1983 FIAT UNO lock

4
System type
Except ES engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Battery, coil mechanical breaker distributor
ES engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Marelli Digiplex electronic with breakerless distributor
Firing order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 3 - 4 - 2 (No. 1 cylinder at crankshaft pulley end)
Mechanical breaker distributor
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Marelli or Ducellier
Contact breaker points gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.37 to 0.43 mm (0.015 to 0.017 in)
Condenser capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.25 µF
Dwell angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 to 58º
Rotor rotational direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clockwise
Ignition timing (dynamic)
903 cc engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5º BTDC at idle
1116 and 1301 cc engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10º BTDC at idle
Centrifugal advance:
903 cc engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Between 30 and 34º max
1116 and 1301 cc engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Between 22 and 24º max
Vacuum advance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Between 10 and 14º max
Ignition coil
Primary winding resistance at 20ºC (68ºF) . . . . . . . . . . . . . . . . . . . . . . . Between 2.6 and 3.3 ohms depending upon make of coil
Secondary winding resistance at 20ºC (68ºF) . . . . . . . . . . . . . . . . . . . . Between 6745 and 12 000 ohms depending upon make of coil
Marelli Digiplex electronic ignition
Rotor arm resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000 ohms
Advance range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Between 6 to 10º and 47 to 51º
Engine speed sensor
Resistance on flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612 to 748 ohms
Sensor to flywheel tooth gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25 to 1.3 mm (0.0099 to 0.0512 in)
TDC sensor
Resistance on pulley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612 to 748 ohms
Sensor to pulley tooth gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 to 1.0 mm (0.016 to 0.039 in)
Ignition coil
Primary winding resistance at 20ºC (68ºF) . . . . . . . . . . . . . . . . . . . . . . . 0.310 to 0.378 ohms
Secondary winding resistance at 20ºC (68ºF) . . . . . . . . . . . . . . . . . . . . 3330 to 4070 ohms
Chapter 4 Ignition system
For modifications and information applicable to later models, see Supplement at end of manual
Condenser (capacitor) - removal, testing and refitting . . . . . . . . . . . 5
Digiplex (electronic) - ignition checks and adjustments . . . . . . . . . . 10
Digiplex (electronic) ignition - location of components and
precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Distributor - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Distributor (mechanical breaker type) - overhaul . . . . . . . . . . . . . . . 7
Dwell angle - checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Fault finding - ignition system . . . . . . . . . . . . . . . . See end of Chapter
General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Ignition coil - (mechanical breaker ignition) . . . . . . . . . . . . . . . . . . . . 8
Ignition switch - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . 12
Ignition timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Mechanical contact breaker - points servicing . . . . . . . . . . . . . . . . . 2
Spark plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4•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

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.

Fault finding - mechanical breaker ignition system
Ignition system 4•9
4
Engine fails to start
m mLoose battery connections
m mDischarged battery
m mOil in contact points
m mDisconnected ignition leads
m mFaulty condenser
Engine overheats, lacks power
m
mSeized distributor weights
m mPerforated vacuum pipe
m mIncorrect ignition timing
Engine starts and runs but misfires
m
mFaulty spark plug
m mCracked distributor cap
m mCracked rotor arm
m mWorn advance mechanism
m mIncorrect spark plug gap
m mIncorrect contact points gap
m mFaulty condenser
m mFaulty coil
m mIncorrect timing
m mPoor engine/transmission earth connections
Fault finding - Digiplex (electronic) ignition system
Engine fails to start
m
mExcessive gap on TDC sensor
m mTDC or engine speed sensor short circuited or earthed
m mDefective ignition control unit
m mControl unit multi-plug contacts corroded
m mDefective coil
Engine lacks power, high fuel consumption
m
mIncorrect ignition advance
m mTDC sensor incorrectly set
m mDistributor vacuum hose blocked

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

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