Page 441
Brake Fluid and Brake Bleeding
520-1
520 Brake Fluid and Brake Bleeding
General
520-1
To bleed brake system (cars with ABS)
Bleeding and Changing Brake Fluid .. 520-1
520-1
Bleeding the Brake System
To bleed brake system (cars without ABS). . . 520-1
GENERAL
Brake fluid has the job of transmitting the force applied at
the pedal to the brake pads. In order for the fluid to properly
transmit the force, it must be "free of air and moisture. Because
of the moisture-absorbing properties of brake fluid, it is essential that the fluid be replaced on a regular basis to prevent corrosion of brake parts and brake system failure. See 110
Maintenance Program for the specified intervals for changing brake fluid.
BLEEDING AND CHANGING BRAKE
FLUID
Bleeding is the process used to purge air bubbles or flush
contaminated fluid from the system. Bleeding brakes periodically is good preventative maintenance, but it is also essential
any time the system has been opened, such as when disconnecting a brake line. A spongy feeling brake pedal is a sign
that brakes may need to be bled.
Bleeding the brake system can be done using pressure
bleeding equipment, vacuum bleeding equipment, or by conventional means using two people.
WARNING
• Brake fluid is poisonous. Wear safety glasses when working
with brake fluid. Wear rubber gloves to prevent brake fluid
from entering the bloodstream through cuts of scratches. Do
not siphon brake fluid with your mouth.
• Brake fluid is considered a hazardous waste. Catch brake
fluid in a suitable container. Dispose of brake fluid in a manner
that is mindful of the environment and meets ordinances goveming disposal of wastes.
• On cars equipped with ABS, the ABS system is self-pressurizing and maintains very high hydraulic pressure, as much as
210 bar (3045 psi). Before working on any part of the ABS system, switch off the ignition and disconnect the cable from the
battery negative (-) terminal.
520-2
TABLES
a. Order for Bleeding Brakes
(Cars without ABS)
520-1
NOTE
It is good practice to flush the clutch hydraulic system whenever the brake fluid is being changed. See 412 Clutch Control to bleed the clutch hydraulic system.
Bleeding the Brake System
The procedure below is for bleeding the brakes using a
manual method and requires a helper. When using other
methods-such as vacuum or pressure bleeding equipment,
follow the instructions given by the equipment's manufacturer.
CAUTION
Use only DOT 4 brake fluid. Do not use silicone based
(DOT 5) brake fluid.
To bleed brake system (cars without ABS)
Bleeding the brakes or replacing the brake fluid must be
done in a particular order as shown in Table a.
CAUTION
Brake fluid absorbs moisture from the air. Add only unused fluid to the system and only from well-sealed or previously unopened containers. Do not use fluid expelled from the system,
even if it is fresh fluid.
Table a. Order for Bleeding Brakes
(Cars without ASS)
1985-1987 models
1988-1989 models
1. Right front wheel
1. Left rear wheel
2. Left rear wheel
2. Right front wheel
3. Left front wheel
3. Right rear wheel
4. Right rear wheel
4. Left front wheel
1. Check the level of the brake fluid in the master cylinder
reservoir. If only bleeding the brakes, top up the reservoir using fresh brake fluid from a sealed container.
GENERAL
Page 442
520-2
Brake Fluid and Brake Bleeding
• Brake fluid -
DOT 4
NOTE
• When replacing the brake fluid, remove as much of the old
fluid from the reservoir as possible, then fill the reservoir with
new brake fluid. Plan to have approximately 1.2 liters of new
fluid on hand to flush the system.
if
~1llJIIJ
..
• Brake fluid is very harmful, especially to paint and rubber
parts. Spilled brake fluid should be cleaned up immediately.
II
I
2. Starting at the first caliper listed in Table a, place a hex
~~-_V
wrench over the caliper bleeder. Then connect a length
of clear tubing to the bleeder. Place the other end of the
tube in a container. See Fig. 1.
87938-85/460
Fig. 2.
Front caliper bleeder (arrow).
5. Repeat the above from procedure (step 1 through step
4) bleeding the next caliper in the order given above in
Table a.
To bleed brake system (cars with ASS)
On cars with ABS the front brakes must be bled first. The
front brakes can be bled using pressure bleeding equipment
or they can be bled manually. The rear brakes are bled using
the ABS pump as described below.
Fig. 1. Tube and container to bleed brake caliper. Arrow shows
wrench on bleeder.
1. Bleed the front brakes using the technique described
above. Bleed the right front caliper then the left front
caliper.
NOTE
NOTE
The bleeder is a small hex-head fitting with a hollow center
and usually has a rubber dust boot over it. See Fig. 2.
3. Have a helper pump the brake pedal slowly three times
and hold it down.
• When replacing the brake fluid, remove as much of the old
fluid from the reservoir as possible, then fill the reservoir with
new brake fluid.
• When replacing the brake fluid, remove at least 1 pint (500
cc) of brake fluid from each caliper to completely expel the old
fluid.
4. Open (unscrew) the bleeder about 1/2 turn. As the ped
2. Bleed the rear calipers by connecting a length of clear
al goes to the floor and the fluid stops flowing, close the
bleeder. Release the pedal and repeat step 3 until the
pedal feels hard or all of the air has been expelled from
the system.
tubing to the bleeder and placing the other end in a
container. See Fig. 3.
3. Have a helper turn the ignition key to run (engine off)
then press the brake pedal. The ABS pump will come
on.
NOTE
When replacing the brake fluid, remove at least 1 pint (500
cc) of brake fluid from each caliper to completely expel the
old fluid.
BLEEDING AND CHANGING BRAKE FLUID
4. Working at the caliper, loosen (unscrew) the bleeder
about 1/2 turn and let the fluid flow until it is 'free o'f bubbles. Close the bleeder.
Page 443
Brake Fluid and Brake Bleeding
520-3
5. Check the level of the fluid in the reservoir. If necessary, repeat steps 2 through 4 at the other rear caliper.
CAUTION
• Do not allow the ASS pump to run more than 2 minutes or it
may overheat. After running 2 minutes, allow the pump to cool
for 10 minutes.
• Do not allow the ASS pump to run without fluid. Damage to
the pump may result.
Top up the brake fluid in the reservoir as necessary and replace any dust caps.
Fig. 3.
Rear caliper being bled on model with ABS,
BLEEDING AND CHANGING BRAKE FLUID
Page 444
Brake Master Cylinder
521-1
521 Brake Master Cylinder
Master Cylinder and Fluid Reservoir. 521-1
To remove master cylinder
521-2
To remove ASS unit.
To install ASS unit
521-3
521-5
On cars with ABS, the master cylinder has three brake circuits: Individual circurts for each front wheel and one circuit for
the rear wheels. The master cylinder is integrated with other
ABS components to form the ABS unit. See Fig. 2.
MASTER CYLINDER AND FLUID
RESERVOIR
The master cylinder, on cars without ABS, has two chambers that create pressure in two hydraulic circuits. One chamber controls the right front and left rear brakes. The second
chamber controls the left front and right rear brakes. This design-known as dual diagonal braking-assures a high level
of braking control if one circuit fails. Fig. 1 shows an exploded
view of the master cylinder used on cars without ABS.
The master cylinder has an integral brake fluid reservoir.
The fluid reservoir has chambers forthe brake master cylinder
and for the clutch master cylinder (where applicable). The reservoir cap has a float switch that signals the driver when the
fluid level is low.
CAUTION
Whenever the brake system is open, plug all openings to prevent dirt from entering the system. Even a minute particle of
dirt can cause problems.
Rg. 2. ABS braking unit with integral master cylinder.
1
2
3
.
.:
Reservoir cap
Fluid level switch
Float
Seal ring
Reservoir
6. Pins to secure reservoir
7. Sealing rings
8. Stop pin
1.
2.
3.
4.
5.
9. Cylinder housing
10. Spring
11. Piston
12. Sleeve
13. Spring
14. Piston
15. Lock ring
12
11
B7940-S6152
Rg. 1. Exploded view of brake master cylinder.
MASTER CYLINDER AND FLUID RESERVOIR
ill
:;~;
Page 445
521-2
Brake Master Cylinder
The master cylinder displaces brake fluid when the brake
pedal is depressed. The displaced fluid moves a piston in
each caliper, which in turn presses the brake pads against the
rotor. The master cylinder must displace fluid without losing
pressure or leaking. When it cannot do this, it must be replaced. If there is any leakage from around the master cylinder the master cylinder is probably faulty and should be
replaced. For troubleshooting information see 500 Brakes
General.
NOTE
• Unexplained fluid loss from the reservoir could be due to
brake fluid leaking from the master cylinder into the vacuum
booster. The fluid is drawn into the engine through the vacuum booster hose. Look for seepage at the master cylinder to
vacuum booster flange. Replace both the master cylinder and
the vacuum booster as the diaphragm in the booster may be
damaged.
• Check the master cylinder by holding the pedal down hard
with the car stopped and the engine running. The pedal
should feel solid and stay solid. If the pedal slowly falls to the
floor, either the master cylinder is leaking internally, or fluid is
escaping from the system. If no leaks can be found, the master cylinder is faulty and should be replaced.
Fig. 4. Special clamping pliers (arrow) used to pinch off supply
line to clutch master cylinder.
WARNING
• Brake fluid is poisonous. Wear eye and hand protection
when working with brake fluid.
• Brake fluid is considered a hazardous waste. Recycle or dispose of brake fluid in a manner that is mindful of the environment and meets ordinances governing disposal of wastes.
To remove master cylinder
1. Disconnect the electrical wires from the fluid reservoir
cap.
2. Remove the vacuum hose with check valve from the
vacuum booster. See Fig. 3.
CAUTION
Brake fluid is very harmful, especially to paint and rubber
parts. Spilled brake fluid should be cleaned up immediately.
5. Using a brake line (flare) wrench, loosen the brake line
fittings and remove the two brake lines from the master
cylinder. See Fig. 5.
NOTE
To make access to the brake lines easier, remove the mounting bolt holding the coolant expansion tank and move the tank
out of the way. It is not necessary to drain the coolant.
Fig. 3. Vacuum hose and check valve (arrow) removed from vacuum
6. Remove the two nuts holding the master cylinder to the
vacuum booster. Remove the master cylinder.
booster.
3. Using a syringe, remove as much brake fluid from the
reservoir as possible.
4. On cars with manual transmission, pinch off the fluid
supply hose to the clutch master cylinder. See Fig. 4.
Remove the supply hose and plug the fittings.
MASTER CYLINDER AND FLUID RESERVOIR
Installation is the reverse of removal. Inspect the seal between the master cylinder and the vacuum booster and replace
if necessary. A faulty seal can be the source of a vacuum leak,
causing a reduction in braking performance and/or an erratic
idle speed. Bleed the brakes as described in 520 Brake Fluid
and Brake Bleeding using DOT 4 brake fluid from a sealed
container.
Page 446
Brake Master Cylinder
521-3
2. Remove the lower dashboard pad and footwell heating
duct as described in 851 Interior Trim and Upholstery.
3. Working at the brake pedal assembly, remove the padded insulating material. Then remove the defroster
hose from the heater box.
4. Remove the brake pedal pushrod pin locking clip and
the push rod pin from the ASS unit. See Fig. 6.
CAUTION
Inspect the pushrod locking clip and clevis pin and replace
them with new ones if they are in anyway damaged or deformed.
Fig. 5.
Brake line being removed. Coolant tank (arrow) has been
moved out of way.
CAUTION
Always start the brake line fittings by hand to prevent stripping
the threads.
NOTE
It is good practice to flush the clutch hydraulic system whenever the brake fluid is being changed or the master cylinder is
being replaced. See 412 Clutch Control for details on bleeding the clutch hydraulic system.
To remove ASS unit
The ASS unit is removed from the car as a complete assembly. Certain replacement parts for the ASS unit are available
from an authorized Saab dealer. See your dealer for the latest
parts information.
Fig. 6. Brake pedal pushrod locking clip (arrow). Note the orientation of the pin and locking clip.
5. Working at the front of the engine compartment, remove the air intake duct. See Fig. 7.
WARNING
• Dangerously high pressure may be retained in the ABS system, even though the car is not running or has not been driven
recently. Never attempt to open or disassemble the pressure
accumulator, which contains a nitrogen gas charge and is under high pressure.
• If the ANTI-LOCK and the BRAKE FLUID warning lamps
should come on, the car must not be driven. Brake failure may
occur. Have the problem corrected promptly by an authorized
Saab dealer.
1. Depressurize the ASS system before loosening any
components by disconnecting the battery negative cable and pressing the brake pedal 25 to 30 times, or until
there is a noticeable increase in pedal effort.
Fig. 7. Air intake duct being removed.
MASTER CYLINDER AND FLUID RESERVOIR
Page 447
521-4
Brake Master Cylinder
6. Remove the coolant expansion tank to body mounting
bolt and move the tank aside. See Fig. 8. Do not disconnect any cooling hoses or remove the cap from the
tank.
Fig. 10. ABS unit mounting bracket being removed,
Fig. 8. Coolant expansion tank being moved out of way,
7. Disconnect all electrical connectors from the ABS unit.
Remove the ground lead. See Fig. 9.
WARNING
• Brake fluid is poisonous. Wear eye and hand protection
when working with brake fluid.
• Brake fluid is considered a hazardous waste, Recycle ordispose of brake fluid in a manner that is mindful of the environment and meets ordinances governing disposal of wastes.
CAUTION
Brake fluid is very harmful, especially to paint and rubber
parts, Spilled brake fluid should be cleaned up immediately,
10. On cars with manual transmission pinch off the supply
hose to the clutch master cylinder. Remove the hose
from the reservoir. See Fig. 11.
1. Pressure switch
2. Main valve
3, Brake fluid level indicator
switch
4, ABS pump motor
Fig. 9. ASS unit electrical connectors, Arrow shows ground lead,
8. Remove the ABS unit mounting bracket. See Fig. 10.
9. Using a syringe, siphon off the brake fluid from the reservoir.
Fig. 11. Supply hose to clutch master cylinder being removed,
Brake lines can be seen below hose fitting,
11. Label and remove the brake lines from the ABS unit using a brake line (flare) wrench.
MASTER CYLINDER AND FLUID RESERVOIR
"
Page 448
Brake Master Cylinder
NOTE
Plug or cover the brake lines and the openings in the ASS unit
to prevent dirt from entering system.
521-5
2. Working in the passenger compartment, install the pedal push rod pin and locking clip through the ABS unit
push rod. See Fig. 6 above.
3. Install and tighten the four new nuts that hold the ABS
unit to the bulkhead. See Fig. 12 above.
12. Working in the passenger compartment above the pedals, remove the four nuts that hold the ABS unit to the
bulkhead. See Fig. 12.
WARNING
Always use new self-locking nuts to moun! the ASS unit to the
bulkhead.
Tightening torque
• ABS unit to bulkhead
26±4 Nm (19±3 ft-Ib)
4. Connect the brake lines to the ABS unit. See Fig. 11
above.
CAUTION
Always start the brake line fittings by hand to prevent stripping
the threads.
Fig. 12. ASS unit mounting nuts (arrows). Nuts are ac
cessible in passenger compartment above
pedal assembly,
To install ASS unit
1. Carefully install the ABS unit in the opening in the bulkhead. Position the ABS unit pushrod so it correctly
aligns with the brake pedal.
The remainder of installation is the reverse of removal. Fill
the reservoir with DOT 4 brake fluid from a sealed container.
Switch on the ignition and check that the ABS pump comes
on. Bleed the system, including the clutch, as described in 520
Brake Fluid and Brake Bleeding and 412 Clutch Control.
Check that there are no leaks and that the warning lights go
out after the car is started. Finally, test drive the car to check
all brake functions. Recheck the brake fluid level.
CAUTION
Use care when installing the ASS unit through the bulkhead.
The brake light switch and cruise control switches on the pedal assembly can be easily damaged.
MASTER CYLINDER AND FLUID RESERVOIR
Page 449
Brake Lines
522-1
522 Brake Lines
Brake Lines and Hoses
To replace brake lines or brake hoses
522-1
522-1
BRAKE LINES AND HOSES
The brake lines carry brake fluid and transmit hydraulic
pressure to the calipers at each wheel. They are rigid up to
their connecting points with the flexible hoses near the
wheels. The flexible hoses are used to accommodate suspension and steering movement. Normally, no maintenance is required other than inspecting the lines and hoses for leaks or
deterioration. Fig. 1 shows the typical brake line and hose
routing.
Brake lines are available from Saab pre-formed to fit without any bending or modification. See an authorized Saab
dealer for the latest parts information.
WARNING
• On cars equipped with ABS, dangerously high pressure may
be retained in the ABS system even though the car is not running or has not been driven recently. Before loosening any
brake line fitting, depressurize the system by disconnecting
the battery negative cable and pressing the brake pedal 25 to
30 times, or until there is a noticeable increase in pedal effort.
WARNING
Brake fluid is considered a hazardous waste. Catch brake fluid in a suitable container and label it. Recycle or dispose of
brake fluid in a manner that is mindful of the environment and
meets ordinances governing disposal of wastes.
To replace brake lines or brake hoses
1. Clean the connections of the brake line at both ends.
2. Remove any brake line clamps or tie-downs. Loosen
the fittings using a brake line (flare) wrench.
NOTE
Brake lines to the rear brakes travel under the carpeting in the
passenger compartment on the driver side. See 8 BODY for
information on removing the seats, Sill plates, and carpeting.
3. Remove the brake line or hose.
• Brake fluid is poisonous. Wear hand and eye protection.
87969·SG768
Rg. 1. Brake lines and hoses. Also shown is parking brake with cables.
BRAKE LINES AND HOSES
Page 450
522-2
Brake Lines
CAUTION
• Brake fluid is harmful to paint and rubber parts. Spilled brake
fluid should be cleaned up immediately.
• Plug the openings in the hydraulic system to prevent dirt
from entering the system. Even a minute particle of dirt can
cause problems.
4. Clean the inside of the new brake line or hose with
compressed air.
5. Place the line or hose in position and hand tighten the
fittings. When connecting lines to hoses, counter hold
the fittings using two wrenches during tightening.
CAUTION
• Always start the brake line fittings by hand to prevent stripping the threads.
• When fitting flexible hoses, be sure the hose is not twisted
and is properly positioned. Check that the hose does not contact any suspension or steering parts.
BRAKE LINES AND HOSES
NOTE
When replacing front flexible brake hoses, jack the car up and
support it so the road wheels are freely suspended and pointing straight ahead. This will ensure that there is the proper
amount of slack in the hose when the car is jacked up.
6. Tighten the brake fittings using a brake line wrench,
and, if necessary, reinstall any clamps or tie-downs.
CAUTION
Never attempt to bend or twist brake lines after the fittings
have been tightened. If any lines are at all kinked they must
be replaced.
The rest of installation is the reverse of removal. Fill the reservoir with DOT 4 brake fluid from a sealed container. Bleed
the system as described in 520 Brake Fluid and Brake
Bleeding. Check that there are no leaks. Finally test drive the
car to check all brake functions. Recheck the brake fluid level.