Item name | Spare part number | Description |
1 | - | 4.0L V6 |
2 | - | 4.4L V8 |
3 | - | TdV6 |
Three different engine models use the same power steering pumps, however they have different connections and are therefore not interchangeable. A positive displacement vane pump generates hydraulic pressure in the steering control valve. The booster pump is driven by a V-ribbed belt from the crankshaft pulley. The pump speed increases in proportion to the engine speed. To maintain the required belt tension, a self-adjusting tensioner is used.
The pump has a built-in safety valve with a flow regulator for the working fluid.
Safety valve limits maximum steering pressure to 114 bar (1653 lbf inch2) ±4 bar (58 lbf inch2). The flow regulator limits the supply of working fluid to 8.8±0.5 l / min, regardless of the engine speed. The displacement of the pump is 9.6 cc/rev3.
The pump shaft is located longitudinally in the housing. A drive pulley is pressed onto one end of the shaft, and the opposite end of the shaft is closed with a cover. The shaft rotates in bearings mounted in the housing. Seals at both ends of the shaft prevent leakage of the working fluid.
The pump is equipped with an oval shaped hole in which ten blades rotate. The pump is driven by a shaft. Thanks to the shaped hole, when the blades rotate, the space between them increases. This causes a vacuum between the blades, due to which liquid from the tank is drawn into this space through the suction hose.
As the shaft rotates, the inlet of the blades, between which there is already liquid, closes, "locking" thus the liquid between the vanes. Thanks to the shaped hole, the space between the blades is reduced, which leads to compression of the liquid between them.
With further rotation of the shaft, the blades turn towards the outlet. As the vanes pass past the orifice, pressurized fluid flows from the pump outlet to the steering gear through the high pressure hose.
The supply of pressurized liquid is regulated by a safety valve with a flow regulator. The flow regulator provides a constant supply of working fluid to the steering mechanism, regardless of the engine speed. The safety valve regulates the pressure at the outlet of the pump. The pump outlet has a calibrated orifice. If the pressure in the calibrated port reaches a predetermined level, the spring-loaded ball in the center of the fluid flow regulator rises above its seat and allows the fluid to recirculate in the pump.
The safety valve is activated if the flow at the pump outlet is limited, for example, when the steering wheel is turned all the way. If the flow at the outlet of the pump is completely blocked, the liquid recirculates through the pump. Since there is no fresh fluid coming from the tank in this case, the temperature of the fluid in the pump rises rapidly. Thus, the duration of the operation of the steering mechanism in the extreme positions must be kept to a minimum in order to avoid overheating of the pump and the liquid in it.
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