Power Steering Pump: Description and Operation

DESCRIPTION
The hydraulic servo pump is driven by a multi-V belt from the crankshaft pulley.
The pump incorporates a control valve for regulation of the pressure and flow and also an overflow valve.

WARNING: To avoid damage to the pump the following points should be observed:
1. Never forcibly hold the steering wheel at full lock for any length of time with the engine running, as this may cause the pump to overheat and be damaged.
2. Take great care to prevent any particles of dirt from entering the hydraulic system, e.g. when checking or topping up the fluid level.
3. Never allow the pump to run dry, with no fluid in the system.





PRINCIPLE OF OPERATION
The pump consists of a rotor (No. 1, as shown) containing a number of slots, a vane (No. 2, as shown) for each slot, a pump casing (No. 3, as shown), and two end plates (No. 4, as shown) with inlet and outlet ports for the hydraulic fluid.
Due to the oval shape of the pump casing, the volume between the vanes increases and decreases twice during each revolution of the rotor. Inlet ports lead to the areas in which the volume increases and outlet ports from those in which the volume decreases, thereby producing a pumping effect. Apart from being forced out by centrifugal force, the vanes are also pressed outwards against the pump casing by the pressure of the fluid flowing through the slots at the bottom of the vanes.