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SERVICE MANUAL FOR SGR19 & SGR17
List of criteria for judging oil deterioration (Draw some oil out of the HST case into a test tube and
compare the sample with fresh oil.)
Appearance Smell Condition Countermeasure
Transparent and with no discolouration
Normal Good Keep on using as it is
Transparent but with small back dots
Normal Mixed with foreign matter Keep on using after filtering
Milky white Normal Mixed with water Replace with new oil
Blackened Bad Oxided and deteriorated Replace with new oil
4.11.TROUBLESHOOTING
When the HST unit is defective, it should be replaced with a new one as a rule. The following table will
assist you in understanding the HST system.
Trouble Presumable cause Countermeasure
The output shaft does not turn 1. Improper set pressure of relief Measure the pressure of low pressure
even when the control lever is valve in low pressure side circuit and replace defective parts
shifted either to α or β side. (Decreased pressure) if necessary.
2. Improper set pressure of relief Measure the pressure of high pressure
valve in high pressure side circuit and replace defective parts
(Decreased pressure) if necessary.
3. Broken charge pump (Decreased
Replace defective parts with new ones
.
charge flow)
4. Air is trapped within the HST Check suction piping of the charge
system. pump and oil level in the tank. (After
correction, bleed the HST system of
air.)
5. Erratic operation of the HST unit Wash the hydraulic circuit of the ma-
due to defective inner parts or chine thoroughly, repair the coupling
defective coupling of input or and replace the HST unit assembly
output shaft with a new one.
The output shaft does not stop 1. Erratic operation of the check Disassemble, wash it clean, and then
turning even when the control valve (Clogged choke) reassemble.
lever is shifted to the neutral
position. 2. Defective check valve seat Replace a defective seat with a new
one.
Low revolving speed of output 1. Highly pressurized oil is leaking Wash the hydraulic circuit of the ma-
shaft of the HST through worn frictioning parts chine thoroughly, replace the HST unit
of the pump or motor of the HST. assembly with a new one.
2. Air is trapped within the HST Check suction piping of the charge
system pump and oil level in the tank. (After
correction, bleed the HST system of
air.)
3. Decreased circuit flow caused Clean a clogged filter or strainer.
by a clogged filter or strainer
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