Propulsion System; Machine Moves Neither Forward Nor Backward 1/2 - Sakai R2-4 Shop Manual

3-2. Propulsion System

If a problem occurs in the propulsion systems such as the propulsion pump, propulsion motor and brakes,
determine the cause and carry out action as required, according to the following general troubleshooting items.
(NOTICE)
• When checking whether or not the pressure is correct, refer to the pressure standard value for each
hydraulic circuit.

3-2-1. Machine moves neither forward nor backward 1/2

Check point
1. Oil Level of
Hydraulic Oil Tank
2. Bypass Valve
3. F-R Lever Linkage
4. Charge Circuit
Pressure
5. Plopulsion Pump
Neutral Solenoid
Valve
6. Suction Filter for
Steering • Charge
Pump
7. Propulsion Circuit
Pressure
8. Propulsion Motor
Cause
Oil level in hydraulic oil tank is low.
Bypass valve is open.
F-R lever linkage is faulty.
Propulsion pump does not discharge oil
because charge pressure is low.
Insufficient steering • charge pump
discharge.
Charge pressure decreases due to internal
leakage of solenoid valve connecting oil
supply circuit with charge circuit.
• Parking brake solenoid valve
• Speed change solenoid valve
Swash plate is not switched from neutral
position because spool of plopulsion pump
neutral solenoid valve is stuck.
Steering • charge pump flow is reduced due
to clogged filter.
Circuit does not obtain required pressure
because setting pressure of high pressure
relief is low.
Propulsion circuit pressure is not held in
propulsion motor case.
Internal leakage of propulsion motor.
Sticking of brake discs causes brakes to
remain applied.
TROUBLESHOOTING
Check/Action
Fill tank until correct oil level is obtained.
Close bypass valve.
Check and adjust F-R lever linkage or
replace it if necessary.
• Measure charge pressure.
• If low, check and adjust charge relief valve
or replace it if necessary.
Repair steering • charge pump or replace it
if necessary.
• When solenoid is energized, check if oil
flows in return circuit to tank.
• If oil is flowing, repair solenoid valve or
replace it if necessary.
If valve spool does not move, repair or
replace plopulsion pump neutral solenoid
valve.
Clean suction filter or replace it if necessary.
• Measure propulsion circuit pressure.
• If low, check and adjust multifunction valve
or replace it if necessary.
If pressure in propulsion motor case is not
within allowable range, repair propulsion
motor or replace it if necessary.
• Measure drain quantity from propulsion
motor.
• If drain quantity is larger than standard
value, repair propulsion motor or replace it
if necessary.
Replace brake discs.
10-067