How To Get Air Out Of Power Steering: The Complete Bleeding Guide

Trapped air inside a hydraulic power steering system creates a spongy pedal or steering wheel feel, loud whining noises, and erratic resistance during low-speed maneuvers. Purging this air requires raising the front end of the vehicle, cycling the steering wheel lock-to-lock with the engine off and on, and maintaining strict fluid levels using manufacturer-specified hydraulic oil.

Pre-Procedure Planning and Tool Requirements

Eliminating air pockets from a hydraulic steering circuit demands methodical preparation to prevent pump cavitation and premature component wear. When air mixes with power steering fluid, it forms a compressible froth that prevents consistent pressure delivery from the rotary vane or roller pump to the steering rack or steering gear box. Before starting, ensure the vehicle is parked on a flat, level surface and verify that the parking brake is fully engaged.

• Essential Gear, Tools, and Materials:
  
  
  • Hydraulic floor jack and two rated jack stands
  • Wheel chocks
  • Manufacturer-specified power steering fluid (e.g., ATF Type DEXRON III/VI, specific CHF synthetic mineral oils, or Honda-specific formulations depending on the make)
  • Large turkey baster or fluid suction syringe
  • Clean lint-free shop rags
  • Long-handled funnel
  • Safety glasses and mechanic gloves
• Prerequisite Knowledge and Standards:
  
  
  • Never run the power steering pump dry or hold the steering wheel at full lock for more than 5 to 10 seconds, as this generates extreme internal heat and damages the pump housing and flow control valve.
  • Inspect all high-pressure lines, return hoses, and hose clamps for weeping or loose connections before attempting to bleed the system.
• Duration and Budget:
  
  
  • Estimated Time: 30 to 45 minutes
  • Estimated Cost: 10 to 30 dollars for fresh fluid if a complete flush is required.

Step-by-Step Power Steering Bleeding Workflow

Step 1: Elevate and Secure the Front End

Position your floor jack under the manufacturer-approved front crossmember or subframe lift point. Raise the front of the vehicle until both front tires are completely off the ground by at least two to three inches. Lower the vehicle securely onto rated jack stands placed beneath the pinch welds or frame rails. Place wheel chocks tightly against both sides of the rear tires to prevent any longitudinal movement during the procedure.

Step 2: Inspect and Evacuate the Reservoir

Pop the hood and locate the power steering fluid reservoir. Wipe away any accumulated dirt, road grime, or oil around the cap to prevent contamination. Remove the cap and inspect the fluid condition. If the fluid appears foamy, milky brown, or dark black, use a turkey baster or fluid extractor to suck out the old, aerated fluid from the reservoir. Refill the reservoir up to the "Cold Max" line using fresh, clean fluid that strictly matches your vehicle owner manual specifications.

Step 3: Perform Dry Lock-to-Lock Cycling

With the engine completely turned off, climb inside the vehicle and slowly rotate the steering wheel all the way to the far left lock until it gently hits its internal stop, then smoothly rotate it all the way to the far right lock. Repeat this full-lock cycle 10 to 15 times. This manual steering rack movement acts as a manual displacement pump, forcing trapped air bubbles up through the return line and out into the fluid reservoir.

Pro-Tip: Watch the fluid reservoir while an assistant cycles the steering wheel, or check it yourself every five cycles. As air escapes, you will see tiny bubbles rising to the surface and fluid levels dropping rapidly. Always top off the reservoir before the level drops low enough to draw fresh air back into the pump inlet.

Step 4: Check Fluid and Monitor Aeration

Top off the reservoir back to the designated fill line. Leave the reservoir cap off or loosely resting on top to allow trapped vapor to escape freely. Start the engine and let it idle for approximately 5 to 10 seconds, then immediately shut it off. Observe the fluid inside the reservoir for vigorous foaming or bubbling. If the fluid turned into a frothy milkshake, wait 10 to 15 minutes for the micro-bubbles to dissipate before proceeding.

Step 5: Wet Cycling with Engine Running

Start the engine and let it idle continuously. While the engine runs, slowly turn the steering wheel from lock to lock another 5 to 8 times. Keep movements smooth and continuous, pausing for one full second before hitting each hard stop. Listen closely to the pump; the loud groaning or whining noise should steadily diminish and vanish as the remaining air is purged through the system and displaced by dense hydraulic fluid.

Step 6: Final Verification and Road Testing

Turn off the engine, wipe down any spilled fluid, and top off the reservoir one final time to the exact "Hot" or "Cold" operating level indicator. Secure the reservoir cap tightly. Lower the vehicle back down to the ground using the floor jack. Start the engine and perform a final lock-to-lock check while stationary, ensuring the steering wheel feels uniformly light, responsive, and quiet. Take the vehicle for a brief, low-speed test drive around your neighborhood to confirm proper return-to-center action and complete elimination of hydraulic noise.

Power Steering Fluid Specifications and System Methods

Common System Failures and Field Fixes

Even with meticulous execution, certain mechanical faults can mimic trapped air or prevent complete system bleeding. Review these real-world failure scenarios to isolate persistent steering issues.

• Persistent Whining and Foaming After Multiple Bleed Attempts:
  
  
  • Root Cause: A micro-tear or loose worm-gear clamp on the low-pressure suction hose running from the reservoir to the pump inlet. When the pump operates, it draws ambient air straight past the loose joint instead of drawing fluid, continuously re-introducing air into the hydraulic circuit.
  • Actionable Fix: Replace the spring-type constant-tension clamp with a heavy-duty screw-type hose clamp, or replace the entire low-pressure rubber suction hose if the rubber has hardened or cracked.
• Stiff Steering Spots Despite Zero Bubbles in Reservoir:
  
  
  • Root Cause: Internal corrosion, mechanical binding within the universal joints of the intermediate steering shaft, or a collapsing inner lining of the high-pressure line.
  • Actionable Fix: Disconnect the intermediate shaft and check for binding in the U-joints; inspect the pressure hose for internal restrictions or kinks that choke hydraulic flow.
• Sudden Fluid Expulsion Out of Reservoir Vent Cap:
  
  
  • Root Cause: Overfilling the reservoir combined with severe cavitation, or introducing water/moisture contamination into the fluid.
  • Actionable Fix: Extract the contaminated fluid completely, flush the entire system with fresh manufacturer-approved fluid, and refill precisely to the cold level line.

Frequently Asked Questions

Can I drive my car with air trapped in the power steering system?

Driving with air trapped in the system is strongly discouraged. The lack of proper hydraulic cushioning causes extreme stress on the power steering pump vanes, leading to catastrophic pump failure, metal particle contamination, and sudden loss of steering assist.

Why does my power steering reservoir keep foaming?

Foaming occurs when the pump draws in air through a suction-side leak or when low fluid levels allow the pump inlet to vortex and pull air into the fluid. Letting the vehicle sit allows the micro-bubbles to aggregate and rise so you can identify and seal the air leak.

Do all power steering systems use automatic transmission fluid?

No. While many American and Asian vehicles utilize standard Automatic Transmission Fluid, many European manufacturers like BMW, Audi, Volkswagen, and Porsche require specialized hydraulic mineral oils such as Pentosin. Always check your owner manual before adding any fluid.

How do I know if my power steering pump is ruined?

If you have successfully purged all air and verified correct fluid levels, but the pump continues to produce a loud metallic squeal, lacks assist entirely, or contains metallic flakes in the reservoir, the internal pump housing and flow valve are likely damaged and require replacement.

Maintain peak vehicle handling and eliminate hydraulic noise by using the correct fluids and following precise bleeding protocols during every service interval.