wrench settingsNm lbf ft
Caliper mounting bracket bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 39
Rear wheel cylinder mounting bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7
Pressure regulating valve mounting bolts . . . . . . . . . . . . . . . . . . . . . . . 20 15
Master cylinder mounting nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 18
Rear brake backplate bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 15
Chapter 8 Braking system
For modifications, and information applicable to later models, see Supplement at end of manual
Brake disc - inspection, renovation or renewal . . . . . . . . . . . . . . . . . 6
Brake drum - inspection, renovation or renewal . . . . . . . . . . . . . . . . 8
Brake pedal - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Caliper - removal, overhaul and refitting . . . . . . . . . . . . . . . . . . . . . . 5
Disc pads - inspection and renewal . . . . . . . . . . . . . . . . . . . . . . . . . 3
Fault finding - braking system . . . . . . . . . . . . . . . . See end of Chapter
General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Handbrake - adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Handbrake cable - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Hydraulic hoses and pipes - inspection and renewal . . . . . . . . . . . . 11Hydraulic system - bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Master cylinder - removal, overhaul and refitting . . . . . . . . . . . . . . . 9
Pressure regulating valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Rear brake shoes - inspection and removal . . . . . . . . . . . . . . . . . . . 4
Rear wheel cylinder - removal, overhaul and refitting . . . . . . . . . . . . 7
Stop lamp switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Vacuum servo unit - description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Vacuum servo unit - removal and refitting . . . . . . . . . . . . . . . . . . . . 15
Vacuum servo unit - servicing and testing . . . . . . . . . . . . . . . . . . . . 14
8•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321

3.4 Removing the caliper unit
1 General description
The braking system is of four wheel
hydraulic type with discs on the front wheels
and drums on the rear.The hydraulic system is of dual-circuit type
and incorporates a pressure regulator valve to
limit pressure to the rear brakes during heavy
braking to prevent rear wheel lock up.
A vacuum servo unit is fitted to some
models.
The handbrake is mechanically operated on
the rear wheels.
2 Maintenance
1
1At the weekly service check, inspect the
fluid level in the master cylinder reservoir.
Topping up should only be required at very
infrequent intervals and should only be
necessary owing to the need for extra fluid in
the hydraulic system caused by wear of the
friction material of the disc pads and shoe
linings.
2The need for frequent or regular topping up
will be due to a leak in the system, probably
from a hydraulic cylinder seal or a flexible
hose. Correct the problem immediately.
3Use only clean new fluid for topping up. lt
must be of the specified type and have been
stored in a closed container and not have
been shaken for at least 24 hours (photo).
4At regular intervals, check the hoses and
pipelines for condition. Adjust the handbrake
if the lever travel becomes excessive. Check
the condition and security of the brake servo
vacuum hose. All these operations are
described later in this Chapter.
3 Disc pads-
inspection and renewal
2
1Jack up the front of the car and remove the
roadwheels.
2Extract the spring clips and slide out the
locking blocks (photos).
3On SX versions, carefully disconnect the
wear sensor lead connecting plug.
4Lift the caliper body from the disc and
inspect the thickness of the friction material
on each pad (photo). If it is 1.5 mm (0.06 in) or
less, renew the pads.
5Withdraw the pads and the anti-rattle
springs.
6Brush away any dust and dirt from the
caliper, taking care not to inhale the dust - this
contains asbestos and is thus potentially
injurious to health.
7As the new pads are thicker than the old
ones, the caliper piston must be depressed
8•2 Braking system
3.8A Disc pad and anti-rattle spring
Fig. 8.1 Components of the braking system (LHD shown) (Sec 1)
1 Caliper
2 Hose
3 Master cylinder
4 Fluid reservoir5 Cap and fluid level sensor
6 Vacuum servo unit
7 Rear wheel cylinder8 Pipeline
9 Hose
10 Pressure regulating valve
3.2B Removing a locking block
3.2A Removing a disc pad locking block
clip2.3 Fluid reservoir cap and float for
warning switch

into its cylinder to accommodate them. This
will cause the fluid level to rise in the reservoir.
Anticipate this by syphoning some out
beforehand, but take care not to let it drip
onto the paintwork - it acts as an effective
paint stripperl
8Refit the anti-rattle springs, the pads
(friction lining-to-disc), the cylinder body, the
locking blocks and their retaining clips
(photos).
9Refit the roadwheel and apply the footbrake
hard, several times, to bring the pads into
contact with the brake disc.
10Renew the pads on the opposite brake.
The pads should always be renewed in axle
sets.
11Top up the fluid reservoir.
4 Rear brake shoes-
inspection and renewal
2
1Jack up the rear of the car and remove the
roadwheels.
2Fully release the handbrake.
3Unscrew and remove the drum securing
bolts. One of these is a long locating spigot
for the roadwheel.
4Pull off the drum. lf it is tight, clean off the
rust at its joint with the hub flange, and apply
a little penetrating fluid. Two bolts may be
screwed into the drum securing bolt holes if
necessary and the drum thus eased off the
hub. The securing bolt holes are tapped for
this purpose.
5Brush away all the dust and dirt from the
shoes and operating mechanism, taking care
not to inhale it.
6The friction linings fitted as original
equipment are of the bonded type and the
rivet heads normally used as a guide to wear
are not, of course, fitted. However, if the
thickness of the friction linings is down to
1.5 mm (0.06 in) or less, the shoes must be
renewed. Always purchase new or factory
relined brake shoes.
7Before removing the brake shoes, note the
way in which the shoes are positioned, with
respect to leading and trailing ends (the end
of the shoe not covered by lining material).Note also into which holes in the shoe web
the return springs are connected. Sketch the
shoes or mark the holes on the new shoes
with quick drying paint if you are doubtful
about remembering (photo).
8Undo the steady springs by depressing and
rotating their caps a quarter turn to disengage
the slot from the pin. On later models a
U-shaped steady spring is used. Depress and
slide it out.
9Rotate the hub until the cut-outs in its rear
flange face are in alignment with the shoe
self-adjusters.
10Pivot the trailing shoe on the self-adjuster
post and disengage the ends of the shoe from
the slot in the wheel cylinder tappet and from
the lower anchor block.
11Work the shoe up the self-adjuster pivot
post until the self-adjuster boss enters the
cut-out in the hub flange. The shoe can now
be withdrawn (photo).
12Once off the self-adjuster post, the
pull-off spring tension is eased, as the shoe
can move towards the other, so the springs
can be unhooked.
13Remove the leading shoe in a similar way.
14The new shoes will already be fitted with
new self-adjusters.
15Fit the new shoes to their self-adjuster
posts, making sure that the handbrake shoe
lever is correctly located. Engage the ends of
the shoes.
16Using a wooden or plastic-faced mallet,
tap the shoes inwards against the friction of
their self-adjuster coil springs. This will havethe effect of reducing the overall diameter of
the shoes to facilitate fitting of the shoe return
springs and to allow the brake drum to slide
over them.
17Using pliers, reconnect the upper (longer)
and lower shoe return springs.
18Hold the steady pins in position from the
rear of the backplate. Fit the small coil springs
and the retaining cap, again using pliers to
grip the cap and to depress and turn it to
engage the pin. On later models fit the
U-shaped springs.
19Before refitting the drum, clean it out and
examine it for grooves or scoring (refer to
Section 8).
20Fit the drum and the roadwheel.
21Apply the brakes two or three times to
position the shoes close to the drum.
22Renew the shoes on the opposite brake in
a similar way.
23The handbrake should be automatically
adjusted by the action of the shoe adjuster. If
the handbrake control lever has excessive
travel, refer to Section 16 for separate
adjusting instructions.
5 Caliper- removal,
overhaul and refitting
4
Note: Purchase a repair kit in advance of
overhaul.
1Jack up the front roadwheel and remove it.
2Brush away all dirt from the caliper
Braking system 8•3
4.11 Rear hub showing cut-outs on rear
face for shoe self-adjuster bosses4.7 Rear brake assembly3.8B Cylinder body located on caliper
bracket
Fig. 8.2 Exploded view of caliper (Sec 5)
8

assembly and the flexible pipe, particularly the
fixing bracket and union at the car end of the
flexible pipe.
3Have ready a container suitable to catch
the brake fluid, and sheets of clean
newspaper on which to put parts.
4Take out the spring clips and locking
blocks, and take the caliper off the support
bracket.
5Disconnect 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.
6Remove the caliper to the bench or other
work surface, and clean it thoroughly with
hydraulic fluid or methylated spirit.
7Depress the piston until the dust excluding
boot can be removed.
8Now 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.
9Pick out the piston seal from its groove in
the cylinder. Use a sharp probe, but take care
to avoid scratching the cylinder bore.
10Examine 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.
11If 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.
12Lubricate the piston with clean hydraulic
fluid and insert it partially into the cylinder.
13Fit 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.
14Refit the caliper, reconnect the flexible
hose, then bleed the front hydraulic circuit
(refer to Section 12).
6 Brake disc- inspection,
renovation or renewal
2
1Whenever the front disc pads are being
checked for wear, take the opportunity to
inspect the discs for deep scoring or
grooving. After a high mileage the disc may
become reduced in thickness away from the
extreme outer edge of the disc. lf this wear is
rapid, it is possible that the friction pads are of
too hard a type.
2If the disc has evidence of many tiny cracks,
these may be caused by overheating due to a
seized caliper piston in the “applied” position.
3The foregoing conditions may be corrected
by regrinding the disc provided that the
thickness of the disc is not reduced below
that specified by such action. Alternatively, fit
a new disc.
4To remove a disc, take off the caliper andpads as described in Sections 3 and 5. Tie the
caliper up, out of the way.
5Knock back the tabs of the lockplates and
unbolt the caliper support bracket from the
hub carrier.
6Unscrew and remove the two bolts which
hold the disc assembly to the hub. One of
these bolts is for wheel locating purposes.
7Pull the disc from the hub.
8Refitting is a reversal of the removal
process. If the disc has excessive run-out,
repositioning it in relation to the hub may
bring it within tolerance by cancelling out the
run-out characteristics in the hub and disc,
once the most suitable fitted position has
been found.
7 Rear wheel cylinder-
removal, overhaul and refitting
4
Note: Purchase a repair kit in advance of
overhaul.
1If 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.
2Although 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. 3Remove the brake shoes, as described in
Section 4.
4Disconnect 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.
5Unscrew and remove the setscrews which
hold the cylinder to the backplate and
withdraw the cylinder. Prise off the rubber
dust excluding boots.
6Apply 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.
7Inspect 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.
8If 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.
9Manipulate the new seals into position,
using the fingers only for this job.
10Dip the pistons in clean hydraulic fluid and
insert them with the coil spring and washers
into the cylinder.
11Fit the new dust excluding boots.
12Refit the wheel cylinder to the backplate,
reconnect the hydraulic pipe, then refit the
shoes, the drum and the roadwheel.
13Bleed the rear hydraulic circuit as
described in Section 12.
8 Brake drum- inspection,
renovation or renewal
2
1Whenever the rear brake linings are being
checked for wear, take the opportunity to
inspect the internal surfaces of the brake
drums.
2If the drums are grooved or deeply scored,
they may be reground, provided that their new
internal diameter will not then exceed the
specified dimension. If it will, or the drum is
cracked, it must be renewed.
3Removal and refitting of a brake drum is
described in Section 4.
8•4 Braking system
Fig. 8.4 Exploded view of a rear wheel cylinder (Sec 7)
1 Pads
2 Dust excluder
3 Piston seal4 Piston
5 Cylinder body
Fig. 8.3 Sectional view of caliper (Sec 5)

their originally fitted sequence and note in
which direction the seal lips are located.
11Inspect the surfaces of the piston and
cylinder bore. If scoring, corrosion or
metal-to-metal rubbing areas are evident,
renew the master cylinder complete.
12If the components are in good condition,
discard the oil seals and manipulate the new
ones into position, using the fingers only.
13Refit by reversing the removal operations;
apply pressure to the piston ends so that the
stop bolts can be fitted, then tighten the end
plug. Make sure that the grooves in the
pistons engage in the stop bolts.
14Before refitting the master cylinder to the
servo, measure the projection of the servo
piston pushrod. When the master cylinder is
fitted, there must be a clearance (see A in
Fig. 8.7) between the end of the pushrod and
the primary piston end face of between 0.825
and 1.025 mm (0.03 and 0.04 in). A depth
gauge will be required for these
measurements, the reference point being the
mating surfaces of the master cylinder and the
vacuum servo.
15Alter the adjusting screw on the servo as
necessary and lock it by applying locking fluid
to the threads on completion.16Bolt the master cylinder to the vacuum
servo or bulkhead, then reconnect the
pipelines and reservoir cap leads.
17Bleed the complete hydraulic system, as
described in Section 12.
10 Pressure regulating valve
3
1The pressure regulating valve is a load
proportioning valve which restricts the
hydraulic pressure to the rear brakes
according to car weight during heavy
applications of the brake pedal. This prevents
the rear wheels locking.
2A faulty or non-operational valve should be
renewed complete, no repair being possible.
3To remove the valve, unscrew the pipe
unions and disconnect the hydraulic pipes
from the valve. Cap the ends of the pipes to
prevent loss of fluid.
4Unbolt the valve mounting bracket,
withdraw it and disconnect the tension spring
(photo).
5Refit the new valve and then adjust it in the
following way.
6Have the car standing on a level floor.
7The car should be normally loaded (kerb
weight) with fuel, oil, spare wheel etc. Load
the luggage compartment immediately behind
the seat back with:
65 kg (143 lbs) on three-door models or 55 kg (121 lbs) on five-door models
8Refer to Fig. 8.10 and slacken the valve
bracket securing bolt (1).
9Attach a 6.0 kg (13.2 lb) weight to the
bracket eye (2) as shown and then tighten the
bracket securing bolt.
10Bleed the braking system if a new valve
has been fitted. Bleeding will not of course be
required if only adjustment has been carried
out to an existing valve.11 Hydraulic hoses and pipes-
inspection and renewal
3
Flexible hoses
1Periodically, all brake pipes, pipe
connections and unions should be completely
and carefully examined.
2First examine for signs of leakage where the
pipe unions occur. Then examine the flexible
hoses for signs of chafing and fraying and, of
course, leakage. This is only a preliminary part
of the flexible hose inspection, as exterior
condition does not necessarily indicate the
interior condition, which will be considered
later.
3Flexible hoses are always mounted at both
ends in a rigid bracket attached to the body or
a sub-assembly. To remove them, it is
necessary first of all to unscrew the pipe
unions of the rigid pipes which go into them.
8•6 Braking system
Fig. 8.11 Typical hydraulic hose connection
(Sec 11)
Fig. 8.10 Weight attachment point for
pressure regulating valve adjustment (Sec 10)
1 Fixing bolt 2 Bracket eye
Fig. 8.9 Components of the pressure
regulating valve (Sec 10)
Fig. 8.8 Pressure regulating valve (Sec 10)10.4 Pressure regulating valve bracket and
tension spring