6. Before installing, shims must be measured to in-
sure that the proper thickness is being used. Install
shims of correct thickness to obtain desired clearance
and reassemble and install pinion shaft lock pin. In-
stall thrust washers with concave side towards differ-
ential case.
7. Using Special Tool J-24093, along with a foot-pound torque wrench, check torque to turn gears
using the following procedure:
a. Install axle shaft into a vise and position differen-
tial case onto axle shaft. See Figure
4B-25.Figure 48-23 Raising Side Gear Against Case
Figure 48.24 Measuring Concave Washer Thickness
AX,EXAMPLE:
1.Dial indicator reading * .095.
2. Subtract concave thrust washer thickness
+ -.oso.
3.Total + ,045.
4.Subtract an additional .002 *.002.
5. Shim thickness to be used
+ .043.
5. Turn case over and repeat the above procedure to
check other side gear to differential case clearance.Figure 48.25 Axle Shaft Installed in Vise
b. Insert Special Tool J-24093 into opposite side gear,
attach a torque wrench, and check torque to rotate
gear. S& Figure
4B-26. Permissible torque to turn
gears is 14
l/2 to 17 l/2 footpounds.
c. It is necessary to check rotating torque of both side
gears.8. If torque is not correct, it will be necessary to
reshim differential gears. Add first at one side one
shim of the next higher or lower thickness. If this is
not enough, reshim both sides completely.
9. Install ring gear on case making certain their mat-
5A- 61973 OPEL SERVICE MANUAL
ing on dusty and sandy roads - the filter and sound
deadener should occasionally be replaced. To do so,
brake booster has to be removed without detaching
brake master cylinder.
Proceed as follows:
1. Remove protective cap (boot).
2. On the GT only, pry retainer from housing
using a screwdriver. See Figure
SA-6.Figure 5A-6 Brake Booster Filter (GT)
3. With a pointed tool remove air silencer and filter
out of control housing bore and pull it off thrust rod.
4. Install new filter and air silencer. On the GT, the
smooth side of the filter must face towards the inside.
The radial slots in filter and deadener must be stag-
gered to each other by 180 degrees.
5. Slide retainer over control housing (GT only) and
seal it with light plastic hammer strokes. Slide pro-
tective cap over control housing and slip it onto
brake booster housing.
VACUUM CONTROL VALVE SERVICE
A vacuum control valve is installed into the vacuum
hose between intake manifold and brake booster. It
serves to prevent air from flowing back (vacuum
release), when engine is shut off.
The vacuum control valve cannot be disassembled
and has to be replaced, if defective. On replacement,
note the following:
1. The vacuum control valve should be located near
the intake manifold. Therefore, the short vacuumhose has to be installed between intake manifold and
vacuum control valve and the long hose between
vacuum control valve and brake booster.
2. The arrows on the vacuum control valve housing
must point towards the intake manifold, otherwise
no air can be drawn out of the brake booster which
renders the brake booster ineffective.
3. The connections of the vacuum hoses to the intake
manifold, vacuum control valve and brake booster
must be airtight. For this reason make sure. that the
hose clamps are properly installed.
MAJOR REPAIR
BRAKE BOOSTER REMOVALAND INSTALLATION
Removal
1. Disconnect brake pipes from master cylinder.
Place a cloth under the master cylinder and brake
pipes to absorb any brake fluid drippings.
2. Disconnect vacuum hose from brake booster.
3. Remove four nuts and washers attaching brake
booster to brake booster support.
4. On the GT only, remove master cylinder support
to fender skirt bolts.
5. On the GT, loosen thrust rod lock nut and un-
screw the piston push rod while holding the master
cylinder brake booster assembly. On the Opel
1900and Manta, remove the nut and bolt attaching clevis
on the pedal.
6. Remove assembly from car.
7. Disconnect master cylinder from brake booster.
Installation
CAUTION: Fasteners in the folkwing steps are im-
portant attaching parts in that they could affect the
performance of vital components and systems, and-
/or could result in major repair expense. They must
berep/aced, with one of the same part number or with
an equivalent part if replacement becomes necessary.
Do not
use a replacement part or lesser quality or
substitute design. Torque values must be used as
specified during reassembly to assure proper reten-
tion of these parts.1. Using a new front housing seal, assemble master
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.
58.201973 OPEL SERVICE MANUAL
half, and blow out pistons, carefully regulating air
flow. When removing pistons, proceed with extreme
caution and always keep the fingers ofthe hand hold-
ing the brake caliper away from the piston.
Figure 55.33 Removing Caliper Rim Half Piston
Figure 58-34 Removing Caliper Mounting Half Piston
4. Pry rubber fluid seals out of the annular grooves
in the caliper half bores. See Figure
5B-35.5. Check all parts of the brake caliper for wear. If the
caliper half bores are scored or rusted, use a new
complete brake caliper and friction pads. Small, light
rust spots in the caliper half bores or on the pistons
can be removed with fine emery cloth. If pistons are
damaged, even though the caliper half bores are inFigure 58-35 Removing Rubber Fluid Seal From
Caliper Boresgood condition, the piston must be replaced. The
rubber fluid seals and rubber seals with
clapp rings
for the pistons are to be replaced every time repair
work is carried out on the brake caliper.
6. Thoroughly clean all reusable parts
- complete
brake caliper and pistons
- with denatured alcohol
and dry with compressed air. Prior to cleaning, screw
bleeder valve out of caliper.
7. Lightly coat new rubber fluid seals with brake
fluid and insert fluid seals into grooves of brake
caliper bores.
8. Place brake caliper into vise to install pistons.
After installing one piston, change position of brake
caliper in vise to install second piston. The piston to
friction pad spacer plates should be used as a gauge
to locate relieved edge of piston at 20 degrees to
horizontal during piston installation. See Steps
9-IO-
11-12.9. Place caliper mounting half in vise and coat its
bore and piston lightly with brake fluid. Then push
piston, with hollow end towards brake disc, into the
caliper bore. Turn piston so that the relieved edge
faces downwards at an angle of 20 degrees and facing
in brake disc direction. The guide surface in the
caliper half recess at the brake pipe connection side,
will properly align the piston. Push piston into
caliper bore up to the stop.
10. Change position of brake caliper and install sec-
ond piston in the same manner.
11. Install new rubber seals with clamp rings. Make
sure that the rubber seals are properly seated on the
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
6A- 8 1973 OPEL SERVICE MANUAL
Actual adjustment is made by backing off adjusting
nut at the rocker arm until clearance exists between the valve stem, rocker arm, and lifter. Then slowly
tighten adjusting nut until clearance is eliminated.
When clearance is eliminated, turn adjusting nut one
full turn (clockwise). This positions the hydraulic
piston of the hydraulic lifter mid-point in its total
available travel, and no further adjustment is re-
quired.
MAJOR REPAIR
ENGINE ASSEMBLY REMOVAL AND
INSTALLATION
Removal (Opel 1900 and Manta)’
The engine assembly on the Opel 1900 and Manta
can be removed together with the transmission
through the top of the engine compartment.
1. Remove hood (scribe hood hinge to hood mount-
ing location).
2. Disconnect battery negative cable.
3. Drain coolant at lower radiator hose.
4. Remove upper and lower radiator hoses.
5. Remove radiator and fan
shrbud.
6. Disconnect heater hoses.
7. Disconnect brake booster
vacuum hose.
8. Remove air cleaner.
9. Disconnect electrical connections and accelerator
linkage. 10. Remove console.
11. Remove shift lever boot, plate, and shift lever.
12. Raise car on hoist.
13. Disconnect fuel line at pump.
14. Remove front stone shield.
15. Disconnect speedo-cable, back-up light switch,
and clutch cable.
16. Remove drive shaft. I
17. Disconnect exhaust pipe
ar$l bell housing sup-
port.
18. Disconnect transmission support. See Figure
6A-7. 19. Remove engine mount bolts. See Figure
6A-8.
20. Attach hoist chains.
21. Lift engine and transmission assembly out of car.
Figure 6A-7 Transmission Support Bolts . Opel 1900
and Manta Series
Figure
6A-B Engine Mount Bolts - Opel 1900 and
Manta Series
Removal (GT)
The removal and installation of the 1.9 liter engine is only possible towards the floor and from below
Fig, 6A-9 Left Front Engine Suspension with Cross
Member (GT)