HOT OIL IN HYDRAULIC TANK
The temperature of the oil in the hydraulic tank is
If relief valve (6) is open, remove plug (7) and clean
controlled by the pump (1) for the oil through the oil
the valve and the seat in relief valve (6). Install a new
cooler and the oil cooler.
spring for the valve in relief valve (6) if necessary.
The pressure setting of the oil cooler relief valve is
30 + 3 psi (2.1 0.2 kg/cm2) with an oil flow of 10 U.S.
gpm (37.8 litre/min). There is no adjustment for the
pressure setting of the valve.
The location of the combination valve is below the floor
on the left side of the machine.
PUMP FOR OIL THROUGH THE OIL COOLER
1. Pump. 2. Line for oil leak from variable displacement
pump. 3. Line from variable displacement pump to the
hydraulic system. 4. Line from pump. 5. Line to tank.
6. Relief valve. 7. Plug. 8. Line to oil cooler. 9. Line
from oil cooler.
The normal temperature of the oil in the tank, when the
machine is operating, is 30 to 650 F (17 to 350 C)
1. Plug for valve stem and spring in unloader valve. 2.
more than the temperature of the atmosphere.
Plug for pressure reduction valve (steering). 3. Plug for
Causes for too much heat in oil tank:
1. Oil lines (8) and (9), to and from the oil cooler, have
When the oil from variable displacement pump
2. Relief valve (6) for oil cooler not closed.
goes through the combination valve and back to the
3. Too much dirt on oil cooler fins.
hydraulic tank, either the unloader valve or the relief
4. Oil passages in oil cooler not open (dirt in
valve or both valves are open. When either one of the
valves or both valves are open, the components in the
5. Pump (I) for oil cooler has damage (low output).
hydraulic system can not operate and the combination
6. The leak oil, in line (2) from the variable
valve needs cleaning, or an adjustment must be made.
displacement pump, is too hot. Too much leak oil,
because of damage in the variable displacement pump,
makes an increase in the temperature of the oil in line
(3). When the temperature of the oil in line (3) is 60 F
(33 C) more than the temperature of the oil in the tank,
the hot oil will not cool enough when the oil goes through
the oil cooler and into the hydraulic tank.
(Valve stem and spring removed)