1968 FIAT 500 Brake

2 Using Fiat puller A.46023 as shown in FIG 8 : 9
remove the wheel grease cap.
3 Using a universal t w o leg puller or Fiat puller A.40005
together w i t h items 1 and 9 remove the wheel hub/
drum assembly having first extracted the splitpin if
fitted and released the hub retaining nut (see FIG
8:10).
Dismantling brake unit:
1 Using a compressed air jet thoroughly clean all com-
ponents of the brake assembly.
2 Make a note of the location of the shoe return springs
and gently ease the shoes away from the brake
backplate (see FIG 10:2).
3 Disconnect the hydraulic line from the rear of t h e
wheel cylinder and remove the t w o cylinder retaining
bolts. Lift away the hydraulic cylinder.
Brake shoe lining:
Check the lining thickness and if found to be exces-
sively reduced service replacement shoes must be fitted.
The minimum allowable brake lining thickness is .059
inch.
Thoroughly check the linings for signs of oil or grease
which, if evident, the shoes must be renewed and the
drums and oil seals thoroughly inspected for the cause
of oil ingress and the cause remedied before reassembly.
Do not fit odd brake shoes and do not mix materials or
unbalanced braking will result.
Do not allow grease, oil or paint to contact the friction
linings.
Brake drums:
Whilst servicing the brakes, thoroughly inspect the
drums for scoring, ovality or distortion as well as inspect-
ing for minute hair line cracks. The drums may be refaced
by using a centre lathe and finally finishing by lapping
the drums to smooth out possible tool marks. The
maximum permissible oversize beyond the nominal drum
diameter of 6.702 to 6.712 inch is .039 inch. This limit
must never be exceeded otherwise the strength of the
drum will be impaired or a reduction in braking efficiency
caused by the increase of shoe expansion travel and the
consequent diminished contact pressure.
No brake adjustment will be required on the new 500
Saloon models after the drum has been reassembled as
the self-adjusting device will accommodate for the shoe
position to the new drum diameter during the first
operation of the brake pedal.
Reassembly of front brakes:
This is the reverse procedure to dismantling. Ensure
that the pull-off springs are correctly fitted to the holes in
the webs of the brake shoes and that the shoes register
correctly in the slotted ends of the pistons and the
side
mounting plate.
Upon assembly of the hub and brake drum assembly
liberally pack the space between the two bearings w i t h
Fiat MR grease, and remount the hub according to the
instructions in Chapter 8.
F500
FIG 10:3 Section view of left side f r o n t brake assembly
(500 Station Wagon)
Key to Fig 10:3 1 Wheel cylinder 2 Shoe return spring
3 Adjusting cams 4 Shoe guide pin 5 Shoe with lining
6 Drum 7 Housing flange
BRAKE SHOE
ADJUSTING DEVICE
SHOE WEDGE
SELF
WHEEL CYLINDER
SHOE RETURN SPRING
PARKING BRAKE
SHOE CONTROL
RETURN SPRINGS
LEVER
SHOE LOCK PLATEBRAKE SHOES
SHOE RETURN SPRING
SHOE MOUNTING PLATE
FIG 1 0:4 Right rear wheel brake assembly (500 Sedan)
10:4 Rear brakes
Rear brake drum removal:
1 Remove the wheel trims and carefully slacken the road
wheel retaining bolts. Using a garage hydraulic jack
raise the rear of t h e vehicle and place on firmly based
stands. Remove the road wheels.
2 Remove the four drum to hub retaining bolts and
spring washers and carefully withdraw the drum from
the backplate assembly.
Dismantling brake unit:
1 Using a compressed air jet thoroughly clean all
components of the brake assembly.
105

FIG 10:5 Section view of right side rear brake assembly
(500 Station Wagon)
FIG 10:6 Sectional view of a self-adjusting device for
automatic brake shoe-to-drum clearance take-up (500
Sedan)
Key to Fig 1 0 : 6 1 Pin 2 Friction washers 3 Load spring
4 Bushing 5 Shoe 6 Self-adjustment slot 7 Stud
2 Make a note of the location of the shoe return springs
and gently ease t h e shoes away from the backplate
(see FIG 10:4)
3 Disconnect the hydraulic line from the rear of t h e
wheel cylinder and also the shoe operating lever return
spring, the pin, washer and clevis from the lever so
releasing the handbrake inner operating cable.
4 Remove the t w o cylinder retaining bolts and lift away
the hydraulic cylinder.
106
Brake shoe linings:
Refer t o Section 10:3.
Brake drums:
Refer to Section 10:3.
Reassembly of rear brakes:
This is the reverse procedure to dismantling. Ensure
that the pull-off springs are correctly fitted to the holes
in the webs of the brake shoes and that the shoes
register in the slotted ends of the pistons and the side
mounting plate.
Carefully retract the position of the brake shoes and
ease t h e d r u m towards the hub ensuring that the four
bolt holes line up correctly. Replace the four bolts
together with their spring washers, reconnect the hand
brake cable. Refit road wheel and wheel trim.
10:5 Master cylinder
Operation:
Hydraulic fluid is admitted to the master cylinder
through hole 8 (see FIG 10:7), it seeps through the gap
between the valve carrier ring 17 and the master cylinder
dowel and flows through the valve carrier ring holes 15
so reaching the hydraulic lines, therefore filling the
system w i t h fluid. When the brake pedal is depressed the
plunger is moved forwards by the pushrod 12. This
forward action of the plunger 9 and valve carrier 17 brings
the valve 16 to rest against the valve front face. The
forward movement is continued so causing the valve ring
16 to pass over the compensation hole 5 and cutting off
communication with the fluid reservoirs. From this point
compression of the hydraulic fluid commences.
Hydraulic fluid acting on the front and inner faces of
the valve enables perfect valve sealing even under high
operation pressures. When the pressure reaches the fluid
in the wheel cylinders (see FIG 10:8) , it forces the
plungers 3 apart and through the plungers stems so
operating the brake shoes.
After releasing the brake pedal, the combined action
of the brake shoe and master cylinder plunger return
springs sends the fluid back to the master cylinder and
all parts resume their original position. The connection
between the hydraulic
system and the reservoir is
restored.
As there are no conventional valves fitted in the master
cylinder and the communication orifice between the
system a n d the reservoir is amply dimensioned the
bleeding operation is very straightforward.
Master cylinder removal:
1 Disconnect the stoplight cables from the pressure
operated switch.
2 Using a tapered w o o d plug of suitable size blank t h e
hole in the brake f l u i d reservoir.
3 Screw out the four front and rear cylinder brake fluid
delivery line connections at the master cylinder.
4 Remove the t w o master cylinder retaining nuts and
spring washers and carefully ease the hydraulic
cylinder from the body.

FIG 10:7 Master cylinder section
Key to Fig 10:7 1 Plug and spring seat 2 Body 3 Front wheel brake line duct 4 Plunger return spring
5 Compensating hole 6 Plug 7 Supply duct 8 Fluid inlet hole 9 Plunger 10 Plunger snap ring 11 Boot
12 Pushrod 13 Terminal, stoplight switch 14 Rear wheel brake line duct 15 Holes in floating ring carrier for fluid passage
16 Valve 17 Valve carrier 18 Seal
FIG 10:8 Wheel cylinder section
Key to Fig 10:8 1 Shoe actuating stems 2 Boot
3 Plungers 4 Fluid inlet hole 5 Seal rings
6 and 7 Spring thrust cups and plunger reaction spring
Apply the brakes hard for several minutes and inspect the
master cylinder and hydraulic connections for leaks.
10:6 Wheel cylinder operation
Hydraulic pressure from the master cylinder reaches
the fluid in the wheel cylinders by hydraulic pipes and it
forces the plungers 3 (see FIG 1 0 : 8) apart and through
the plungers the brake shoes operate. In the wheel
cylinders the sealing rings 5 are axially compressed by
the cup 6 under the action of the spring 7. The rings are
under the radial and axial action of hydraulic pressure
so that their sealing efficiency is increased as the
hydraulic pressure increases.
Checking wheel cylinders:
Once the wheel cylinders have been removed from
the brake backplate as previously described remove the
rubber boots 2 (see FIG 10:8) on the ends of the cylinder.
The plungers, brake shoe stems and sealing rings will be
pushed out due to normal spring expansion. Remove the
spring thrust cups and plunger reaction spring.
107F500
Master cylinder reassembly:
Ensure that the metal parts are clean. Dry off any
solvent used for cleaning. Renew all the rubber seals as
a matter of course. Wet the internal parts w i t h clean brake
fluid and reassemble them in the order shown in FIG
10:7.
Refitting the master cylinder:
Carefully locate the master cylinder flange to the body
panel ensuring that the pushrod 12 (see FIG 10:7)
correctly locates in the plunger 9. Secure the master
cylinder flange using the t w o nuts and spring washers.
Refit the hydraulic pipes.
Remove the tapered wooden plug from the reservoir
and bleed the system as described in Section 10:10. Dismantling master cylinder:
1 Refer to FIG 10 :7 and remove the plunger and rubber
boot from the cylinder body.
2 Using a pair of circlip pliers remove the plunger
circlip.
3 Carefully slide off from the inside of the cylinder body
the plunger, plunger seal, valve ring carrier, valve ring
and the reaction spring.
4 Remove the stoplight pressure operated switch.
5 Remove the cylinder body stop plug and upper plug.
6 Carefully inspect the master cylinder inner surface and
plunger outer surface to ensure that they have a mirror-
like finish and that the play between the two parts is
not excessive. Any roughness present on the cylinder
inner surface will necessitate renewing the complete
assembly. Scoring or corrosion of the surface will
quickly damage the rubber seals and can lead to
leakage of fluid and consequent partial or complete
brake failure. Check that the plunger return spring is not
corroded or distorted.

FIG 10:9 Brake fluid reservoir
Key to Fig 1 0 : 9 1 Reservoir 2 Strainer 3 Cap, vented
PARKING BRAKE CONTROL CABLE AND SHEATH
.CABLE ADJUSTING NUTS
SHOE OPERATING LEVER
LEVER RETURN SPRING
FIG 10:10 Parking brake control and adjusting mech-
anism at lefthand side rear wheel
Inspect the surfaces of the plungers and the cylinder
bore. If there is any roughness, scoring or corrosion the
assembly should be renewed. Check that the reaction
spring and thrust washers are not corroded or distorted,
renewing any defective parts.
Reassembling wheel cylinders:
Clean the metal parts thoroughly and dry off any
solvent used. The rubber parts should be renewed auto-
matically when servicing the cylinder. Wet the internal
parts w i t h clean brake f l u i d and reassemble them in the
order shown in FIG 10 : 8 .
10810:7 Self-adjusting device
The new 500 Sedan is equipped with a specially
designed brake shoe clearance self-adjusting device
which eliminates all need for manual adjustment during
service.
Operation:
On either side face of the brake shoe rim are placed t w o
friction washers in line with an adjustment slot which is
machined into the brake shoe (see FIG 10:6). The
friction washers are held against the shoe by a pin and
bush screw together through the slot with a strong
spring in between. The hollow pin fits onto the stud in the
brake housing flange. A clearance of .0315 inch between
the pin hole and stud permits the necessary movement of
the shoes to ensure proper braking under normal
operating conditions. On later models the self-adjuster
assembly is held together by a circlip.
When the shoe clearance adjustment is no longer
correct, the braking action will overcome the resistance of
the friction washers and drag along the shoes into contact
with the drum. Once the brake pedal has been released,
the action of the return springs will be weaker than the
friction of the adjustment washers on the shoes and so
the shoes will remain in the new position taken up. As
further wear of the linings occurs the shoes will again
automatically be repositioned by the device.
Inspection and assembly:
During normal brake overhaul all the components of
the self-adjusting device should be thoroughly checked
and any parts badly worn or damaged must be renewed.
Before reassembly it is advisable to check the spring
rating using Fiat tester A.11493 by
compressing the
spring to a height of .374 inch which should give a
corresponding load reading of 97 ± 4.9 Ib. To re-
assemble the device after testing proceed as follows:
1 Place the pin of the self-adjusting device on support
A.54002/2 and insert first the friction washer followed
by the shoe, the second friction washer, the load spring
and the bushings.
2 Fit wrench A.54002/1 onto the support and by
exerting a slight pressure to overcome the spring load
fully tighten the bush onto the pin. Lock the pin and
bushing using a centre punch. Alternatively, fit the
circlip.
3 Install the shoes onto the brake housing flange and
hook up the t w o return springs. Move the shoes out-
wards as far as they will go and release them. Check
that during the return of the shoes the friction washers
have stayed in their new position.
10:8 Removing a flexible hose
Never try to release a flexible hose by turning the ends
w i t h a spanner. The correct procedure is as follows:
Unscrew the metal pipeline union nut from its con-
nection with the hose. Hold the adjacent hexagon on the
hose w i t h a spanner and remove the locknut which
secures the hose to the brackets. The hose can now be
turned without twisting the flexible part, by using a
spanner on the hexagon at the other end.
1
2
3

10:9 Brake fluid reservoir
The reservoir is located in the front compartment to the
side of the fuel tank as shown in FIG 10:9. Should it be
necessary to detach the fluid outlet line from the reservoir
the outlet hole must be blanked off using a tapered
wooden peg of suitable length so that the cap may be
replaced to prevent the ingress of foreign matter into
the reservoir and the absorbtion of moisture, oil or petrol
vapours which would alter the properties of the hydraulic
fluid.
A special filter is fitted into the top of the reservoir
through which all fluid used for topping-up the reservoir
must pass to ensure utmost inner cleanliness of the
hydraulic system.
10:10 Bleeding the system
This is not a routine maintenance operation and is only
necessary if air has entered the hydraulic system because
parts have been dismantled or because the f l u i d level in
the reservoir has dropped so low that air has been drawn
into the main feed pipe to the master cylinders.
1 Fill the reservoir w i t h Fiat 'Blue Label' hydraulic fluid.
During the bleeding operation fluid will be used and
constant topping-up of the supply reservoir will be
needed. If this is not done it is possible for air to enter
the master cylinder main feed pipe which will nullify
the operation and necessitate a fresh start.
2 Attach a length of rubber or plastic tubing to the
bleeder screw on the rear wheel cylinder furthermost
from the master cylinder. Immerse the free end of the
tube in a small volume of hydraulic brake fluid in a
clean jar.
3 Open the bleed screw one turn and get a second
operator to press down slowly on the brake pedal. After
a full stroke let the pedal return without assistance,
pause a moment and repeat the d o w n stroke. At first
there will be air bubbles issuing from the bleed tube,
but when fluid alone is ejected, hold the pedal firmly
down on the floor panel and tighten the bleed screw.
Repeat this operation on the other rear brake and then
repeat the operation on the two front brakes.
4 On completion, top-up the fluid in the reservoir to the
correct level. Discard all dirty fluid. If fluid is perfectly
clean, let it stand for twenty four hours to become
clear of air bubbles before using it again.
10:11 Hand parking brake
Normally with the new 500 Sedan model automatic
brake adjusting device, adjustment of the rear brakes
will take up excessive handbrake travel.
If there is excessive travel on the handbrake of the
Sedan model at any time, or in the case of Station Wagon
model even after the rear brakes have been manually
adjusted, suspect worn brake shoe linings or stretched
handbrake cables. Examine the linings and fit replace-
ment shoes if necessary. Check the action of the hand
parking brake again and if there is still too much travel
before the brakes are applied it is permissible to take up as
follows:
1 It is essential to ensure that the rear shoes are correctly
adjusted as described in Section 10:2.
2 Apply the hand parking brake lever until the pawl
engages with the ratchet at the second notch.
F500
FIG 10:11 An exploded view showing the components of
the tandem master cylinder
3 Jack up the rear of t h e vehicle and place on firmly
based stands.
4 Locate the cable adjusting nuts as shown in FIG
10:10 and adjust these until it is just possible to turn
the road wheels by heavy hand pressure. It is important
that both wheels offer the same resistance to turning
to obtain correctly balanced braking.
5 Return the lever to the OFF position and check that
both wheels are quite free to rotate. If a brake tends to
bind, remove the wheel and brake drum and check
the brake shoe pull-off spring is correctly fitted and
that the lever return spring and operating lever are
functioning correctly. Also check for suspected
seizure of the wheel cylinder. When the fault has
been rectified refit the drum. Readjust and recheck.
Removing the hand parking brake cable:
1 Chock the front wheels and release the handbrake.
Raise t h e rear of the vehicle and place on firmly based
stands.
2 Disconnect the cables from the operating levers on
each rear brake unit. Release each cable from its body
mounted bracket.
3 Inside the car, remove the rear seat and the seat belt
fitting from the floor. As necessary, remove the centre
console and the carpet to give access to the cover plate
on the centre tunnel and remove it.
4 Remove the handbrake lever assembly, detach the
cable compensator and pull the cables through the
holes in the box panel.
5 Reassembly is the reverse procedure to removal.
Ensure t h a t the cable is well lubricated and finally
readjust as previously described.
10:12 The dual circuit braking system
This is used on later model cars. A tandem master
cylinder provides t w o entirely separate hydraulic circuits,
one for the front and one for the rear brakes. The
components of the master cylinder are shown in the
exploded view of FIG 1 0 : 1 1 . The principle of operation is
quite straightforward and easy to understand.
169

When the pedal is applied, it moves the rear (primary)
piston to pressurise the front brakes through the rear port.
This, in turn, forces the front (secondary) piston down the
bore to pressurise the rear brake circuit through the front
port. In the event of a failure in the primary circuit, the
primary piston moves into direct contact with the second-
ary piston and full braking is still available on the rear
wheels. If a leak occurs in the rear circuit, the secondary
piston is moved to the end of the bore, sealing off the out-
let port and full braking pressure is applied to the t w o front
brakes.
With two fluid reservoirs connected to the inlets 3 and 5
the two circuits are fully independent.
The remaining components in the braking system are
similar to those used in the earlier single circuit layout.
10:13 Fault diagnosis
(a) 'Spongy' pedal
1 Leak in t h e system
2 Worn master cylinder
3 Leaking wheel cylinders
4 Air in the system
5 Gaps between shoes and underside of linings
110
(b) Excessive pedal movement
1 Check 1 and 4 in (a)
2 Excessive lining wear
3 Very low fluid level in supply reservoir
4 Too much free movement of pedal
(c) Brakes grab or pull to one side
1 Brake backplate loose
2 Scored, cracked or distorted drum
3 High spots on drum
4 Unbalanced shoe adjustment
5 Wet or oily linings
6 Worn or loose spring fixings
7 Front suspension or rear suspension anchorages
loose
8 Worn steering connections
9 Mixed linings of different grades
10 Uneven tyre pressure
11 Broken shoe return springs
12 Seized handbrake cable