Page 601
When the brake pedal is released, the by-pass passage
opens immediately and the air flows from behind the
diaphragm to the front and on through the non-return
valve to the inlet manifold. The atmospheric passage
closes and the return spring returns the diaphragm, valve
piston, and push rod to the brake pedal, to the rest position. The non-return valve prevents air at atmospheric
pressure from being drawn from the inlet manifold to the
servo unit. The valve opens only when the vacuum in the
inlet manifold is greater than that in the servo cylinder.
!
t
SAMS
r
500-9
Page 603
BRAKE DISCS
CHECKING
r
The condition of the discs should be inspected when
checking the thickness of the brake pads' linings. Small
scores wil I be present on the brake discs after normal
use and should be ignored. Intermittent and irregular
braking action as a result of lateral throw or variations
in lining thickness should be rectified by grinding with
sanding blocks (refer to the separate section on this).
In more severe cases, grinding in a special machine or
replacement must be considered. Consideration must
then be given to the amount of wear of the disc, which
implies that check measurements must first be made.
Where wear is more pronounced turning in a special
machine or replacement should be considered. In such
cases measurements must be taken to determine the degree of w22.~ ori lhe disc. Corrosion and signs of wear on
the edc;e of the disc can be removed by a scraper (refer
to the section on sanding block).
Check measurements
Use a dial indicator to measure the lateral throw of the
brake disc. The maximum permissible throw is 0.004 in
(0.10 mm). Measuring of the amount of wear of the disc
can be made with the disc in position or removed from
the car. If measuring is to be carried out with the disc
fitted in the car, the brake assembly must be slackened
and any corrosion or signs of wear scraped off. Vernier
calipers and a straightedge should be used to make the
measurements. The following dimensions should be
checked.
Brake aisc with hub:
Dimension A New brake disc
Maximum after grinding
Worn brake disc
Dimension B
New brake disc
Minimum after grinding
Worn brake disc
2.075 in (52.7 mm)
2.095 in (53.2 mm)
2.102 in (53.4 mm)
2.575 in (65.4 mm)
2.555 in (64.9 mm)
2.547 in (64.7 mm)
MEASURING
THE BRAKE
DISC THROW
Brake disc removed from car:
Dimension C
Dimension D
New brake disc
Maximum after grinding
1.366 in (34.7 mm)
1.386 in (35.2 mm)
Worn brake disc
1.394 in (35.4 mm)
New brake disc
Minimum after grinding
Worn brake disc
1.866 in (47.4 mm)
1.846 in (46.9 mm)
1.838 in (46. 7 mm)
A
C
B
S6668
BRAKE
SAAB
DISC WITH HUB
BRAKE
DISC
516-1
Page 604
r
l
Dimensions for grinding and replacing of brake discs
~:.
Thickness, new brake discs
Minimum thickness, worn brake discs
Maximum wear per side (See check
measurements)
Grinding of brake discs, minimum thickness
Maximum grinding cut per side (See ·check
measurements)
0.500 in (12.7 mm)
0.44f in (11.2 mm)
0.028 in ( 0.7 mm)
0.461 in (11.7 mm)
0.020 in ( 0.5 mm)
Grinding with sanding blocks
1.
Lift the front suspension and remove the wheels.
The front suspension must be positioned horizontally in order to avoid damage to the differential
through improper lubrication.
2. Remove the brake pads and the parking brake cable.
See section 517.
3. Reset the automatic adjustment mechanism for the
handbrake by screwing back the direct-acting brake
piston.
4. · Fit a piece of No. 50 grain emery cloth to each of
the sanding blocks included in grinding kit 899691.
Clamp the emery cloth to the block by means of a
pad retaining pin, as shown in the illustration.
5. Fit the sanding.blocks with the deeper groove up and
press the hub cover onto the wheel studs.
6. Lock the wheel on· the opposite side of the car by
applying the handbrake.
7. Set the automatic adjusting mechanism for the hand, brake in. the operating position on the side of the
.. disc to be ground.
8. ·Start the engine and engage 1st gear. Use the idling
screw to adjust the idling speed. The brake djsc
should-rotate ~s slowly as possible. The grinding
" effect deteriorates at higher speeds. Cars fitted with
automatic tran·smission will require a higher rpm to
avoLd slipping in the automatic transmission.
9. Grind the disc _by pressing on the handbrake lever.
NOTE
Apply enough pressure to caus.e the brake assembly
to oscillate up afld dc;;iwn.'fhis indicates that the
thickest part of the disc is being ground. Excessive
pressure on the handQrake lever wil I reduce the
grinding effect.
.·
1O: After about 30 seconds of grinding, withdraw the
sanding blocks to clear·.them of grindings and then
return them.
11. Repeat the prOl;:eduF,euritil the osc_illating movement
of the brake assembly has ceased.
12. Fit the brake pads and reset the footbrake and handbrake (refer to section 517).
516-2
Page 605
J
..
REMOVAL
- .,
Rear bra~e discs
Front brake discs
1. Appl¥ the handbrake and remove the nut on the e_iv_ot
pin.
2. Release the brake. Remove the brake pads (see section 517).
3. Remove the two screws holding the brake housing to
the steering knuckle housing.
4. _lift the brake hose or handbrake cable. Suspend the
brake housing ·on steel wire to avoid damage to the
brake hose.
•1...01 nnect the brake hose at the brake housing.
2.·•,Remove the two screws holding the brake housing to
the rear axle.
3. Remove the· two disc retaining screws and remove the
disc.
ASSEMBLY
Lock the nut by peening it into the groove in the shaft.
Always use a new locking plate for the screws in the
brake housing. Assembly is carried out in the reverse
order. Always use a new locking plate for the screws in
the brake housing. Tighten the hub nut to the correct
torque by means of conventional spanners or wrenches
to prevent the threads being damaged.
Tightening nut with pneumatic nut tightener
If the nut is tightened using a pneuma_tic nut tightener, a
modified dished washer with an enlarged inside diameter
must be used as a special tool (see illustration).
1. Mount the modified dished washer between the hub
and the nut.
2. Tighten the nut.
3. Back off the nut and remove the modified washer._·
4. Mount the standard washer.
5. Replace the nut and tighten ·tQ the cor~ect torque.
BRAKE HOUSING SUSPENDED ON STEEL WIRE
5. Remove the brake disc from the shaft using puller
8995185 and 4 extensions 8996050 or pu lier
8996084 (later design).
(
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028·
1◄
7
~ I :~
S-5571.
•.
DISHED WASHER WITH ENLARGED
REMOVING THE BRAKE DISC
Tool 8995185 and B9960!:i0
INNER DIAMETER
oras alternative tool 8996084 (later_
design)
6. Remove the four screws holding_the brake disc to the
hub.
J'
SAM!
516-3
Page 607
BRAKE PADS
CHECKING
5. Lubricate the brake yoke's bearings by moving the
yoke backwards and forwards against the yoke spring
while the lubricant is applied on the sliding surfaces.
Because both the footbrake and handbrake are self-adjusting, it is not possible to judge by the pedal stroke or by
the lever movement whether the brake linings are worn.
It is therefore most important to remove the wheels at the
interval stated in the service program and to check the
thickness of the linings. The brake pads must be replaced
when the thickness of the lining is less than 0.080" (2.0
mm).
Gleitmo 540,
part no (45) 3008612
Brake assembly, Girling make
REMOVAL
1. Clean the brake housing.
2. Rotate the brake disc so that one of the recesses in
the edge of the disc is in line with the brake pads.
3. Remove the damper spring, pin retaining clip and Upin. If the U-pin has seized hammer 8390270 and tool
9396175 may be used to facilitate removal.
S 6672
ASSEMBLY
1. Check that the dust cover retainer is properly in position and is in good condition. Loose, damaged or split
dust covers should be replaced. If there are signs of
dirt having entered or of the pistons having corroded
nA\AI nic'ton~
·
REMOVAL OF PAD RETAINING PIN
4. Withdraw the brake pads. If the pads are seated firmly,
extractor 8995771 can be used.
REMOVAL OF BRAKE PADS WITH EXTRACTOR 8995771
.
:11nd co.oln
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pistons should never be polished.
2. To fit new brake pads the brake pistons must be pushed back in the cylinder. On the front wheel brake, this
can be done by rotating the direct piston by means of
tool 8996043 at the same time as the piston is pressed
into the cylinder.
In this way, the automatic handbrake adjustment is
reset. The same is achieved on rear wheel brakes by
pushing the direct piston into the cylinder using the
handle to tool No. 8996043. The pistons should be
pressed into the cylinders just far enougl, to allow
new pads to be fitted. A small quantity of brake fluid
will flow out of the bleeder nipple.
SCREWING THE BRAKE PISTON INTO THE f:RONT BRAKE
HOUSING WITH TOOL: 8996043
,
517-1
Page 608
CAUTION
When the brake pistons are pushed back into the
cylinder, the level in the brake fluid container will
rise. ·1fthe container is full, some of the fluid must
therefore be siphoned off before the pistons are
screwed into the cylinder housing.
CAUTION
The inner and outer brake pads have different friction properties and are not interchangeable. To avoid
confusion the pads are provided with differently shaped grooves. See illustration.
CAUTION
The piston seal can be damaged if the direct-acting
piston is recessed too far. The piston should therefore not be pressed in further than the level of the
U-pin's aperture on the brake housing.
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S 7180
BRAKE PAD MARKINGS
1. V groove in the outer brake pads.
5. Check the adjustment of the handbrake cable. Check
the distance between the handbrake lever and the yoke:
the clearance should be a maximum 0.019 in. (0.50
mm) and should be equal on both sides. Adjust as necessary using the adjustment nut on the handbrake
lever.
S 6669
THE BRAKE PISTON IS PRESSED INTO THE REAR BRAKE
HOUSING TOOL 8996043
3. Check that the position of the pistons has not moved
the dust cover. At the same time, check that the yoke
moves easily in the groove on the brake housing. Remove any rust or worn edges from the periphery of
the disc.
4. Fit the new brake pads together with the U-pin, pin
retaining clip and damper spring.
WB
Note that the cables cross over, therefore. the righthand adjustment nut should be used to adjust the
left-hand brake mechanism and vice versa.
6. With the engine switched off, pump the brake pedal
repeatedly until the footbrake starts to operate.
7. Pull the handbrake lever up five notches. Continue
to pump the brake pedal until the handbrake operates
after having been pulled up a further two-four notches.
Page 609
CAUTION
The car must not be driven before both the footbrake and the handbrake are functioning properly.
REMOVAL OF BRAKE PADS WITH EXTRACTOR
"""
HANDBRAKE
8995771
ASSEMBLY
LEVER
1. Check that the dust cover retainer is properly in position and that the cover is in good condition. Loose,
damaged or split covers should be replaced. If there
are signs of dirt having•entered or of pistons having
corroded new pistons and seals should be used. Corroded pistons should never be polished.
2. To fit new brake pads, the brake pistons .nust be
pushed back into the cylinder. The pistons should be
pressed into the cylinder far enough to allow new
pads to be fitted without binding. Use the shaft of
tool 8996043.
1. Neutral position
2. Adjustment position (5 notches)
3. Full brake efficiency (7-9 notches)
Brake assembly, ATE make
REMOVAL
1. Clean the brake housing.
2. Rotate the brake disc so that one of the recesses in
the edge of the disc is in line with the brake pad.
3. Remove the cover plate, the locking pins and spring
which retain the brake pads.
4. Removethe brake pads.For pads which haveseized,
useextractor No. 8995771.
SAAB
CAUTION
When the brake pistons are pushed back into the
cylinder, the level in the brake fluid container will
rise. If the container is full, some of the fluid must
therefore be siphoned off before the pistons are
screwed into the cylinder housing.
.--r,,
517-3
Page 610
3. Fit the spring, locking pins and cover plate. Repeat
the same procedure on the opposite wheel and then
top up the brake fluid container as necessary.
CAUTION
Before the car can be driven, the brake pads must be
brought out to the brake disc. This is achieved by
repeated pumping of the brake pedal with the engine
switched off until the foot brake and hand brake are
functioning properly.
Refrain from depressing the pedal after the hand
brake has started to operate, as this will cause overadjustment of the hand brake mechanism and may
cause the brakes to seize.
SAAB