Brake System Checkout - Komatsu 930E-2 Shop Manual

BRAKE SYSTEM CHECKOUT

NOTE: Unless otherwise specified, perform the follow-
ing checks with engine running, Rest switch in the ON
position, park brake ON and brake lock released.
9. Apply brake lock. Turn the parking brake switch
to the OFF position:
Verify park brake indicator lamp is off.
Verify park brake release pressure (gauge in-
stalled in "PK2" port in hydraulic cabinet) is
2700 ±100 psi (18,615 ±690 kPa).
* Record on data sheet.
10. Cycle park brake several times to assure crisp
application and release of oil pressure when
switch is OFF.
11. Place parking brake switch in the ON position and
release the brake lock.
12. Install a 3000 psi (20,685 kPa) pressure gauge at
the "LBP" (9, Figure 4-5) and "RBP" (8) test ports
on the junction block at the left front corner of the
rear axle housing.
13. Very slowly depress brake pedal. Force feedback
of pedal on foot should be smooth with no abnor-
mal noise or mechanical roughness.
14. Slowly depress brake pedal:
Verify brake indicator lamp and stop lights illu-
minate at 75 ± 5 psi (517 ±34 kPa) rear brake
pressure.
* Record on data sheet.
15. Quickly and completely depress pedal. Verify that
within 1 second after brake is applied:
Left rear brake pressure ("LBP", 9) reads
2400 ± 75 psi (16,545 ±517 kPa).
Right rear brake pressure ("RBP", 8) reads
2400 ± 75 psi (16,545 ±517 kPa).
Both pressures must remain above their mini-
mum values for a minimum of 20 seconds.
* Record on data sheet.
16. Release pedal, assure that each circuit's pressure
is zero.
17. Move the two 3000 psi (20,685 kPa) gauges to the
test ports on the front brake backplates.
J04025
18. Quickly and completely depress pedal. Verify that
within 1 second after brake is applied:
Left front brake pressure reads 2400 ± 75 psi
(16,545 ±517 kPa)
Right front brake pressure reads 2400 ± 75
psi (16,545 ±517 kPa).
Both pressures must remain above their mini-
mum values for a minimum of 20 seconds.
* Record on data sheet.
19. Release pedal, assure that each circuit's pressure
is zero.
20. Remove gauges from front brake test ports and
install at the "B1" and "B2" test ports in the hydrau-
lic cabinet.
21. Disconnect circuit #52B wire on the coil of the
brake lock solenoid (SV1) (14, Figure 4-1). Install
a jumper wire between circuits #33 and #33W at
the brake warning delay timer (27, Figure 4-1).
22. Apply the brake lock; the brake lock degradation
switch should close:
Verify the warning buzzer turns on.
Verify the low brake pressure warning lamp il-
luminates.
23. Depress the brake pedal until the warning stops.
24. Very slowly, release the brake pedal while ob-
serving the "B1" pressure gauge:
Verify warning resumes when pressure drops
to 1000 ±25 psi (6,895 ±172 kPa).
* Record pressure reading when alarm resumes.
25. Reconnect #52B wire at brake lock solenoid coil.
Remove jumper between circuits #33 and #33W.
26. Cycle brake lock several times to assure crisp shift
of solenoid valve and release of oil pressure.
Verify stop lights illuminate when brake lock is ON.
27. Apply brake lock and read brake pressure at "B1"
gauge:
Pressure should be 2000 ± 100 psi (13,788
±690 kPa).
* Record on data sheet.
28. If above pressure is not correct, remove plug on
end of PR valve (13, Figure 4-1) and adjust to
obtain correct pressure. Reinstall plug after ad-
justment.
Brake Circuit Checkout J4-5