JLG 600SC_660SJC Service Manual - Manual (Page 114)

SECTION 5 - CAT CHASSIS (S/N 0300128000 TO PRESENT)
5-22 – JLG Lift – 3121157
Troubleshooting for Parking Brake
Troubleshooting for High Pressure Relief Valve
TROUBLES (TYPE OF FAILURE) POSSIBLE CAUSES CORRECTIVE ACTIONS
Shortage of braking force or one-sided
braking Brake disk is worn. Replace the worn disk with new one. Remove foreign
substances thoroughly, repair damaged parts, and
reassemble them after cleaning.
Deterioration or poor contact of disk surfaces Polish and correct the surface. Clean it before reas-
sembly. If it is too much degraded, replace it with new
one.
Worn or damaged springs Replace the spring with new one. Remove foreign
substances thoroughly, and clean it before reassem-
bly.
The bolt for manually releasing brake is mounted. Remove the bolt for manually releasing brake, and
install a blind plug.
Pilot pressure for releasing brake is in operation. Check to see if pressurized oil in the pilot for releasing
brake is ON or OFF, and then, provide each equipment
with necessary inspection and maintenance.
Abnormal heating due to brake dragging Brake release failure:
1) Oil leakage due to O-ring breakage
2) Clogged orifice
3) Pressurized oil in the pilot for releasing brake is not
in operation.
4) Pilot pressure for releasing brake is low. - Replace the damaged O-ring with new one.
- Wash the orifice before reassembly.
- Check to see if the pilot port is pressurized or not, and
provide equipment with necessary inspection and
maintenance.
Parking brake cannot be manually
released. Tightening of bolts for manual release is uneven. Tighten the bolts evenly.
TROUBLES (TYPE OF FAILURE) POSSIBLE CAUSES CORRECTIVE ACTIONS
Motor does not rotate or rotates slowly. Relief valve receipt malfunctions;
1) Foreign articles are jammed in.
2) Spring is broken. - Remove foreign articles thoroughly. Repair damaged
parts, and reassemble the parts after cleanup. If deep
scratches or more than normal wear are found on the
parts, the parts should be replaced with new ones.
- Replace spring with new one. Then, remove foreign
articles thoroughly.
Cracking pressure of the relief valve is lowered;
1) Spring wear-out
2) Clogged poppet orifice - Replace relief valve sub assembly with new one.
- Wash and clean the clogged orifice prior to reassem-
bly.
2. Motor does not stop or stops slowly. Relief valve receipt malfunctions;
1) Foreign articles are jammed in.
2) Spring is broken. - Remove foreign articles thoroughly. Repair damaged
parts, and reassemble the parts after cleanup. If deep
scratches or more than normal wear are found on the
parts, the parts should be replaced with new ones.
- Replace spring with new one.
Cracking pressure of the relief valve is lowered;
1) Spring wear-out
2) Clogged poppet orifice - Replace relief valve sub assembly with new one.
- Wash and clean the clogged orifice prior to reassem-
bly.