Komatsu 830E-AC Shop Manual page 589

BRAKE CIRCUIT AND BRAKE VALVE TROUBLESHOOTING
POSSIBLE CAUSES
TROUBLE: The Brakes are Locked, Service and/or Parking
Parking brake solenoid is de-energized.
Connections to tank and pressure ports reversed.
Parking brake solenoid coil defective.
Parking brake solenoid valve defective.
Tank line is plugged or restricted.
TROUBLE: Both Brake Circuits are Dragging
Tank line has back pressure.
Pedal set screw out of adjustment; residual pres-
sure.
TROUBLE: One Brake Circuit is Dragging
Obstruction in the brake valve subassembly.
Brake valve is out of balance.
Actuator piston defective.
Brake valve is defective.
TROUBLE: The Brakes are Not Going to Full Pressure
Internal malfunction of modulating section of Brake
Valve.
Supply pressure is low.
Improper collar adjustment inside brake valve.
TROUBLE: A Brake Accumulator Bleeds Off Quickly When Supply Pressure is Cut Off
Accumulator bleeddown valve is open.
Accumulator precharge is low.
Leak in one circuit.
Malfunction in brake valve.
J04036
SUGGESTED CORRECTIVE ACTION
Check power to solenoid
Correct the plumbing.
Replace coil.
Replace solenoid valve.
Remove restriction.
Ensure tank line has no back pressure.
Adjust pedal dead band with set screw.
Remove obstruction.
Adjust balance according to instructions.
Replace piston.
Rebuild or replace Brake Valve assembly.
Remove, disassemble, clean, and inspect brake
valve.
Check steering/brake pump system and accumula-
tors.
Adjust collars according to instructions.
Close valve, check precharge.
Recharge accumulator.
Check plumbing.
Remove, disassemble, clean, reassemble; or
replace.
Brake Circuit Check-Out Procedure J4-9