Page 611
HYDRAULIC FOOTBRAKE SYSTEM
INSTRUCTION FOR OVERHAUL
Scrupulous cleanliness is essential when the brake
system or any part of it is dismantled. Clean any dismantled parts in brake fluid or in a special cleaning
solution for hydraulic brake components. Wipe the
parts with a clean, lint-free cloth. All rubber parts
and seals, etc., are available in repair kits and should
be replaced. Before a unit is installed, all component
parts should be dipped in clean brake fluid of the recommended specification.
3. Pump the brake pedal repeatedly.
4. Connect a hose to the bleeder nipple at the left rear
wheel. Place the free end of the hose in a container
part filled with brake fluid. The end of the hose must
be kept below the surface of the liquid in the container
at all times. Open the bleeder screw one to two turns.
CHANGING BRAKE FLUID
All brake fluids deteriorate with time through oxidation
and water absorption. The boiling point is lowered and a
build-up of vapour is possible after repeated hard braking
and this may result in brake failure. The brake fluid
should therefore be replaced at regular intervals. If the
car is used for normal driving this should be every other
year or every 25,000-30,000 miles (40,000-45,000 km).
If the car is used for competition or alpine driving, the
fluid should be changed every year.
1. Open the bleeder nipples for the secondary circuit
(right front wheel-left rear wheel) one turn and connect suitable hoses to them placing the other ends in
a container.
2. Pump the brake pedal until the front half of the fluid
reservoir is nearly empty.
3. Top up with new fluid and continue pumping until
the reservoir is nearly empty.
4. Top up the reservoir once again and close the bleeder
nipples.
5. Repeat the same procedure for the primary circuit.
6. Bleed the brake system.
BLEEDING THE LEFT REAR WHEEL
BLEEDING
5. Fully depress the brake pedal, and then release it
after a pause of a few seconds. Wait a few seconds
then repeat the procedure. Continue in this way until
all air bubbles have been expelled from the hose.
Tighten the nipple immediately after the last forward
stroke.
6. Repeat the procedure described in points 4 and 5 with ·
the right front wheel. Then change to the primary circuit by bleeding first the right rear wheel and then the
left front wheel.
If air has entered the system, this can be detected by
sponginess in the brake pedal, the need to press the pedal
several times before the brake grips or by a lack of resistance. Checking by depressing the pedal should be carried
out with the engtne switched off and with no assistance
from the servo uriit. If small quantities of air are present
in one of the circuits, this may result in uneven braking
of the car but without sponginess in the brake pedal.
Bleeding must be carried out after any component in the
system has been removed. It is usually sufficient to bleed
the brake housing or the circuit in which work has been
carried out. A bleeder nipple is fitted to each brake housing. The best and fastest results are achieved with bleeding
equipment, in which case the manufacturer's instructions
should be followed.
1. Place chocks under the wheels and release the handbrake.
2. Make sure that the brake fluid reservoir is well filled
and that the vent holes in the cap are not blocked.
BLEEDING OF FRONT WHEEL
Aug. 1975
520-1
Page 612
7. Top up the fluid reservoir.
Up to and incl. 1977 model:
During bleeding, the brake warning lamp will light up as
a result of uneven pressure in the system. However, the
lamp will go out as soon as the piston in the brake valve
of the master cylinder returns to its central position, i.e.
as soon as the brakes are used after bleeding has been
completed.
CAUTION
New clean brake fluid of the recommended specification should always be used for topping up the
brake fluid reservoir.
The brake fluid which has been pumped out during
bleeding should never be reused.
520-2
S.1"9
.l
Page 613
MASTER CYLINDER
INSTRUCTIONS FOR OVERHAUL
Scrupulous cleanliness is essential when the brake
system or any part of it is dismantled. Clean any dismantled parts in brake fluid or in a special cleaning
solution for hydraulic brake components. Wipe the
parts with a clean, lint-free cloth. All rubber parts
and seals, etc., are available in repair kits and should
be replaced. Before a unit is installed, all component
parts should be dipped in clean brake fluid of the recommended specification.
REMOVING THE STOP PIN ON THE SECONDARY PISTON
REMOVAL
1. Lay a suitable protective material over the front fender and place rags under the master cylinder to avoid
damage to the paintwork in case the brake fluid should
be spilt.
2. Disconnect the electric connection to the brake warning switch.
3. Disconnect the hose from the clutch master cylinder
to the fluid reservoir. Insert a plastic stopper in the
nipple of the reservoir.
4. Disconnect the two brake line connections to the master cylinder.
5. Remove the two nuts which hold the master cylinder
to tt,e servo unit and remove the master cylinder.
5. Remove the circlip on the primary piston and take out
the primary piston together with the spring and the
seals.
DISMANTLING
REMOVING THE CIRCLIP ON THE PRIMARY PISTON
1. Empty the brake fluid reservoir and mount the master cylinder in a vice.
2. Remove the pins securing the container to the cylinder
body. As from model 1978, drive out the pins by
means of a drift.
3. Remove the reservoir and by means of a small screwdriver remove the rubber seals from the hole for the
fluid reservoir.
4. Push the primary piston into the master cylinder and
pull up the stop pin on the secondary piston.
6. Remove the cylinder housing from the vice and knock
it carefully against a wooden surface so that the secondary piston falls out. Alternatively, the secondary piston can be forced out with compressed air.
7. Remove the springs and seal rings from the two pistons.
Keep the pistons and their rings apart so that they can
be fitted back into the cylinders from which they have
been removed.
CAUTION
Never attempt to extract the seals with sharp-edged
tools which may scratch the pistons. If necessary,
use a small screwdriver with smoothly rounded
edges.
521-1
Page 614
14
13
S 4322
4
MASTER CYLINDER,
EXPLODED VIEW, MODEL 1975-1977
1. Fluid reservoir
2. Pin
3. Pin retaining clip
4. Connection
5. Brake warning piston
6. Cylinder housing
7. Stop pin (secondary piston)
8. Brake warning switch
9. Sealing ring
10. Return spring (secondary piston)
11. Secondary piston
12. Return spring (primary piston)
13. Primary piston
14. Lock ring
1415
9
MASTER CYLINDER,
1. Cap
2. Fluid level contact
3. Float
4. Sealing ring
5. Brake fluid container
6. Pin
7. Sealing ring
8. Stop pin
521-2
10
11
12
EXPLODED VIEW, AS FROM MODEL 1978
9. Cylinder housing
10. Spring, secondary piston
11. Secondary piston
12. Sleeve
13. Spring, primary piston
14. Primary piston
15. Lock ring
S 6152
Page 615
Brake warning valve, model 1975-1977
8.
With the cylinder housing still in the vice remove
the switch assembly.
Remove the screws in the front part of the cylinder
housing.
Remove the cylinder housing and knock it gently
against a wooden surface so that the valve piston
and sleeve fall out.
Remove the inner 0-ring by means of a bent piece
of steel wire. Take care not to damage the surface
of the cylinder.
9.
10.
11.
2
3
4
5
S6153
SECONDARY PISTON WITH SEALS, MODEL 1975-1977
1. Spring seat
2. Piston seal
3. Washer
4. Primary piston
5. Piston seal
3. Fit new seals to the primary piston in the same way.
3
5
1
BRAKE WARNING VALVE, EXPLODED VIEW
1. End plug
2. Copper gasket
3. O-ring
4. Sleeves
5. Circlip
6. Brake warning switch assembly
7. Valve piston
ASSEMBLY
3
4
5
S4325
PRIMARY PISTON WITH SEALS, MODEL 1975-1977
1. Spring seat
2. Piston seal
3. Washer
4. Primary piston
5. Piston seal
1. After cleaning, check that the cylinder bore and pistons are free from scratches and corrosion. Worn or
damaged parts should be replaced.
2. Fit new piston seals to the secondary piston. This is
made easier if the piston and seals are first dipped in
brake fluid. Check that the seals are turned the correct
NOTE!
Up to and incl. chassis No. 99752040987 was an
intermediate piston seal mounted on the secondary piston. This seal is no longer mounted and
should not be installed in master cylinder in connection with overhaul.
2
3
4
5
SECONDARY PISTON WITH SEALS, AS FROM MODEL 1978
1. Spring seat
2. Piston seal ,,
3. Washer
4. Piston
5. Piston seal
521-3
Page 616
1
2
3
4
5
s 7086
PRIMARY PISTON WITH SEALS, AS FROM MODEL 1978
1. Spring seat
2. Piston seal
3. Washer
THE GROOVE IN THE VALVE PISTON
4. Primary piston
5. Piston seal
4. Mount the master cylinder in a vice, thoroughly lubricate the cylinder bore and carefully insert the complete
secondary piston with the spring. Great care must be
taken to avoid damage to the piston seals. Push in the
secondary piston by means of a clean screwdriver and
insert the stop pin.
5. Insert the complete primary piston in the same way
and fit the circlip.
Brake warning valve, model 1975-1977
6. Fit new circlips to the valve piston. Fit the sleeves and
new O-rings.
7. Lubricate the piston thoroughly with brake fluid and
insert it in the cylinder. The groove for the brake warning switch should be in line with the contact connections.
8. Screw in the brake warning switch.
9. Fit a new copper gasket and screw in the end plug.
FITTING
1. Screw the master cylinder to the servo unit.
2. Connect the brake line connections, the hose from
the clutch master cylinder and the electrical connection for the brake warning switch.
3. Bleed the brake system.
Level warning system, as from model 1978
Check the level warning system by using a finger to depress the switch in the fluid container cover.
INSERTING THE VALVE PISTON IN THE CYLINDER
CHECKING THE LEVEL WARNING SYSTEM
521-4_
!
Page 617
BRAKE LINES
CHECKING
For reasons of safety, all pipes, rubber hoses, connections,
etc., in the brake line system must always be kept in first
class condition. It is therefore essential that these parts
are checked regularly in conjunction with the service program. Brake pipes fitted to the body by means of clips
must not be corroded or fitted in such a way that they
can chafe against other parts; nor should there be any
visible signs of damage. All hoses and connections should
be tightened securely without any leaks. Damaged parts
should be replaced.
REMOVAL
1. Clean all connections to the damaged pipe.
2. Unscrew the connecting nuts on the pipe together with
any clips.
3. Insert plastic stoppers in the open ends and then remove the damaged pipe.
FITTING
1. Clean a new brake pipe internally by blowing clean,
moisture-free compressed air through it.
2. Position the pipe, remove the plastic stoppers and
tighten the connecting nuts.
3. Bleed the brake system.
CAUTION
When fitting brake hoses, it is highly important to
position them correctly, thereby ensuring that steering or suspension movements do not bring them into
contact with other parts of the car. The brake hoses
must not be twisted. The front brake hoses must be
fitted with the wheels hanging free and should be
pointed straight ahead. The brake pipes must not be
bent or twisted after they have been secured.
SA_1'B
522-1
Page 619
WHEEL CYLINDERS AND
BRAKE HOUSINGS
,,.
Removal
1. Remove the brake pads. See Section 517.
2. Disconnect the handbrake cable from the brake housing.
INSTRUCTIONS FOR OVERHAUL
Scrupulous cleanliness is essential when the brake
system or any part of it is dismantled. Clean any
dismantled parts in brake fluid or in a special cleaning solution for hydraulic brake components. Wipe
the parts with a clean, lint-free cloth. All rubber
parts and seals, etc., are available in repair kits and
should be replaced. Before a unit is installed, all
component parts should be dipped in clean brake
fluid of the recommended specification.
.....---
FRONT BRAKE HOUSING
REMOVING THE CIRCLIP FROM THE HANDBRAKE CABLE
Lubrication
The sliding surfaces between the yoke and the brake housing should be lubricated in accordance with the service
inspection programme and whenever work is carried out
o.n the front brake assemblies. Lubrication can be carried
out without removing the assemblies of brake pads.
1. Scrape away any dirt around the sliding surfaces of
the yoke on the brake housing.
2. Apply drops of Gleitmo 540, Part No. (45) 3008612,
to the sliding surfaces, sliding the yoke back and forth
simultaneously.
3. Unscrew the brake pipes to the brake housing at the
hose connection. (See illustration). Insert a rubber
stopper in the connection to avoid spillage from the
pipe.
DISCONNECTING THE BRAKE PIPE
4. Remove the two screws which hold the brake housing
to the steering knuckle housing.
Dismantling
1. Clean the brake housing and mount it in a vice.
2. Remove the return spring on the handbrake lever.
3. Remove the yoke from the brake housing and remove
,,
the spring and the handbrake lever.
·
SAAB
523-1
- J
Page 620
FORCING OUT THE INDIRECT PISTON WITH COMPRESSED
AIR
REMOVING THE YOKE
4. Remove the dust cover retaining ring and the dust
cover.
5. Force out the indirect piston by means of compressed
air.
6. Pressthe push rod by hand so that the direct piston is
separated from the cylinder.
..
7. Remove the O-rings and seal rings from the piston and
from the cylinder bore. The O-ring retainer in the handbrake lever should only be removed if it is damaged.
17
NOTE
The indirect piston and internijl parts comprise a
complete unit and must not be rinsed in brake fluid
or any other cleaning fluid but sh(?uld only be wiped
clean; the lubricating grease for the handbrake mecha
nism will otherwise be washed off.
2
S 5182
FRONT BRAKE HOUSING, EXPLODED VIEW
1. Dust cover holder
2. Dust cover
3. Piston (directl
4. Push rod
5. Brake housing
6. Piston seal
7. Guide clip
523-2
15. Pad retaining pin
16. Lock clip
17. Brake pads
18. Spring
19. Damper spring
20. RetainPr (two O-rings)
8. Bleeder nipple
9. O-ring
10. Piston (indirectl
11. Spring (left-green, right-red)
12. Spring (handbrake lever)
13. Handbrake lever
14. Yoke
SUB