21 - 1
Flow and Pressure Testing
Main Pump
The main hydraulic pump is mounted on the left side of the
engine and driven from the power take off point below the
injector pump. The unit supplies hydraulic fluid to the
machine's main services circuit and also to the steering
circuit via the priority valve.
If a hydraulic fault is suspected, check flow and pressure of
the pump and the operation of the priority valve before
removing and dismantling the unit.
As a pre-requisit to checking the flow and pressure of the
pump, it is necessary to check the setting of the main relief
valve (MRV), refer to Pressure Testing - MRV. Adjust if
necessary.
!!
WARNING
Hydraulic fluid at system pressure can injure you. Before
disconnecting or connecting hydraulic hoses, stop the
engine and operate the controls to release pressure
trapped in the hoses. Make sure the engine cannot be
started while the hoses are open.
INT-3-1-11/1
!!
WARNING
Take care when disconnecting hydraulic hoses and
fittings as the oil will be HOT.
TRANS 1-2
1 Switch off the engine and remove the starter key.
2 Relieve residual system pressure by operating the
services controls a few times.
3 Disconnect the pump outlet hose A. Connect a flow
meter (service tool 892/00268) and load valve (service
tool 892/00270) in the line between the pump outlet
port and the hose.
Note: Make sure the flow meter is installed with its arrow
pointing away from the pump. Make sure the load valve is in
the open position, i.e. with the adjusting knob screwed fully
out.
4 Connect a 0-400 bar (0-6000 lbf/in
2
) pressure gauge to
the load valve pressure test point.
5 Start the engine and bring the hydraulics up to working
temperature 50ºC (122ºF). Set the engine speed to
2000 rpm.
6 Carefully adjust the load valve to steadily increase the
pressure so that the pressure gauge reads just below
the MRV setting.
7 Observe the pressure and flow readings achieved,
these should be as given in Technical Data.
Section E Hydraulics
9803/7130
Section E
21 - 1
Issue 1
Service Procedures
AA
A230520
8 If the flow is less than that specified replace the pump
complete. DO NOT individually renew the gears or the
housing as this will not effect a permanent cure.
9 When testing is complete repeat steps 1 and 2. Remove
the flow meter, load valve and the pressure gauge from
the line. Reconnect the pump outlet hose A.
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