Operation and maintenance manual

Section 250-0060
Braking System - Accumulator
SM 2160 7-02
2
WARNING
Hydraulic fluid pressure will remain
within the system after engine shut down.
Operate the treadle pedal continuously until the
pressure has dissipated before carrying out any
work on the braking system or serious injury
could result.
Testing Charging Valve For Leakage
Numbers in parentheses refer to Fig. 1.
1. Remove screws (2), lockwashers (3), protector (4)
and pads (11) from accumulator.
2. Remove cap (1A) from charging valve (1) and
loosen locknut (1D). Coat open end of charging valve
(1) with soapy water. Bubbles indicate leaky valve
core (1B).
3. Attempt to reseat the valve core by depressing and
releasing it quickly once or twice. Recheck for
leakage. If leakage continues, discharge the
accumulator as described under 'Discharging Nitrogen'
in this section.
4. Replace valve core (1B). Tighten locknut (1D) to
11 Nm (100 lbf in) and replace valve cap (1A) finger
tight.
Testing Precharge Pressure
Numbers in parentheses refer to Fig. 2, unless
otherwise specified.
Note: The nitrogen pressure in an accumulator is
directly affected by changes in nitrogen temperature.
The cylinder pressure will increase or decrease
proportionally with temperature changes. An
accumulator pressure reading can vary about 4.3 bar
(62 lbf/in²) with 22° C (72° F) temperature change.
Such temperature changes could easily occur
between noon and midnight of the same day. Refer to
the table at the end of this section for nitrogen
pressures at ambient temperatures of other than
21° C (70° F).
To test accumulator precharge pressure or to charge
the accumulator, a charging assembly kit can be used.
Refer to Fig. 2.
1. Position the vehicle in a level work area, apply the
parking brake, switch off the engine and turn steering
SM - 1273
wheel in both directions several times to relieve any
pressure in the steering circuit.
2. Operate the treadle valve continuously to relieve
pressure in the braking system. Block all road wheels
and place battery master switch in the 'Off' position.
3. Check accumulator mountings to be sure the
accumulator is held tightly in position.
4. Remove cap (1A, Fig. 1) from accumulator charging
valve (1, Fig. 1). Attach charging line (1) to charging
valve by rotating 'T' handle of valve chuck (2)
anticlockwise until it stops then screw the swivel nut
down on the valve. Loosen locknut (1D, Fig. 1) by
turning anticlockwise one to two turns.
5. Turn 'T' handle clockwise until charging valve core
is depressed. Be sure bleeder valve (10) is tight and
does not leak, and valves (4 & 6) are closed.
6. To read accumulator precharge pressure, slowly
open cylinder valve (4). Pressure gauge (5) will
register precharge pressure, it should be 55 bar
(800 lbf/in²) at 21° C (70° F) ambient temperature.
Refer to the table at the end of this section for nitrogen
pressures at ambient temperatures of other than 21° C
(70° F).
1 - Line
2 - Valve Chuck
3 - Valve Extension
4 - Cylinder Valve
5 - Pressure Gauge
6- Tank Valve
7 - Gland Fitting
8 - Gland Nut
9 - Cylinder Adaptor
10 - Bleeder Valve
Fig. 2 - Charging Assembly Kit