Bleeding The Hydraulic
System To Remove Air
This method of bleeding will take a few minutes longer than just filling the reservoir, running the engine at idle and allowing the system to self bleed. However it does ensure that most air is out of the system before starting the engine.
Hydraulic power steering pumps generate maximum pressures of between 1250psi (86bar) and 2000psi (138bar). Any air bubbles in the system when the steering is operated will be compressed by the fluid. These pressurised air bubbles being forced round the system can damage seals and can cause the pressure relief valves in the power steering pump to be jammed open, which will mean replacing the power steering pump. Raising the front wheels off the ground reduces the resistance to turning and so reduces the pressures in the system again helping reduce the effect of pressurised air bubbles.
- Raise the front wheels off the ground and disable the ignition.
- Fill the reservoir with steering fluid to the “MAX” mark.
- With the engine off slowly turn the steering wheel from side to side. Do not turn the wheel too rapidly or allow the pump reservoir to go below the “MIN” mark. Continue cycling the steering back and forth approx 5 – 10 until no more bubbles can be seen in the fluid reservoir and the reservoir level remains steady.
- Crank the engine on the starter motor several times while slowly cycling the steering back and forth. Again check for bubbles in the fluid reservoir and the reservoir level remains steady. Do not crank the engine for more than 20 seconds at a time to prevent damage to the starter.
- Finally, check the fluid level in the reservoir is at the “MAX” mark, start the vehicle and run at idle speed. Again slowly cycle the steering back and forth about 5 – 10 times. Ensure the pump reservoir does not go below the “MIN” mark. After cycling the steering there should be no bubbles in the fluid reservoir and the reservoir level should remain constant steady.
If there is still air in the system or the fluid appears foamy allow the vehicle to stand with the engine off for at least 15 minutes before starting the bleeding process again. After repeating the bleeding procedure if there is still air in the system look at our Tech Topic on frothy fluid.