Troubleshooting
Fig. 28
Instructions on Design, Operation, Maintenance and Inspection
41
1.6.5 Checking the maximum pressure and
t
he leakage oil of the steering gear
For steering systems with pressure relief
ahead of tool [1]: Variant ➀
➀➀
➀
Between the lock stops, insert tool [3] or
approx. 15 mm thick thrust pads (Fig. 28) en-
suring that the steering motion is stopped 1/2
to 3/4 steering wheel turn before reaching the
axle stop/lock stop. The restriction of the
steering motion must take place at tool [3] or
at the said thrust pads and must not be done
by the piston in the steering gear.
Attention:
A tool under pressure may be ejected - avoid any direct visual contact with the tool. Danger of
accidents by squeezing.
Use the special tool specified by the vehicle manufacturer for the axle version in question.
At engine idling speed, rotate the steering wheel to the stop and continue to turn for abt. 5 seconds
with an effort of 100...200 N at the steering wheel. Read the maximum pressure and the leakage
oil.
Repeat this test in the opposite direction of rotation.
Maximum permissible leakage oil values: Type 8090: 2.0 dm
3
/min
Types 8095...8098: 2.5 dm
3
/min
Checking the leakage oil at a reduced flow rate:
Set tool [1] (ZF Servotest) 6.. to a flow rate which is 0.5 dm
3
/min higher than the maximum permis-
sible leakage oil value.
Repeat the leakage oil test as described above. The leakage oil value measured in this repetition
test must not exceed the value measured previously - see above.
Cause of insufficient maximum pressure/too much leakage oil:
Pressure relief valve and/or replenishment valve defective.
Pressure cut-off of steering limitation valve comes too early - refer to Chapter III., para. 5
for setting.
Seals in the steering gear defective.
For steering systems with pressure relief aft of tool [1]: Variant ➁
➁➁
➁
The shut-off valve (4) must be closed completely and the throttle valve (5) must be closed progres-
sively until a pressure is achieved that is 30 bar lower than maximum pressure. Re-open the
shut-off valve (4).
Repeat this test as described above.
1.6.6 Checking the return to neutral of the valve
Note:
Make sure the steering column has sufficient clearance (floor carpets, coverings).
By rotating the steering wheel, close the steering valve, thus causing maximum pressure to build
up. Then rotate the steering wheel back until idle pressure is available. Next, raise the pressure
to idle pressure +10 bar.
Release the steering wheel and watch the pressure which must drop to idle pressure (at maximum
0.5 bar higher) within 1 second.
Example:Idle pressure: 4.0 bar Maximum permissible value: 4.5 bar
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