3. TROUBLESHOOTING

Problem Symptom

* Forward/reverse driving is not available

* Forward/reverse driving is not available

* Insufficient power when forward/reverse driving

* Delayed response

* Noise in HST operation

* Max. speed is not achievable

PTO shaft does not rotate

Insufficient transmission fluid

Dirty or discolored transmission fluid

Possible cause

Action

If it does not rotate, the input shaft is damaged. Repair the input shaft.

If the fluid is insufficient, the charge oil is not supplied sufficiently. Replenish oil.

The viscosity is too high or too low due to the aged or dirty fluid.

Change the fluid

Cannot keep neutral position

(The tractor moves slightly when in neutral)

Power loss due to overheated oil

There are bubbles in fluid. Repair the inlet line of gear pump. Abnormal condition of HST pedal link

Low charge pressure (standard: 4 ~ 6 kg/cm2 (57 ~ 85 psi))

The link is damaged, loose or displaced.

The charge oil is insufficient due to the clogged oil filter.

Repair the related parts.

Replace the filter.

The charge relief valve is damaged. Replace the charge relief valve.

The hydraulic line related to the 2nd gear pump is defective.

Repair the related parts. Refer to the "Hydraulic system" in this manual.

Too low pressure in high pressure relief valve for forward/reverse driving (standard: 300 kg/cm2 (4,266 psi))

Improperly adjusted HST pedal link, defective link

The relief valve is defective. (Especially, only one of two valves is defective.)

Replace the relief valve.

The HST plate is excessively worn. Replace the plate. The HST cylinder block and the piston are excessively worn. Replace the HST.

It is in neutral when the link is disconnected and the wheels are off from the ground.

Adjust and repair the link.

Check the oil cooler

Check the oil

The air passage of the cooler is blocked. Clean it.

Improper, aged or dirty oil Change the oil.

Check the HST valves The valve springs and spool are stuck. Clean the valves, replace the springs and replace the whole vales. Oil leakage

Check the leaking area Check the oil seal, gasket and pipe O-ring. Repair or replace as necessary.

Excessively raised charge pressure

Check if the HST filter is clogged. Replace the filter. Replace the charge relief valve.

4. MEASUREMENT AND ADJUSTMENT

Measure the relief valve pressure to check if the damage in the HST is due to the worn internal parts or the relief valve itself and then to determine if replacing or repairing the HST is necessary.

4.1 CHARGE RELIEF VALVE PRESSURE CHECK

5. Place the HST pedal in the neutral position and measure the pressure in the specified test condition.

• Test condition

Engine rpm .................... 2,600 rpm

T��������������� 50 ~ 60°C

Charge relief setting pressure ............ 0.39 ~ 0.59 MPa

4 ~ 6 kgf/cm2

57 ~ 85 psi

6. If the measured charge relief valve pressure is below the specification, check for blocking of the HST filter, blocking of the oil filter in front of the hydraulic pump, malfunction of hydraulic pump (#1) and related hydraulic lines and blocking of the oil cooler.

Warning

• Perform the test in a open and broad area. The tractor may move unexpectedly and cause an accident.

• Never let anyone other than the driver get near the front and rear side of the tractor. Any observer can be hit by a tractor during the test and he/she can seriously get injured.

Caution

• Check the transmission ���level with the dipstick before the test and replenish the ���if necessary. If the ���is ������� it can cause damage in the HST.

1. Unscrew the HST mounting plate mounting bolt (1) from the bottom of the tractor's left step as shown in the figure.

2. Unscrew the pressure relief plug (2) from the HST mounting plate and install the adapter (PF 1/4) for pressure gauge installation.

3. Connect the pressure gauge (50 kgf/cm2 or higher).

4. Start the engine and warm up the engine until the hydraulic fluid gets warm properly

Warning

• Be extra careful not to sharply depress the HST pedal. If it is abruptly depressed, it can cause an accident.