Testing and Adjusting
During a diagnosis of the hydraulic system, remember that
correct oil flow and pressure are necessary for correct
operation. The output of the pump (oil flow) increases with an
increase in engine speed (rpm) and decreases when engine
speed (rpm) is decreased. Oil pressure is caused by
resistance to the flow of oil.
The 4C-4892 ORFS Fittings Group can be used to make the
pressure tests of the propel system. Before any tests are
made, visually inspect the complete hydraulic system for
leakage of oil and for parts that have damage. For some of the
tests a magnet, thermometer and a measuring rule (either for
inches or millimeters) are usable tools.
When any test is made of the system, the hydraulic oil must be
at the normal temperature for operation.
Sudden movement of the machine or release of oil under
pressure can cause injury to persons on or near the
machine. To prevent possible injury, do the procedure
that follows before testing and adjusting the propel
Move the machine to a smooth horizontal location.
Move away from working machines and personnel.
Permit only one operator on the machine. Keep all
other personnel either away from the machine or in view
of the operator.
Activate the parking brake.
Stop the engine.
Move the steering wheel to all positions to release any
pressure in the hydraulic system.
Carefully loosen the filler cap on the hydraulic tank to
release any pressure in the tank.
Make sure all hydraulic pressure is released before any
fitting, hose or component is loosened, tightened,
removed or adjusted.
The pressure in the system has now been released and
lines or components can be removed.
A visual inspection of the propel system and its components is
the first step when a diagnosis of a problem is made. Then
check the operation of the machine. Finally, check the system
with instruments. Stop the engine. To remove the tank filler
cap, slowly turn the filler cap until it is loose. Let the tank
pressure lower before the filler cap is removed. Make the
Measure the oil level of the hydraulic tank.
Look for air in the oil that is in the hydraulic tank. Do
this immediately after the machine is stopped. Use a
clear bottle or container to get a sample of the oil. Look
for air bubbles in the oil that is in the bottle.
Do not check for leaks with your hands. Pin hole (very
small) leaks can result in a high velocity oil stream that
will be invisible close to the hose. This oil can penetrate
the skin and cause personal injury. Use cardboard or
paper to locate pin hole leaks.
Inspect all oil lines and connections for damage or
leaks. Look for oil on the ground under the machine.
Remove the hydraulic filter elements and look for
particles removed from the oil by the filter elements. A
magnet will separate ferrous particles from nonferrous
particles (port plates, O-ring seals, etc.).
Bronze-colored particles give an indication of pump or
motor port plate failure.
Shiny steel particles give an indication of pump or
motor piston failure or motor cam deterioration.
Rubber particles give an indication of a seal or hose
Aluminum particles give an indication of steering
pump group failure.
Whenever foreign particles such as rubber or metal are found,
all the components of the propel, vibration, brake and steering
circuits must be flushed through. Each loop line circuit must be
independently filtered. Do not use parts that have been