GILLIG LOW FLOOR, Руководство по обслуживанию

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Hydraulic System
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HyDRAULIC SySTEM COOLER
The hydraulic fluid cooler is integral to the radiator. To service the hydraulic fluid cooler, the whole ra -
diator assembly must be removed from the bus. Consult the “Radiator” section in the Engine chapter for
radiator removal instructions.Power Steering Hydraulic System Diagnosis
The power steering system is dependent upon adequate fluid pressure and flow to enable the steering
gear to operate as designed. Fluid pressure reacting on a piston creates the force to cause the piston to
move and assist the steering effort.
As the piston moves, it is displaced in the cylinder bore by a volume of fluid under pressure. How fast
the piston can be displaced is dependent upon adequate fluid flow and volume. Refer to the “Specifica -
tions” section of this manual for hydraulic pump specifications.
Back pressure and operating temperature must be considered during the diagnosis of power steering
problems. High back pressure will restrict movement of the piston in the steering gear. This back pres-
sure must be overcome before steering power is available. Back pressure is caused by restrictions to
fluid flow. Undersized replacement fittings and lines, pinched lines, and high flow rates are possible
causes of back pressure.
High system fluid temperatures reduce the overall efficiency of the pump and steering gear. High tem -
peratures are caused by restriction of flow or inadequate system fluid capacity to allow for heat dissipa -
tion during normal operation. A supply pump which constantly operates at maximum pressure relief will
also generate more heat than can be dissipated.
PRESSURE GAUGES AND TESTING
Various types of pressure gauges and flow meters are available and can be used to diagnose power steer -
ing problems. A pressure gauge which reads at least 3,000 psi (20,685 kPa) and a flow meter with a ca -
pacity of 10 gpm are needed to check pressures and flow. A shut-off valve downstream from the pressure
gauge makes it possible to isolate the hydraulic pump from the steering gear and, by closing the valve,
maximum pump relief pressure can be read.
A thermometer in the reservoir will indicate system fluid temperature.
The gauge set will indicate pressure (psi) and flow (gpm) with a single connection in series with the high
pressure line to the steering gear. A shut-off valve is included.