Service Manual User Manual

Hydraulic System
9-5
Figure 9–4. Flowmeter hydraulic diagnostic kit.
9.3.1 Pressure Checks and Adjustments
When diagnosing trouble in the hydraulic system, use the
hydraulic testing information on the pages 9-6 and 9-7.
Note: Duplicate pages have been provided on pages 9-8
through 9-11 in the event the technician needs the infor-
mation for field use or to laminate and store elsewhere.
Keep in mind that what may at first seem to be a hydrau-
lic problem could actually be a mechanical or electrical
problem. The true cause of the trouble must be diag-
nosed and cured, or the problem will recur.
The following specifications are important to consider
when conducting pressure checks and adjustments:
• In the boom hoist/lower cylinder, the
counterbalance valve in the base end of the
cylinder is rated at 4000 psi (276 bar).
• The pop-off emergency relief valve port relief built
into the working section of the main control valve is
rated at 3750 psi (258,75 bar).
• If system pressure exceeds 3500 psi (241,5 bar),
the main relief valve will open, allowing oil to return
to the reservoir.
• If the return filter becomes plugged, hydraulic oil will
bypass the filter when pressure reaches 25 psi
(1,725 bar).
In general, follow the steps below whenever conducting
pressure checks and performing adjustments:
1. Park the vehicle on a firm, level surface. Engage the
park brake, place the travel select lever in NEUTRAL
(N), level the boom and turn the engine OFF.
2. Pressure tee fittings are conveniently located in each
hydraulic circuit. Install a pressure gauge capable of
measuring at least 10% more pressure than that
which the circuit being checked operates under.
If the vehicle is equipped with optional auxiliary
hydraulics, relieve pressure by pulling the manually-
operated release valve handle (Fig. 9–2).
3. Start the engine. Operate vehicle functions several
times to allow hydraulic oil to reach operating
temperature. The hydraulic oil temperature should be
between 100 and 120° F (38 and 49° C). If a
temperature gauge or thermometer is unavailable,
the hydraulic oil reservoir should be warm to the
touch.
4. Refer to Pressure Test Procedures on page 9-7.
5. Fully depress the accelerator pedal as required.
Place and hold the joystick in the position needed to
operate the particular vehicle function being checked.
Continue holding the joystick in position until
pressure readings are taken.
6. Check the pressure gauge reading. It should read as
specified in the Pressure Readings column on page
9-7. If the reading is not as specified, turn the engine
OFF and check other components in the system.
Verify that all related hydraulic components and
electrical switches, sensors, solenoids, etc. are
operating correctly.
7. As a last resort, adjust the appropriate relief valve, if
applicable. Turning the adjustment screw clockwise
will increase the pressure; turning the screw
counterclockwise will decrease the pressure
8. Start the engine and check the pressure again. Turn
the engine OFF, pull the manually-operated release
valve handle on units equipped with the optional
auxiliary hydraulic system, then disconnect or
remove the pressure gauge from the vehicle.
MS2120
MS2130
WARNING: Avoid prolonged engine operation
in closed areas with inadequate ventilation.
Failure to properly ventilate exhaust fumes can
result in death or severe personal injury.
WARNING: Avoid prolonged engine operation
in closed areas with inadequate ventilation.
Failure to properly ventilate exhaust fumes can
result in death or severe personal injury.
Model 3606 • Origin 10/99