Opel 1900 1973 Service Manual page 264

C o n d i t i o n
Grabby Brakes (Apparent Off-
and On Condition)
Brakes Fail to Release
MAINTENANCE AND ADJUSTMENTS
CHECKING BRAKE BOOSTER OPERATION
The operation of the brake booster can be checked by
simple means and without any special devices.
1. With engine off, first clear the booster of any
vacuum by depressing brake pedal several times.
2. Then depress brake pedal and start engine. If the
vacuum system is working correctly, the brake pedal,
kept under even foot pressure, moves farther down-
wards due to the additional pressure developed by
the booster. Should the brake pedal not move farther
downwards, the vacuum system is deficient. In this
case check the vacuum hose to booster, to vacuum
control valve and to engine intake manifold connec-
tions.
3. If the vacuum system operates properly, the defect
is in the brake booster itself. A dirty filter impairs or
POWER BRAKE BOOSTER AND MASTER CYLINDER
P o s s i b l e C a u s e
1. Broken or damaged
hydraulic brake lines.
2. Insufficient fluid in
master cylinder.
3. Defective master cylinder
seals.
4. Cracked master cylinder
casting.
5. Leaks at front disc brake
calipers or rear wheel
cylinders
in pipes or connections.
6. Air in hydraulic system.
1. Blocked passage in power
piston.
2. Air valve sticking shut.
3. Broken piston return spring
master cylinder.
4. Tight pedal linkage.
even prevents air from entering into the booster and
thereby the formation of a difference in pressure in
the vacuum cylinder.
Repairs cannot be carried out on the brake booster.
If no deficiency can be found in the vacuum system
or filter, the brake booster has to be replaced.
Under normal operating conditions the brake
booster requires no service. However, under adverse
conditions such as frequent driving on sandy or
dusty roads, the filter and sound deadener should be
replaced occasionally. To do so, the brake booster
must be removed but it isn't necessary to detach the
master cylinder.
BRAKE BOOSTER FILTER SERVICE
Under normal operating conditions the filter need
not be exchanged for a new one.
Under adverse operating conditions - frequent
C o r r e c t i o n
1. Inspect and replace, as
2. Fill reservoirs with approved
brake fluid check for leaks.
3. Repair or replace, as
necessary.
4. Replace
5. Inspect and repair, as
necessary.
6. Bleed system.
1. Inspect and repair or replace,
as necessary.
2. Check for proper lubrication of
air valve "0" ring.
3. Replace
5. Repair or replace, as
necessary.