1973 OPEL GT-R brakes

5B- 141973 OPEL SERVICE MANUALConditionPossible CauseCorrection2. Partial system failure.2. Check front and rear brake system
and repair, if necessary. Also, check
brake warning light, if a failed
system is found and light did not
function.
3. Excessively worn shoe
and lining.3. Check and replace in axle sets.
4. Piston in caliper stuck
or sluggish.4. Remove caliper and rebuild.
5. Fading brakes due to
incorrect lining.
6. Vacuum leak.5. Remove and replace with original
equipment lining.
6. Check for ruptured hose or loose
attachment.
Excessive Pedal Travel1. Partial brake system
failure.1. Check both front and rear system
for a failure and repair. Also, check
warning light
- it should have indi-
cated a failure.
2. Insufficient fluid in
master cylinder.
3. Poor rear brake
adjustment.2. Fill reservoirs with approved
brake fluid. Check for leaks.
3. Adjust rear brake per
specifications.
4. Air trapped in system.4. Bleed system.
5. Bent shoe and lining.5. Replace axle set of shoe and
lining.
Dragging Brakes (A very
light drag is present in
all disc brakes
immediately after pedal
is released.)1. Master cylinder pistons
not returning correctly.1. With reservoir cover off, check
for fluid spurt at bypass holes as
pedal is depressed. Adjust push rod,
if necessary, or rebuild master
cylinder.
2. Restricted brake tubes2. Check for soft hoses or damaged
or hoses.tubes and replace with new hoses and
new double-walled steel brake tubing.
3. Incorrect parking brake
adjustment on rear brakes.3. Check and readjust to correct
specifications.
Grabbing or Uneven Braking
Action (All conditions
listed under “Pulls”
.)4. Check valve installed in
outlet to front disc brakes.
1. Malfunction of power
brake unit.4. Check master cylinder outlet and
remove check valve if present.
1. Check operation and repair, if
necessary.

DISC BRAKES5B- 15
ConditionPossible Cause
2. Binding brake pedal
mechanism.Correction
2. Check and lubricate, ifnecessary.3. Corroded caliper
assembly.3. Clean and lubricate.
MAINTENANCE AND ADJUSTMENTSDISC BRAKE MAINTENANCE
Checking Brake Fluid Level
The brake fluid level in the brake fluid container
must be checked during predelivery inspection, then
every 3,000 miles during inspection and preventive
maintenance servicing.
The brake fluid level must not be higher than the
inscription “MAX” and must be at least up to
“MIN”. Replenish brake fluid, if necessary.
Because of the relatively large brake caliper bore
cross section and the self-adjustment of the disc
brakes, resulting in a greater piston travel to compen-
sate for friction pad wear, the brake fluid level drops
faster than in fluid containers for drum brakes with
their smaller wheel brake cylinders. For this reason
pay special attention to the fluid level in the brake
fluid container.
Drop of brake fluid level can be due to friction pad
wear and may not be due to leakage in the braking
system.On loss of brake fluid due to leakage, the brake sys-
tem must be checked thoroughly.
Friction Pad Adjustment
Friction pad adjustment is not necessary on the front
wheel disc brakes as this is done automatically by the
pistons in the brake calipers.
Lubricating Front Wheel Bearings
When removing one or both brake discs, check lu-
brication of front wheel bearings and the cavity of
the wheel hub and replenish if necessary (see operat-
ion
“Removing and Reinstalling Brake Disc”).
When carrying out other work on disc brakes which
does not necessitate the removal and installation of
the brake disc, lubricating wheel bearings is not
necessary.Checking Disc Brake Friction Pads for Wear
Whenever a disc brake equipped car is in for periodic
service, while the car is raised, the friction pads in
both brake calipers should be checked for wear by
making a simple measurement. Worn or oily friction
pads must be replaced.
Measure friction pad wear as follows:
1. Remove friction pads.
2. Using a one-inch micrometer, measure the thick-
ness of the pad and friction plate. See Figure
5B-23.Figure 58-23 Checking Brake Friction Pad Thickness
3. If any one of the four measurements is less than
-.280, replace all four friction pads. (Partial replace-
ment of friction pads would cause unequal braking.)
Removal and Installation of Friction Pads
1. Raise car and remove front wheels.
2. Drive dowel pins out of brake calipers toward
center of car. See Figure
5B-24. Dowel pins must be
driven inward because they are secured by enlarge
fluted inner ends.
3. Remove friction pads from brake calipers. See
Figure
5B-25.

DISC BRAKES58.17a tine cut file.Do not use any solvent except dena-
tured alcohol. Do not use a
metaIJic scraper too/.8. With a punch, drive one dowel pin from inboard
side through caliper and friction pads to stop. Install
new cross-shaped retaining spring under installed
dowel pin, then install second dowel pin. Loose tit-
ting dowel pins must be replaced.
9. Before operating vehicle, depress brake pedal sev-
eral times to adjust friction pads to brake discs.
Check brake fluid level and add fluid as necessary to
bring level up to “MAX” on reservoir.
Car owners must be informed that a break-in period
exists for new friction pads, and that they must avoid
unnecessary, forceful braking during the first 125
miles after installation of new friction pads.
Checking Brake Disc for Lateral Runout1. Remove front wheel assembly.
2. Remove front wheel bearing hub cap and spindle
nut cotter pin. Tighten spindle nut until all free play
is removed from wheel bearings.
3. To check disc runout, use Dial Indicator Set
J-
8001. Attach dial support C-clamp to an upper ball
joint attaching bolt as shown in Figure
5B-27. Posi-
tion dial indicator button against brake disc
l/2 inch
from outer circumference.
Figure 58-27 Checking Brake Disc Lateral
Runout4. Rotate disc, reading maximum dial indicator
movement. Maximum permissible runout is
,004
inch.5. If runout exceeds
0% inch, remove disc and hubassembly and true disc in a suitable disc turning
lathe, following manufacturer’s instructions. The
depth of cut on each side of disc should be just deep
enough to get a true flat surface.
6. After truing disc on both sides, check thickness
with a micrometer. A disc with a thickness of less
than ,394 inch is liable to warp after hard braking
and, therefore, must be discarded.
7. Reinstall brake disc and hub assembly, removing
all play from wheel bearings. Repeat runout check.
If runout still exceeds
,001 inch, replace brake disc.
8. Adjust front wheel bearings.
9. Reinstall front wheel assembly.
MAJOR REPAIR
REMOVING AND INSTALLING BRAKE CALIPER1. Remove left or right front wheel and remove fric-
tion pads from brake caliper.
2. Loosen brake line to brake caliper union nut sev-
eral turns. Unscrew brake caliper plus brake hose
bracket from steering knuckle. Remove it from brake
disc and swing it sideways. Then unscrew brake pipe
from brake hose and remove brake caliper and brake
pipe (bent pipe). To prevent brake fluid loss, close
brake hose with a plug.
3. Prior to installation,check contacting surfaces of
the brake caliper and steering knuckle to make sure
they are free of any burrs and dirt.
4. Install brake caliper on steering knuckle and
torque attaching bolts to 72
lb.ft. See Figure 5B-28.CAUTION: This disc brake
cah@er attachments fas-
tener is an important attaching part in that it could
affect the performance of vital components and sys-
tems, a,ld/or could result in major repair expense. It
must be replaced with one of the same part numberor with an equivafent part, if repfacement becomes
necessary. Do not use a replacement part of Jesser
quaJity ‘or substitute design. Torque vafues must be
used as specitied during reassembly to assure proper
retention of this part.
5. Attach brake pipe to brake hose.
6. Install friction pads and replace wheel.
REMOVING AND INSTALLING
BRAKE DISC
1. Jack-up and support front of car and remove front

DISC BRAKES5B- 19
CAUTION:
Fasteners in Steps 7 and 9 are important
attachingparts in that they cooId affect theperfom-
ante of vital components and systems, and/or couJd
resuJt in major repair expense. They must be re-
placed with one of the same part number or with an
equivaJent part if repJacement becomes necessary.
Do not use a replacement part
or Jesser quaJity or
substitute design. Torque
vaJues must be used as
specified during
reassembJy to assure proper reten-
tion of these parts.7. Install brake disc on wheel hub and torque attach-
ing bolts to 36
Ib.ft. If old brake disc is reused, pay
attention to locator marks on brake disc and wheel
hub.8. Prior to installing brake disc and hub assembly to
steering knuckle, check lubrication of both roller
bearings and quantity of grease in cavity of wheel
hub. If necessary, repack front wheel bearings.
9. Adjust front wheel bearing clearance and tighten
brake caliper to steering knuckle, attaching bolts to
a torque of 72
lb.ft. Prior to installing brake caliper
to steering knuckle, ensure that all contacting sur-
faces are free of dirt and burrs. Also make sure that
the friction pads are not damaged when sliding the
brake caliper onto brake disc.
10. Install wheel assembly, remove supports and
lower front of car.
REMOVING AND INSTALLING
BRAKE DISC SHIELD
Removal
1. Remove brake disc.
2. Remove disc shield from steering knuckle by
removing one Phillips head screw on the outside and
on the inside, the lower steering arm and disc shield
to steering knuckle bolt. Remove paper gaskets from
steering knuckle. See Figure
5B-32.Installation
1. Prior to placing new paper gasket between brake
disc shield and steering knuckle, lightly coat both
surfaces of paper gasket with chassis lubricant.
2. Install disc and tighten disc shield and steering
arm to steering knuckle bolt to a torque of 47
lb.ft.CAUTION:
This steen;Og arm and steering knuckJe to
backing plate
fisteneris an important attachingpart
in that it
couJd at&t the performance of viral com-
ponents and systems, and/or
couJd resuJt in major
repair expense. It must be replaced with one of theFigure 58-32 Brake Disc Shield Attached
to SteeringKnuckle
same part number or with an equivalent part, if re-
pJacement becomes necessary. Do not use a rep/ace-
merit part of Jesser quaJity or substitute design.
Torque values must be used as specitied during reas-
sembly to assure proper retention of this part.3. Replace one Phillips head screw on outside of disc.
See Figure
5B-32.DISASSEMBLY AND ASSEMBLY
OF BRAKE CALIPER
1. Remove brake pipe from brake caliper. If both
calipers have to be repaired, it is advisable to mark
them with “L” or “R” on removal to avoid errors
when installing parts, such as pistons, etc. The brake
caliper halves must not be disassembled during re-
pair work. All work, such as pressing out pistons,
replacing seals in brake caliper, is carried out with
the two caliper halves bolted together.
2. Pry clamp rings from rubber seals, using a screw-
driver (Figure
5B-26) and remove rubber seals.
3. Remove piston first from caliper rim half (Figure
5B-33), and then out of the caliper mounting half
(Figure
5B-34) of the brake caliper, using mounting
clamp J-22429. To be able to force the piston out of
the caliper rim half, block the piston in the caliper
mounting half with mounting clamp J-22429 as
shown in Figure
5B-33. To force the piston out of the
caliper mounting half, place the mounting clamp on
caliper rim half, as shown in Figure
5B-34, and
tighten wing nut so that the rubber plate seals off the
caliper rim half bore. Then connect compressed air
hose to brake line connection in the caliper mounting

DISC BRAKES5B- 21caliper half collars and the clamp rings are correctly
positioned on rubber seals.
12. Install brake caliper on steering knuckle, torqu-
ing bolts to 72 lb.ft.or with an equivalent part, if replacement becomes
necessary. Do not use a replacement part of lesser
quality or substitute design. Torque values must be
used as specified during reassembly to assure proper
retention of this part.
CAUTION: This disc brake caliper attachments fas-
tener is an important attaching part in that it couldatExt the performance of vital components and sys-
tems, and/or could result in
ma@r repair expense. It
must be replaced with one of the
same part number13. Attach brake pipe to caliper and torque to 22
lb.ft.14. Bleed brakes as necessary.
SPECIFICATIONSDISC BRAKE SPECIFICATIONS
General Specifications
DiscBrakeType. . . . . . . . . . .
Location
..,,.,..__....__.,,.,,,................,,,................,....Disc Type
.._.......................................................I.-. -.
......................2 Piston Fixed Caliper - Disc
........................................Front Wheels Only
..............................................Solid Cast Iron
useuameter...................................................,..............................................................9.370Disc Lateral Runout (Maximum)
......................................................................................,004DiscThickness
(New).........................................................................................................430DiscThickness(Minimum)
................................................................................................,394DiscParallelism(ThicknessTolerance)
...........................................................................0006Brake Shoe and Lining Type
........................................................................................Bonded
Brake Shoe and Lining Thickness (New)
..........................................................................
,550Brake Shoe and Lining Minimum Thickness Before
Replacement
....................................................................................................................,280Disc Brake Master Cylinder Bore
.......................................................................................8 10Disc Brake Caliper Cylinder Bore
- GT..........................................................................1.770Disc Brake Caliper Cylinder Bore Opel
1900 and Manta..............................................
1.890Disc Brake Shoe Adjustment
..............................................................................Self-Adjusting
Torque Specifications
Use a reliable torque wrench to tighten the parts listed, to insure proper
tightness without straining or distorting parts. These specifications are for
clean and lightly-lubricated threads only; dry or dirty threads produce in-
creased friction which prevents accurate measurement of tightness.
Bolt
Bolt
Bolt
NutName
BrakeCalipertoSteeringKnuckle
BrakeDisctoWheelHub
Brake Disc Shield to Steering Knuckle and Steering
Arm.
Brake Pipe to Caliper
.,.,...............................,......................Torque
Lb.Ft.
72
36
47
22

5C- 221973 OPEL SERVICE MANUAL
DRUM BRAKES
CONTENTS
Subject
DESCRIPTION AND OPERATION:
Description of Brake Mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .OperationofHydraulicServiceBrake
. . . . . . . . . . . . . . . . . . . . . . . .DIAGNOSIS:
BrakeTrouble
Diagnosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAINTENANCE AND ADJUSTMENTS:
BrakeAdjustment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Filling, Bleeding and Flushing Brake
Hydraulic System
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAJOR REPAIR:
Replace or Reline Brake Shoes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Inspecting and Reconditioning Brake Drums
. . . . . . . . . .Brake Wheel Cylinder Overhaul
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ReplacingBrakePipes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SPECIFICATIONS:
Brake Specifications
. . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DESCRIPTION AND OPERATION - DRUM
BRAKES
DESCRIPTION OF BRAKE MECHANISM
Wheel Brake Assemblies
Each rear wheel brake assembly uses two brake shoeswhich are actuated by a single wheel brake cylinder.
The center of the brake shoes are held against the
backing plate by a hold down pin, spring and re-
tainer. The bottom of the shoes pivot in a support
plate, and the top of the shoes rest directly on the
wheel brake cylinder push rods. The brake shoes are
connected by upper and lower return springs which
pull the sh6es back to resting position after applica-
tion. See Figure
5C-40.Two adjusting eccentrics at each wheel provide in-
dividual adjustment for each brake shoe to obtain
clearance with. the brake drum. An arrow on the
brake backing.plate circumference,shows direction in
which eccentrics must be turned to make adjust-
ment.
A hydraulic wheel cylinder is mounted on the back-Page No.5C-225C-245C-26
5C-275C-275C-28
5c-30
5c-305c-315c-31
Figure 5C-40 Rear Wheel Brake
ing plate between the upper ends of the brake
shoeand forces the shoes against the drum when pressure
is applied on the brake pedal. A lever mounted on
each rear shoe is used for applying parking brakes.

DRUM BRAKES5C- 23
Parking Brake Control System
The hand-operated parking brake lever is mounted
between the front seats on the propeller shaft tunnel.
A paw1 is riveted into the parking brake lever and is
actuated by a control rod provided with a spring
loaded push button. When the parking brake is ap-
plied, the parking brake lever is locked by the
paw1which engages the teeth on a stop plate. The parking
brake is disengaged by pressing the spring loaded
push button. See Figure
5C-41.
SPRING LOADED,-PUSH BUTTON
BRAKE LEVER
s\., \\,Figure
5C-4 1 Parking Brake Lever (Opel 1900 and
Manta)The GT arrangement of the parking brake is, with
the exception of the additional transmittal lever at
the floor panel, identical with that of the Opel mod-
els. The transmittal lever is attached to the propshaft
tunnel by means of a mounting support. See Figure
5C-42.The parking brake lever is connected with the front
parking brake pull rod. By means of an equalizer, the
front pull rod is connected to the forward portion of
a center cable. The center cable is routed rearward
through retaining guides and attaches at either end
to the lower end of a parking brake lever. See Figure
5C-43. The parking brake levers and struts actuate
the rear wheel brakes.
Service Brake Control System
-Standard Brakes
The service brake control system is a pedal operated
hydraulic system which applies the brakes at all four
wheels with equal pedal pressure. The hydraulic sys-
tem consists of a master cylinder (and attached trans-
parent fluid reservoir) connected by pipes and
1.PUSH BUTTON
2.THRUST SPRING
3.WASHER
4. PAWL CONTRO ROD
5. PARKING BRAKE LEVER
6.RIVET
7. HEX. HEAD BOLT
8.TOOTHED SEGMENT
9. PAWL WITH TWO TEETH
10.RUBBER CAP
11.THRUST ROD
12.PULL ROD
13.TRANSMITTAL LEVER
14.MOUNTING SUPPORT
15.BOLT
16. PARKING BRAKE CABLE
17. RETURN SPRING
sea2Figure 5C-42 Parking Brake Lever
(GT)flexible hoses to a wheel cylinder mounted between
the brake shoes at each rear wheel.
A mechanically-operated stop light switch is
mounted on a bracket just forward of the brake pedal
on the GT and just rearward of the brake pedal on
the Opel 1900 and Manta. With brake pedal released,
the switch plunger is fully depressed against the
switch actuating lever. See Figures
5C-45 and 5C-46.Any time the stop light switch fails, the stop lights
will stay on at all times.

DRUM BRAKES5C- 25PISTONCYLINDER HOUSING
BLEEDER VALVE
SC-47Figure
5C-47 Wheel Cylinder Exploded View
cups are of a special heat resisting rubber. Theagainst the ends of the shoes. Rubber boots en-
inlet port for brake fluid is located between theclose both ends of the cylinder to exclude foreign
pistons so that when fluid pressure is applied,
matter. A valve for bleeding brake pipes and
both pistons move outward in the wheel cylin-wheel cylinder is located in the back of the cylin-
ders. The pistons impart movement to the brake
der casting and extends through the brake backing
shoes of the rear wheel brakes by bearing directly
plate assembly. See Figure 5C47.