Bleeding a hydraulic power steering system: symptoms, steps and checks

When bleeding is needed

• After fitting a rack, pump, hose or reservoir.
• After the level dropped below minimum or the reservoir ran dry.
• When the pump whines continuously and the reservoir foams.
• When steering feels heavy or uneven after a fluid change.

Read the symptoms first

Standard steps

• Park on level ground, raise the front wheels, apply the handbrake or chocks.
• Engine off; fill the reservoir to the upper mark (cold level per manual).
• Turn slowly from lock to lock, pausing only briefly at each stop; repeat and top up as the level drops.
• Start the engine at idle and repeat the lock-to-lock turns while watching level and foam.
• Switch off, let the foam settle, then top up to the specified level.
• Road test slowly through left and right bends; recheck level and leaks back in the workshop.

Whether vacuum bleeding is required and how many turns to make depends on the model manual; some vehicles need dedicated equipment.

How to tell it is done

• No foam on the fluid surface, and none rising after standing.
• Level stable, no longer dropping.
• No continuous pump noise and even assist left to right.
• No shudder when turning, normal noise at full lock.

Common mistakes

• Continuing to turn the wheel after the reservoir has run dry, so the pump runs dry.
• Holding the wheel at full lock for a long time.
• Using the wrong fluid, or mixing different specifications.
• Topping up without bleeding, so the foam stays.
• Ignoring a suction hose leak, so air returns after bleeding.

EPS has no hydraulic fluid; do not follow this procedure on an electric rack.