brakes FIAT UNO 1983 Service Repair Manual

REPAIRS & OVERHAUL
Engine and Associated Systems
Engine (also see Chapter 13)Page 1•1
Cooling and heating systems (also see Chapter 13)Page2•1
Fuel system (also see Chapter 13)Page 3•1
Ignition system (also see Chapter 13)Page4•1
Transmission
Clutch (also see Chapter 13)Page5•1
Transmission (also see Chapter 13)Page6•1
Driveshafts, hubs, roadwheels and tyres (also see Chapter 13)Page7•1
Brakes
Braking system(also see Chapter 13)Page 8•1
Electrical
Electrical system(also see Chapter 13)Page 9•1
Steering and suspension
SteeringPage 10•1
Suspension (also see Chapter 13)Page 11•1
Bodywork
Bodywork (also see Chapter 13)Page 12•1
Additional information
Supplement: Revisions and information on later models Page 13•1
Wiring DiagramsPage 14•1
REFERENCE
MOT Test Checks PageREF•1
Tools and Working Facilities Page REF•5
General Repair Procedures Page REF•8
Fault FindingPage REF•9
Buying Spare Parts & Vehicle Identification Numbers PageREF•12
Glossary of Technical Terms PageREF•13
IndexPage REF•17
Contents

Fig. 1.20 Flywheel housing cover plate
removed (Sec 13)
Fig. 1.19 Left-hand flexible
mounting (Sec 13)
10Disconnect the leads from the reversing
lamp switch.
11Disconnect the coolant hoses from the
cylinder head and coolant pump.
12Disconnect the fuel inlet hose from the
fuel pump. Plug the hose.
13Disconnect the throttle and choke
controls from the carburettor.
14Disconnect the heater hoses from the
engine.
15Disconnect the fuel return hose from the
carburettor.
16Disconnect the exhaust downpipe from
the manifold.
17Raise the front end of the car and support
it securely on axle stands. Remove the
roadwheels.
18Unscrew the driveshaft to hub nuts. These
are very tight and a long knuckle bar will be
required when unscrewing them. Have anassistant apply the brakes hard to prevent the
hub turning.
19Working under the car, remove the
protective shields and disconnect the exhaust
system mountings and withdraw it to the
rear.
20Disconnect the forward ends of the
gearchange rods by prising their sockets from
the ballstuds.
21Unscrew the nuts on the steering tie-rod
end balljoints and using a suitable “splitter”
tool separate the balljoints from the steering
arms. Unbolt the brake calipers and tie them
up out of the way.
22Unscrew and remove the bolts which
secure the hub carriers to the U-clamps at the
base of the suspension struts (photo).
23Pull the tops of the hub carriers from the
clamps and release the driveshafts from the
hub carriers.24Tie the driveshafts in a horizontal plane
with lengths of wire.
25Support the engine on a hoist or use a
trolley jack under the engine/transmission and
remove the bottom mounting and then the
upper left and right-hand ones (photo).
26Carefully lower the power unit to the floor
and withdraw it from under the car.
27External dirt and grease should now be
removed using paraffin and a stiff brush or a
water-soluble solvent.
28Unbolt and remove the engine mounting
brackets and the starter motor.
29Unbolt and remove the cover plate and
gearchange ball stud strut from the lower front
face of the flywheel housing.
30With the engine resting squarely on its
sump pan unscrew the flywheel housing
connecting bolts noting the location of any
lifting lugs and hose and wiring brackets.
1•14 903 cc engine
13.25 Right-hand engine mounting
Fig. 1.18 Hub carrier detached
from strut clamp (Sec 13)
13.22 Hub carrier strut clamp
Fig. 1.17 Tie-rod end balljoint
disconnected (Sec 13)Fig. 1.16 Gearchange rods
disconnected (Sec 13)
Fig. 1.15 Fuel return hose
disconnected from carburettor
(Sec 13)Fig. 1.14 Fuel inlet hose
disconnected from pump
(Sec 13)Fig. 1.13 Coolant hose at rear
of coolant pump (Sec 13)Fig. 1.12 Coolant hoses at
thermostat housing (Sec 13)

Fault finding - all engines
Note: When investigating starting and uneven running faults, do not be tempted into snap diagnosis. Start from the beginning of the check
procedure and follow it through. It will take less time in the long run. Poor performance from an engine in terms of power and economy is not
normally diagnosed quickly. In any event, the ignition and fuel systems must be checked first before assuming any further investigation needs to
be made.
All engines 1•35
1
Engine fails to turn when starter operated
m mBattery discharged
m mBattery terminals loose or corroded
m mBattery earth to body defective
m mEngine/transmission earth strap broken or loose
m mDisconnected or broken wire in starter circuit
m mIgnition/starter switch defective
m mStarter motor or solenoid defective (see Chapter 9)
m mMajor mechanical failure (seizure) or long disuse (piston rings rusted
to bores)
Engine turns and fails to start
m mBattery discharged
m mBattery terminals loose or corroded
m mBattery or engine earth strap loose
m mStarter motor connections loose
m mOil in engine/transmission too thick
m mStarter motor defective
m mVapour lock in fuel line (in hot conditions or at high altitude)
m mBlocked float chamber needle valve
m mFuel pump filter blocked
m mChoked or blocked carburettor jets
m mFaulty fuel pump
m mFuel tank empty
m mOther fuel system fault (see Chapter 3)
m mShorted or disconnected low tension leads
m mDirty, incorrectly set, or pitted contact breaker points
m mContact breaker point spring earthed or broken
m mFaulty condenser
m mDefective ignition switch
m mFaulty coil
m mDamp or dirty HT leads, distributor cap or plug bodies
m mBroken, loose or disconnected LT leads
m mIgnition leads connected wrong way round
m mOther ignition fault (see Chapter 4)
m mValve timing incorrect (after rebuild)
Engine fires but will not run
m
mInsufficient choke (cold engine)
m mFuel starvation or tank empty
m mIgnition fault (see Chapter 4)
m mOther fuel system fault (see Chapter 3)
Engine stalls and will not restart
m
mToo much choke allowing too rich a mixture to wet plugs
m mFloat damaged or leaking or needle not seating
m mFloat lever incorrectly adjusted
m mIgnition failure - sudden
m mIgnition failure - misfiring precedes total stoppage
m mIgnition failure - in severe rain or after traversing water splash
m mNo petrol in petrol tank
m mPetrol tank breather choked
m mSudden obstruction in carburettor
m mWater in fuel system
Engine slow to warm up
m
mChoke linkage maladjusted
m mAir cleaner temperature control unit defective
m mThermostat stuck open (see Chapter 2)
m mOther fuel system fault (see Chapter 3)
Difficult starting when cold
m
mInsufficient choke
m mFouled or incorrectly gapped spark plugs
m mDamp or dirty HT leads, distributor cap or spark plug bodies
m mDirty or maladjusted contact breaker points
m mOther ignition fault or timing maladjustment (see Chapter 4)
m mFuel system or emission control fault (see Chapter 3)
m mPoor compression (may be due to incorrect valve clearances, burnt
or sticking valves, blown head gasket, worn or damaged pistons,
rings or bores)
m mIncorrect valve timing (after rebuild)
Difficult starting when hot
m
mIncorrect use of manual choke
m mFuel line vapour lock (especially in hot weather or at high altitudes)
m mIncorrect ignition timing
m mOther fuel system or emission control fault (see Chapter 3)
m mPoor compression (see above)
Engine lacks power
m
mIgnition timing incorrect
m mContact breaker points incorrectly gapped
m mIncorrectly set spark plugs
m mDirty contact breaker points
m mDistributor automatic advance and retard mechanisms not
functioning correctly
m mOther ignition system fault (see Chapter 4)
m mAir cleaner choked
m mCarburation too rich or too weak
m mFuel filter blocked
m mAir filter blocked
m mFaulty fuel pump giving top and fuel starvation
m mOther fuel system fault (see Chapter 3)
m mPoor compression
m mValve clearances incorrect
m mCarbon build-up in cylinder head
m mSticking or leaking valves
m mWeak or broken valve springs
m mWorn valve guides or stems
m mWorn pistons and piston rings
m mBurnt out valves
m mBlown cylinder head gasket (accompanied by increase in noise)
m mWorn pistons and piston rings
m mWorn or scored cylinder bore
m mBrakes binding
Engine misfires throughout speed range
m
mDefective or fouled spark plug
m mLoose, cracked or defective HT lead
m mMaladjusted, sticking or burnt valves
m mIgnition timing incorrect
m mBlown head gasket
m mFuel contaminated
m mOther ignition fault (see Chapter 4)
m mOther fuel system fault (see Chapter 3)
Poor engine braking
m
mHigh idle speed
m mOther fuel system fault (see Chapter 3)
m mLow compression

Fault finding - cooling and heating systems
2•8 Cooling and heating systems
Overheating
m mInsufficient coolant in system
m mPump ineffective due to slack drivebelt
m mRadiator blocked either internally or externally
m mKinked or collapsed hose causing coolant flow restriction
m mThermostat not working properly
m mEngine out of tune
m mIgnition timing retarded or auto advance malfunction
m mCylinder head gasket blown
m mEngine not yet run-in
m mExhaust system partially blocked
m mEngine oil level too low
m mBrakes binding
Engine running too cool
m
mFaulty, incorrect or missing thermostat
Loss of coolant
m
mLoose hose clips
m mHoses perished or leaking
m mRadiator leaking
m mFiller/pressure cap defective
m mBlown cylinder head gasket
m mCracked cylinder block or head
Heater gives insufficient output
m
mEngine overcooled (see above)
m mHeater matrix blocked
m mHeater controls maladjusted or broken
m mHeater control valve jammed or otherwise
defective

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

9 Master cylinder- removal,
overhaul and refitting
4
Note: Purchase a repair kit in advance of
overhaul.
1The 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).
2Cover 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.
3Detach the leads from the terminals on the
reservoir cap, then unscrew and remove the
cap and float.
4Unscrew 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.
5Unscrew the mounting nuts and withdraw
the master cylinder from the bulkhead or from
the servo unit.
6Clean away all external dirt and tip out the
fluid from the reservoir and cylinder body.
7The fluid reservoirs need not be removed
from the master cylinder but if they are, renew
the rubber sealing collars when refitting.
8Grip the master cylinder in a vice, then
unscrew and remove the end plug. Catch the
coil spring.
9Using a thin rod, apply pressure to the end
of the primary piston then unscrew and
remove the two stop bolts and sealing
washers.
10The 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 brakes7 Spring and cup
8 Inlet from reservoir
9 Primary piston
10 Seal
12 Stop bolts13 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
8Fig. 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 spring18 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
2
3
1
4

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

The hose ends can then be unclipped from
the brackets. The mounting brackets,
particularly on the body frame, are not very
heavy gauge and care must be taken not to
wrench them off (photo).
4With the flexible hose removed, examine
the internal bore. If it is blown through first, it
should be possible to see through it. Any
specks of rubber which come out, or signs of
restriction in the bore, mean that the inner
lining is breaking up and the pipe must be
renewed.
5When refitting the flexible hoses check they
cannot be under tension, or rub, when the
wheels are at the full range of suspension or
steering movement.
6Bleed the system (see Section 12) on
completion.
Rigid pipes
7Inspect the condition of the braking system
rigid pipelines at frequent intervals. They must
be cleaned off and examined for any signs of
dents (or other percussive damage) and rust
and corrosion. Rust and corrosion should be
scraped off and, if the depth of pitting in the
pipes is significant, they will need renewal.
This is particularly likely in those areas
underneath the car body and along the rear
axle where the pipes are exposed to the full
force of road and weather conditions.
8Rigid pipe removal is usually straight-
forward. The unions at each end are undone,
the pipe and union pulled out, and the centre
sections of the pipe removed from the body
clips where necessary. Underneath the car,
exposed unions can sometimes be very tight.
As one can use only an open-ended spanner
and the unions are not large, burring of the
flats is not uncommon when attempting to
undo them. For this reason, a self-locking grip
wrench (Mole) is often the only way to remove
a stubborn union.
9Rigid pipes which need renewal can usually
be purchased at any garage where they have
the pipe, unions and special tools to make
them up. All they need to know is the total
length of the pipe, the type of flare used at
each end with the union, and the length and
thread of the union. Fiat is metric, remember.
10Fitting your new pipes is a straightforwardreversal of the removal procedure. If the rigid
pipes have been made up, it is best to get all
the sets bends in them before trying to fit
them. Also, if there are any acute bends ask
your supplier to put these in for you on a tube
bender. Otherwise, you may kink the pipe and
thereby restrict the bore area and fluid flow.
11Bleed the system (see Section 12) on
completion.
12 Hydraulic system-
bleeding
3
1If the master cylinder or the pressure
regulating valve has been disconnected and
reconnected then the complete system (both
circuits) must be bled.
2If a component of one circuit has been
disturbed then only that particular circuit need
be bled.
3The two disc brakes comprise the front
circuit and the two rear brakes the rear circuit.
4Unless the pressure bleeding method is
being used, do not forget to keep the fluid
level in the master cylinder reservoir topped
up to prevent air from being drawn into the
system which would make any work done
worthless.
5Before commencing operations, check that
all system hoses and pipes are in good
condition with all unions tight and free from
leaks.
6Take great care not to allow hydraulic fluid
to come into contact with the vehicle
paintwork as it is an effective paint stripper.
Wash off any spilled fluid immediately with
cold water.
7As the system on 55 and 70 models
incorporates a vacuum servo, destroy the
vacuum by giving several applications of the
brake pedal in quick succession. The car
should be loaded with enough weight to
actuate the pressure regulating valve before
bleeding commences.
Bleeding - two man method
8Gather together a clean glass jar and a
length of rubber or plastic tubing which will be
a tight fit on the brake bleed screws (photo).9Engage the help of an assistant.
10Push one end of the bleed tube onto the
flrst bleed screw and immerse the other end
of the glass jar which should contain enough
hydraulic fluid to cover the end of the tube.
11Open the bleed screw one half a turn and
have your assistant depress the brake pedal
fully then slowly release it. Tighten the bleed
screw at the end of each pedal downstroke to
obviate any chance of air or fluid being drawn
back into the system.
12Repeat this operation until clean hydraulic
fluid, free from air bubbles, can be seen
coming through into the jar.
13Tighten the bleed screw at the end of a
pedal downstroke and remove the bleed tube.
Bleed the remaining screws in a similar way.
Bleeding - using a one way
valve kit
14There are a number of one-man, one-way
brake bleeding kits available from motor
accessory shops. It is recommended that one
of these kits is used wherever possible as it will
greatly simplify the bleeding operation and also
reduce the risk of air or fluid being drawn back
into the system quite apart from being able to
do the work without the help of an assistant.
15To use the kit, connect the tube to the
bleedscrew and open the screw one half a
turn.
16Depress the brake pedal fully and slowly
release it. The one-way valve in the kit will
prevent expelled air from returning at the end
of each pedal downstroke. Repeat this
operation several times to be sure of ejecting
all air from the system. Some kits include a
translucent container which can be positioned
so that the air bubbles can actually be seen
being ejected from the system.
17Tighten the bleed screw, remove the tube
and repeat the operations on the remaining
brakes.
18On completion, depress the brake pedal. If it
still feels spongy repeat the bleeding operations
as air must still be trapped in the system.
Bleeding - using a pressure
bleeding kit
19These kits too are available from motor
accessory shops and are usually operated by
air pressure from the spare tyre.
Braking system 8•7
12.8 Caliper bleed screw with dust cap
fittedFig. 8.12 Bleeding a rear wheel cylinder
(Sec 12)11.3 Front hydraulic hose bracket
8