1973 OPEL GT-R brake pads

LUBRICATION AND MAINTENANCE OC-7SERVICESLUBE AND GENERAL MAINTENANCE
Vehicle operation under conditions such as heavy
dust, continuous short trips, use of other than un-
leaded or low lead fuels or pulling trailers, is not
considered normal use and therefore more frequent
maintenance will be required. Such additional
maintenance requirements are included where appli-
cable.
Engine OilChange each 4 months or
3,COO miles, whichever
occurs first, or each 2 months or
3,ooO miles when
the vehicle is operated under the following condi-
tions: (a) driving in dusty conditions, (b) trailer pull-
ing, (c) extensive idling or (d) short-trip operation at
freezing temperatures (with engine not thoroughly
warmed-up).Engine oils have a definite effect on ease of starting,
oil economy, combustion chamber deposits and en-
gine wear. It is recommended that a” oil which,
according to the label on the can is; (1) intended for
service SE and (2) passes car makers’ tests be used.
Oils confotming to these types contain detergent ad-
ditives. -
Select the proper oil viscosity from Figure OC-3.
Engine Oil FilterReplace at the first oil change and every other oil
change thereafter using Part No. 7965051 or equiva-
lent.
ChassisLubricate transmission shift linkage, hood latch and
parking brake cable guides and linkage.
Fluid LevelsCheck level of fluid in brake master cylinder, battery,
engine, axle, transmission and windshield washer.
Engine coolant also should be checked for proper
level and for corrosion and freeze protection to at
least -20°F or to the lowest temperature expected
during the period of vehicle operation. Proper engine
coolant also provides corrosion protection.
Any significant fluid loss in any of these systems or
units could mea” that a malfunction is developing
and corrective action should be taken immediately.
A low fluid level in the brake master cylinder front
reservoir could also be a” indtcator that the disc
brake pads need replacing.
The engine oil should be maintained at proper level.
The best time to check it is before operating the
engine or as the last step in a fuel stop. THIS WILL
ALLOW THE NORMAL OIL ACCUMULA-
TION IN THE ENGINE TO DRAIN BACK IN
the crankcase. To check the level, remove the oil
gauge rod (dipstick), wipe it clean, and reinsert it for
a” accurate reading. The oil level should be main-
tained in the safety margin, neither going above the
“FULL” mark “or below the “ADD OIL” mark.
See Figure OC-4.
DIP STICK MUST BE
INSERTED TO STOP
---L- -FULL+, 1 OT. ,-ADD
OIL
Figure OC-4 Engine Oil Dipstick
All models are equipped with tandem brake cylin-
ders. Maintain fluid level between MIN and MAX
marks on reservoir. See Figure OC-5. When adding
fluid use Delco Supreme No. 11 or equivalent.
TiresTo equalize wear, rotate tires as illustrated in Figure
OC-6.Adjust clutch when necessary as indicated by the
clutch warning lamp on Opel 1900 and Manta or

CC-10 1973 OPEL SERVICE MANUAL
wiper blades. Check amount and direction of fluid
sprayed by washers during use.,
E. Defrosters - Check performance by moving con-
trols to “DEF” and noting
am$nmt of air directed
against the windshield.
I
F. Wheel Alignment and
Balabce - In addition to
abnormal tire wear, the need fbr wheel alignment
service may be indicated by a pull to the right or
!eftwhen driving on a straight and level road. The need
for wheel balancing is usually
iddicated by a vibra-
tion of the steering wheel or
se;+ tihile driving at
normal highway speeds.I
IG. Brakes
- Be alert to illumiriation of the brake
warning light or changes in braking action,
SUCK as
repeated pulling to one side, unusual sounds when
braking or increased brake pedal travel. Any of thesecould indicate the need for
brakk system inspection
and/or service.
H. Parking Brake and Transmission “PARK”
Mechanism
- Check parking brake holding ability by
parking on a fairly steep hill and restraining the vehi-
cle with the parking brake only.
eon cars with auto-
matic transmissions, check the holding ability of the
“PARK” mechanism by releasing all brakes after
the transmission selector lever hak been placed in the“P” position.
I. Glass
- Check for broken, scrritched, dirty or da-
maged glass on vehicle that
coulld obscure vision’or
become an injury hazard.
J. Lights and Buzzers
- Check all instrument panel
illuminating and warning lights,’ seat belt reminder
light and buzzer, ignition key
b&er, interior lights,
license plate lights, side marker! lights, headlamps,
parking lamps, tail lamps, brake lights, turn signals,
backup lamps, and hazard warding flashers. Have
someone observe operation of
&ach exterior light
while you activate the controls: The operation of
instrument panel warning lights is covered in the
“Starting and Operating“ section of your
Own&%
Manual.K. Transmission Shift Indicator
‘- Check to be sure
automatic transmission shift
indiCator accurately i”-
dicates the shift position selected.
I
CAUTION: Before making thk check below,I
be sure to have a clear dist&e ahead and:
behind the car, set the parking brake and
firmly apply the foot brake.
Do not depress
accelerator pedal. Be prepared to
turn off ’
ignition switch
immediat+y if engine
should start.L. Starter Safety Switch (Automatic Transmissibn
Cars)
- Check starter safety switch by placing the
transmission in each of the driving gears while
at-tempting to start the engine. The starter should oper-ate only in the Park (“P”) or Neutral (“N”)
positions.
M. Horn
- Blow the horn occasionally to be sure thatit works. (Ignition switch must be in the “ON” posi-
tion.)
N. Seat Back Latches
- Check to see that seat back
latches are holding by pulling forward on the top of
each folding seat back.
0. Rearview Mirrors and Sun Visors
- Check that
friction joints are properly adjusted so mirrors and
sun visors stay in the selected position.
P. Door Latches
- Check for positive closing, latch-
ing and locking.
Q. Hood Latches - Check to make sure hood closesfirmly by pressing on the hood at the latching point
after each closing. Check also for broken, damaged
or missing parts which might prevent secure latch-
ing.R. Fluid Leaks
- Check for fuel, water, oil or other
fluid leaks by observing the ground beneath the vehi-cle after it has been parked for a while. If gasoline
fumes or fluid are noticed at any time, the cause
should be determined and corrected without delay
because of the possibility of fire.
S. Exhaust System
- Be alert to any change in the
sound of the exhaust system or a smell of fumes
which may indicate a leak.
Head Restraints
- Check that no head restraint
components are missing, damaged or loose. (Does
not apply to GT Models).
Disc BrakesCheck brake pads and condition of rotors while
wheels are removed during tire rotation. (Note belowregarding more frequent checks also applies to disc
brakes.)
Parking and Drum BrakesCheck drum
brake linings and other internal brake
components at each wheel (drums, wheel cylinders,
etc.). Parking brake adjustment also should be
checked whenever drum brake linings are checked.
NOTE: More frequent checks should be
made if driving conditions a.nd habits result
in frequent brake application. When brakes
require relining, it is recommended thatyou use those genuine General Motors
parts specified for your car,and Delco fluid
as required.

5B- 10 1973 OPEL SERVICE MANUAL
DISC BRAKES
CONTENTS
Subject
DESCRIPTION AND OPERATION:
Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . .DIAGNOSIS:
DiscBrakeTroubleDiagnosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MAINTENANCE AND ADJUSTMENTS:
Disc Brake Maintenance
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Checking Disc Brake Friction Pads for Wear
. . . . . . . . . .Replacing Friction Pads
Checking Brake Disc for Lateral
Runout. . . . . . . . . . . . . . . . . .MAJOR REPAIR:
RemovingandInstallingBrakeCaliper. . . . . . . . . . . . . . . . . . . . . .Removing and Installing Brake Disc
. . . . . . . , . . . . . . . . . . . . . . . . . .
RemovingandInstallingBrakeDiscShield. . . . . . . . . . . . . .Disassembly and Assembly of Brake Caliper
. . . . . . . . . .SPECIFICATIONS:
Disc Brake Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page No.
58-1058-l
1
58-12
58-15
SB-15
5&17
56-17
58-17
58-195519
58-21
DESCRIPTION AND OPERATION
DESCRIPTIONThe front wheel disc brake consists of two major
parts: The brake disc and the brake caliper with the
two friction pads. See Figure
5B-20.The brake disc is attached to the inside of the wheel
hub flange by four bolts and centered on a shoulder
of the hub. The brake caliper consists of two halves:
the mounting half, arranged on the inside of the
brake disc, and the rim half. The two halves are
firmly attached to each other by four bolts. Two
flanges on the mounting half serve as attachment of
the brake caliper to the steering knuckle. The brake
caliper is positioned behind the front suspension
cross member at steering knuckle spindle level. It is
attached to the steering knuckle by two bolts. Both
caliper halves act as brake cylinders and each houses
a piston and a fluid seal. The fluid seal, of square
cross section, is positioned in an annular groove of
the caliper bore, preventing fluid leakage past the
piston and entry of water and dirt. The pistons and
caliper half bores are protected against entry of waterFigure 58.20 Left Front Disc Brake Assembly
and dirt in brake disc direction by a rubber seal, held
on the caliper half collar by a clamp ring and against

DISC BRAKES5B- 11
rLF 5.2. RUBBER FLUID SEALS6.3. HOLLOW PISTONS7.
AL5
3Figure 58.21 Left Front Disc Brake
- Emloded View
the piston circumference by its inherent tension. See
Figure
5B-21. Both pistons are hollow. The open end
of each piston faces the brake disc.
A sheet metal spacer plate with two impressions for
preventing the piston from rotating is installed be-
tween each piston and friction pad and secured by
the friction pad dowel pins. The two friction pads are
positioned on the right and left of the brake disc
recesses in the caliper halves. Each friction pad con-
sists of a backing plate with friction material, which
is abrasive-coated, bonded to it. The friction pad
assemblies are held in position in the brake caliper by
two dowel pins, secured by slit dowel pin retainers,
and by a cross-shaped retaining spring which is pre-
loaded and positioned under the dowel pins, thus
pressing the friction pads and spacer plates firmly
against the pistons. The front brake line leading from
the brake master cylinder attaches to a distribution
tee from which a brake line leads to each front wheel
caliper. The caliper bores are interconnected by fluid
ducts within the caliper halves.
The front wheel disc brakes have self-adjusting pis-
tons. See Figure
5B-22.The adjustment of the pads is effected by the pistons
which push the friction pads ahead towards the
brake disc for a distance equivalent to the amount of
friction pad wear. This means that the greater the
wear the closer the pistons move towards the brake
disc. A running clearance exists between friction
pads and brake disc when the brakes are in “off”
position. This running clearance is provided by the
rubber fluid seals which are positioned in the caliper
half bores and which tightly grip and exert their
pre-load pressure on the pistons. The rubber fluid
seals also prevent the pistons from being pushed into
the caliper half bores more than the distance equiva-
lent to the running clearance. As the friction pads are
adjusted by the pistons, there must be no static pres-
sure in the front brake circuit when the brakes are in“OR position. Non-existence of a static pressure in
the front brake circuit is achieved by eliminating the
check valve in the brake master cylinder on the front
brake circuit. During brake application the pressure
from the brake master cylinder is transferred to the
pistons in the brake caliper. The pistons move ahead
and press the friction pads against both friction
SW-faces of the rotating brake disc. The force exerted on
the brake pedal determines the pressure of the fric-
tion pads against the brake disc. On releasing the
brake pedal, the brake lines of the front brake circuit,
including the caliper half bores, are relieved of
hy-OPERATION

5B- 121973 OPEL SERVICE MANUAL
A = BRAKE ON
THE RUBBER FLUID SEAL TIGHTLY GRIPPING PISTON
IS DEFLECTED IN DIRECTION OF PISTON TRAVELAFRICTION PAD
BRAKE DISCRUBBER FLUID SEALBRAKE
IICALIPER
IPISTON
I
CE BETWEEN RUNNING CLEARAN
FRICTION PAD AND BRAKE DISC
B = BRAKE OFFBTHE PISTON IS RETRACTED BY THE AMOUNT OF
RUBBER FLUID SEAL DEFLECTION. THIS AMOUNT
IS EQUAL TO RUNNING CLEARANCE.SBZZ
Figure 58-22 Rubber Fluid Seal -Automatic Piston Retractiondraulic pressure, and the friction pads and pistonsmove away from the brake disc, leaving a small run-
ning clearance. The brake disc can now rotate freely.
The amount of brake travel is dependent upon the
amount of running clearance. For this reason therunout of the brake disc should be checked, besides
bleeding of the brake system and adjusting the rear
brake shoes, when the pedal free travel is too great.during braking, the rubber seals in the annular
grooves of the brake caliper bores deflect laterally in
the direction of piston movement. See Figure
5B-22,View (A). The seal remains deflected for the duration
of the braking operation. After braking, the caliper
bores are relieved of hydraulic pressure and the rub-
ber seals resume their normal position, thus pulling
or retracting the pistons. The distance traveled by
the pistons is equal to that of the running clearance
between brake disc and friction pads.
The running clearance between brake disc and
fric-tion pads is attained as follows: When the pistons in
the caliper halves are moved towards the brake discThe shifting of the pistons in the direction of the
brake disc due to friction pad wear has no effect on
the running clearance. The running clearance re-mains the same in all piston positions.
DIAGNOSIS
DISC BRAKE TROUBLE DIAGNOSIS
ConditionPulls
Possible Cause
I. Incorrect tire
pressures.Correction1. Inflate evenly on both sides to
the recommended pressures (see
Owner’s Manual).

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.

5B- 19i973 OPEL SERVICE MANUAL
Figure
56-24 Removing Dowel Pins
Figure 56-25 Removing Friction Pads
4. Check rubber seals for wear. If rubber seals are
hardened, brittle or cracked, they must be replaced
as follows:
(a) Remove brake caliper from steering knuckle and
brake disc. Leave hose attached to brake caliper.
(b) Remove seal clamp rings with screwdriver and
remove seal rings from calipers. See Figure
5B-26.(c) Install new rubber seals and clamp rings. Make
sure rubber seal is properly seated. Make sure clamp
ring is correctly positioned on rubber seal,Figure 56-26 Removing or Installing Rubber Seal
Clamp Ring
(d) Attach brake caliper to steering knuckle and
torque bolts to 72
Ib.ft. Prior to installation of
caliper, make sure contacting surfaces of both caliper
and steering knuckle are perfectly clean and free of
any burrs.
CAUTION: This disc brake caliper attachments fas-
tener is an important attaching part in that it could
affect the performance of vital components and sys-
tems, and/or could
result in major repair expense. It
must be replaced with one of the same part number
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.5. Before installing new friction pads, press both pis-
tons of each caliper to bottom of their bores, using
Return Clamp J-22430.
While pressing piston into
bores, open caliper bleeder valve to prevent excess
brake fluid from overflowing master cylinder con-tainer As soon as pistons are bottomed, tighten
bleeder valve.
6. Check brake disc for lateral runout.
7. Install new friction pads into brake caliper. Fric-
tion pads must be free enough to be easily moved in
their caliper recesses. See
Figure X3-25.If new friction pads are not free, it will be necessary
to remove pads and clean recesses and recess corners
with a wooden spatula and then with denatured al-
cohol and a brush. After cleaning, blow out recesses
with compressed air. Remove any high spots on
edges of friction pads contacting caliper recesses with

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