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176
FIAT - 850 PASSENGER CARS
1
5
6
l
5
1
Wheel Cylinders.
The wheel cylinders have the following bores:
- front
_ _ _ _ _
_ _ _ _ _ _
7/8"
-
rear
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3/4"
Tightness in cylinders is obtained by means of
a pair of rubber seal rings (5, fig. 289) which will
stretch under impending fluid pressure.
These
seal rings are pressed against pistons by two back-
ing washers to which reaction spring (6) is clenched;
pistons operate brake shoes through stems.
Inspection and Repair.
FLUID RESERVOIR AND LINES
NOTE - Use only FIAT special
«
blue label» fluid
to clean brake lines and reservoir lest seals may
be ruined and system operation adversely affected.
II
II
10
9
8
~
/
6
7
//
L
5
Fig. 291
~
Sectional view of right side rear wheel.
(Up to car with No. for spare 802091).
1.
Nut holding hub and brake backing plate•• 2. Brake backing
plate with nut, pin and cam for shoe clearance adjustment. •
3. Brake shoe with lining. - 4. Brake drum. - 5. Brake drum screw.
~
6. Wheel hub and bearings.
~
7. Wheel shaft. - 8. Shoe return
spring. - 9. Pin.
~
10. Outer cup.
~
11. Shoe guide spring.
~
12. Inner
cup.
~
13. Control arm.
When overhauling service brakes, check for
ab~
sence of foreign matter or sludge deposits in fluid
reservoir and for a restricted vent hole in reser-
voir cap.
Correct as required or replace the fluid reservoir,
if damaged.
Check hoses: if such signs of deterioration are
detected as efficiency may be impaired, replace
them.
Metal pipes as well as connectors should not be
crushed and show no cracks; otherwise replace
parts affected.
IL
/
Fig. 289 • Side section view across wheel cylinder.
1. Rubber boots .• 2. Pistons with stems. - 3. Fluid inlet port.
4. Cylinder bOd)'. - 5. Seal rings. - 6. Spring backing washers and
piston reaction spring.
1
The edges of valve and seal rings (8 and 3)
facing respectively piston (5) and valve carrier
(4) are pushed to contact the cylinder, while the
opposite edges, which are surrounded
by
fluid
under pressure, will still have a bent shape keep-
ing them clear of cylinder also on motion.
Valve and seal ring contact area to cylinder wall
is cut to a minimum and rounded edges on the
fluid side provide effective lubrication to working
surfaces, taking friction drag to a very low rate.
This means also a distinct advantage
in
the braking
power, as brakes feel more responsive in the initial
stage when brake shoes are seating.
The by-pass port (11, fig. 288) in master cylinder
:i-""!:
is such as to allow for quick take up in case of fluid
'expansion from brake drum overheating, minimize
clogging possibilities as a result of foreign matter
entering the lines, as well as improve the line
bleeding by facilitating the expulsion of air bub-
bles from compression chamber.
Master cylinder bore: 3/4".
Fig. 290 • Sectional view of left side front wheel.
(Up to car with No. for spare 802091).
1.
Steering knuckle and arm. - 2. Brake backing plale lock washer
and nut.
~
3. Pin.
~
4. Inner cup.
~
5. Shoe guide spring.
~
6. Outer
cup. _ 7. Wheel hub.
~
8. Outer roller bearing. - 9. Hub cap.
~
10. Shoe
return spring.
~
11. Drum screw. - 12. Brake drum. - 13. Brake shoe
with lining.• 14. Brake backing plate with nul, pin and cam for shoe
clearance adjustment.
MASTER CYLINDER AND WHEEL CYLINDERS
The disassembly of master cylinder does not
involve any special difficulty.
Next to disassembly, check cylinder bore and
piston for the presence of rust, rough faces or
excessive play.
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