Failure Modes Check-Out - Komatsu 930E-2 Shop Manual

Failure Modes Check-Out

29. Start engine and allow low brake accumulator
pressure (LAP1 gauge) to stabilize at or above
2700 psi (18,613 kPa).
30. Turn the key switch OFF to shut down the engine,
and allow approximately 90 seconds for the steer-
ing accumulators to bleed down.
31. Disable the steering pressure switch by unplug-
ging the diode between circuits #33 and #33F on
diode board DB1 in the auxillary control box or by
disconnecting the wires at the steering pressure
switch.
32. Turn the key switch ON. After 2 minutes, record
the low accumulator pressure (LAP1) gauge read-
ing.
If pressure decreases to less than 2100 psi
(14,480 kPa), internal system leakage is ex-
cessive. The source of the leakage must be
identified and repaired.
* Record on data sheet.
33. Very slowly, open the front brake accumulator
bleeddown valve a small amount ([NVF] 16, Fig-
ure 4-1) while observing LAP1 decreasing pres-
sure.
The low brake pressure lamp and buzzer
must activate when pressure drops to 1850
±75 psi (12,755 ±517 kPa).
* Record on data sheet.
When the LAP1 pressure reaches 1650 psi
(11,375 kPa) brake pressures "B1" and "B2"
should begin to rise (auto apply).
* Record on data sheet.
34. Close the front brake accumulator bleeddown
valve. Start engine and allow low brake accumu-
lator pressure (LAP1 gauge) to stabilize at or
above 2700 psi (18,613 kPa).
35. Turn key switch OFF to shut down engine and
allow the steering accumulators to bleed down
completely.
J4-6
36. Turn key switch ON. Very slowly, open the rear
brake accumulator bleeddown valve a small
amount ([NVR] 19, Figure 4-1) while observing
LAP1 decreasing pressure.
Verify the low pressure warning lamp and
buzzer activate within 100 psi (690 kPa) of
the pressure recorded in step 33.
* Record on data sheet.
Verify the brake pressures "B1" and "B2" be-
gin to rise within 100 psi (690 kPa) of the auto
apply set point pressure recorded in step 33.
* Record on data sheet.
37. Reinstall diode on diode board DB1 or connect
wire harness at steering pressure switch.
38. Start engine and allow low brake accumulator
pressure (LAP1 gauge) to stabilize at or above
2700 psi (18,613 kPa).
39. Shut down engine but do not turn key switch OFF.
(Do not allow steering accumulators to bleed
down.)
40. While observing pressure gauges, make repeated,
slow, brake applications until auto apply comes
on.
Auto apply must not actuate prior to the sixth
pedal application.
* Record on data sheet.
41. Turn the key switch OFF and allow the steering
accumulators to bleed down.
42. Open both accumulator bleeddown valves and
bleed down the entire brake system. Close valves
after all pressure is released.
43. Disconnect the hose (4, Figure 4-4) that supplies
oil to the brake valve ("P2" port), front brake circuit,
by removing at the tee attached to the bottom of
the hydraulic cabinet (brake manifold port "AF1").
Cap the tee fitting, but hose must be vented to
atmosphere.
44. Start engine and allow low brake accumulator
pressure (LAP1 gauge) to stabilize at or above
2700 psi (18,613 kPa).
Brake Circuit Checkout J04025