From model '83
CHECKING BRAKE BOOSTER SYSTEM

Stop engine and operate brake pedal about 20
times with a force equal to full stop braking
action to discharge the hydraulic reservoir.
Pull off wires and detach warning switch.
Apply Special Tool 34 3 160.
Installation: Tightening torque¹).


¹) See Specifications

Connect Special Tool 32 4 000 (pressure meter)
on Special Tool 34 3 160 (adapter).
Shut both valves (1 and 2).

Checking Pressure Regulator and Booster for
Leaks:
Start engine and observe pressure meter.
Stop engine after reaching upper switching off
pressure¹).


¹) See Specifications

If the reservoir pressure (pressure meter reading)
drops more than 5 bar (71 psi) within 5 minutes,
disconnect return line on the pressure regulator.
If oil leaks from return line bore in pressure regulator,
pressure regulator leaks and must be replaced.
If oil does not leak and reservoir pressure still
drops, brake booster has a internal leak and
must be replaced.

Checking Function of Hydraulic Reservoir
Operate brake pedal about 20 times to reduce
the reservoir pressure (pressure meter reading)
to zero.
Start engine and observe pressure meter.
Pressure meter should show a value according to
diagram below immediately.
If this value is not reached or exceeded, replace
the hydraulic reservoir.

Gas Charging Pressure/Hydraulic Reservoir Temperature Diagram
A = Gas charging pressure in bar
B = Hydraulic reservoir temperature in ° C
Permissible Gas Charging Pressure of Hydraulic Reservoir
Depending on Pertinent Temperature Conditions

Checking Function of Pressure Regulator:
Start engine.
Pressure continues rising to upper switching
pressure¹).
Operate brake pedal with engine running to
drop reservoir pressure (pressure meter reading)
to lower switching pressure¹).
Afterwards pressure regulator will switch to
charging reservoir (pressure rises again).
Replace pressure regulator, if test values do not
conform with specifications.
Drop reservoir pressure (pressure meter reading)
to zero by operating brake pedal about 20
times.
Remove pressure meter and check oil level in
supply tank.


¹) See Specifications

Checking Function of Brake Booster and Tandem
Brake Master Cylinder:
Remove and install front wheel 36 10 300.
Unscrew bleeder screw on caliper.
Connect and bleed pressure tester.


* See Specifications

Mount pedal force meter on brake pedal.
Apply specified force¹) on brake pedal with
engine running (full hydraulic reservoir).
The hydraulic line pressure of the service brake
system should then be the specified value¹).
If these values are not reached on a fully intact
service brake system, replace brake booster.
Note: This test does not include checking the
service brake system for leaks.


¹) See Specifications