BLEEDING THE HYDRAULIC SYSTEM

While some people claim that a hydraulic PAS system is self-bleeding, air in the system will be compressed by the high pressure generated as the steering wheel is turned, which can vary from 80 Bar to 140 Bar.

The air bubbles can damage the seals and pressure relief valves within the pump, so we recommend that the following procedure is carried out to bleed the system, to reduce the risk of any damage being done. 1 Raise both front wheels and secure the car body with axle stands. By relieving the wheels of weight, less hydraulic pressure is generated. 2 Check if your system has a PAS filter. This reservoir contains a magnetic plate to catch metallic contaminants, which can be removed, then the plate cleaned and refitted. 3 Fill the reservoir to the ‘Max’ mark. Turn the steering wheel from lock-tolock slowly, about 5-10 times, until no air bubbles emerge from the reservoir.

4 On cars with enginedriven pumps, disable the ignition and crank the starter motor for no more than 30 seconds, while moving the steering wheel back-and-forth.

5 Start the engine, checking that the fluid level does not fall too low. Turn the wheel lock-to-lock repeatedly 5-10 times. The fluid level should be steady.

6 If the fluid appears either frothy, or foamy, let the car stand for 15-30 minutes, so the bubbles can rise to the surface, before repeating the bleeding process.

7 Check that the cap is in good condition before refitting it. If present, the vent hole should not be blocked and its seal must be in good condition.