How to Remove Air Bubbles from Power Steering Fluid

To get air out of your power steering fluid, safely raise the front wheels, top up the correct fluid, and with the engine off turn the steering wheel slowly from lock to lock 20–30 times to purge air into the reservoir; let it de-aerate, then start the engine and repeat until the fluid runs clear and quiet. For stubborn foaming, apply a hand vacuum pump at the reservoir to draw 20–25 inHg while cycling the wheel. If bubbles persist, check for suction-side leaks and worn seals.

Why Air Gets In—and Why It Matters

Air enters hydraulic power steering when the fluid level is low, hoses or O-rings leak on the pump’s suction side, or after component replacement. Aerated fluid compresses under pressure, causing noise, heavy or jerky steering, and accelerated wear of the pump and rack. The goal of bleeding is to move trapped air to the reservoir and let it escape without cavitating the pump.

Symptoms and Causes

Before you begin, it helps to confirm you’re actually dealing with aeration and to understand likely sources. These quick checks can save time and prevent repeat issues.

• Whining or groaning from the pump, especially on cold start or during turns
• Foamy, milky, or bubbly fluid visible in the reservoir
• Intermittent heavy steering or vibration in the wheel
• Fluid level that rises and falls as bubbles move through the system

If you notice several of these symptoms together, air in the system is likely, and bleeding will often restore normal operation.

Air usually finds its way in through specific weak points. Knowing the common culprits helps you fix the root cause, not just the symptom.

• Low fluid level drawing air into the pump inlet
• Loose clamps or cracked rubber on the low-pressure return or pump suction hose
• Hardened or flattened O-ring at the pump inlet fitting
• Turbulence from fluid returning too close to the pickup in the reservoir
• After service: pump, hose, or rack replacement without proper bleed procedure

If aeration returns soon after bleeding, inspect these areas closely; persistent foaming almost always indicates a suction-side issue rather than a high-pressure leak.

Preparation and What You’ll Need

Set up safely and gather the right materials so the bleed proceeds smoothly and without introducing new contamination.

• Vehicle owner’s manual or service manual (to confirm fluid spec and any model-specific steps)
• Correct power steering fluid or specified ATF (e.g., CHF 11S/202 on some European cars; do not mix types)
• Floor jack and jack stands (or a lift) to raise the front wheels
• Clean rags, catch pan, and a funnel with a fine screen
• Hand vacuum pump with reservoir adapter (for vacuum bleeding)
• Safety gear: gloves and eye protection

Work on a cool engine in a well-ventilated area. Keep belts and pulleys clear. Clean the reservoir cap area before opening to avoid introducing debris.

Step-by-Step: Manual Bleeding (Most Vehicles)

This standard method uses the steering rack’s motion to move air to the reservoir without cavitating the pump. It is suitable after fluid changes or minor air ingestion.

1. Raise the front of the vehicle and support it securely so the front wheels are off the ground.
2. Clean around the reservoir cap. Remove the cap and check fluid level and condition. Top up with the specified fluid to the COLD mark.
3. With the engine OFF, slowly turn the steering wheel from full left lock to full right lock 20–30 times. Do not hold at either lock; pause just as the wheel reaches the stop.
4. Watch the reservoir. Add fluid as the level drops and allow foam to dissipate between cycles. Avoid letting the pickup uncover.
5. Let the vehicle sit 5–10 minutes to allow microbubbles to separate in the reservoir.
6. Start the engine and let it idle. Slowly turn the wheel lock-to-lock 10–15 more times. Do not hold at full lock for more than 5 seconds.
7. Monitor the reservoir for clear, non-foamy fluid. Top to the HOT/operating range if the fluid has warmed; otherwise, leave at COLD and recheck after a short drive.
8. Lower the vehicle, road test with gentle steering inputs, then recheck level and look for leaks.

When done correctly, the pump noise should fade, steering feel should normalize, and the reservoir should show clear fluid without foam. If not, repeat the cycle once more or proceed to vacuum bleeding.

Vacuum Bleeding for Stubborn Aeration

Vacuum bleeding helps pull dissolved air out of the fluid and draws trapped bubbles out of the rack and lines. It is particularly effective after major component replacement or when a pump continues to whine.

1. Install a suitable vacuum adapter on the reservoir opening to create an airtight seal.
2. With the engine OFF, use a hand vacuum pump to pull 20–25 inHg on the reservoir. Maintain vacuum for 3–5 minutes.
3. While holding vacuum, slowly turn the steering wheel side to side (do not reach the stops). You may see bubbles rise through the return flow.
4. Release vacuum slowly to prevent fluid from foaming up. Top off fluid as needed.
5. Repeat the vacuum-and-cycle process 1–2 times, then start the engine and perform slow lock-to-lock turns for final de-aeration.

Vacuum bleeding accelerates air removal without stressing the pump. If bubbles continue after two cycles, investigate for air ingress on the suction side.

After the Bleed: Checks and Adjustments

Once steering is quiet and smooth, verify that the system is tight and fluid is at the correct level and spec.

• Confirm fluid level at the appropriate HOT or COLD mark per the dipstick/reservoir.
• Inspect the pump inlet hose and clamps; replace any soft, cracked, or oil-saturated rubber.
• Look for wetness around the pump shaft seal and rack boots indicating leaks.
• Ensure the reservoir screen (if equipped) is clean and the return jet isn’t aimed at the pickup.
• Avoid additives unless explicitly approved by the manufacturer; many can change fluid aeration characteristics.

These final checks reduce the chance of recurring foam, protect the pump, and keep steering effort consistent.

If Bubbles Keep Returning

Persistent aeration points to a root cause that bleeding alone won’t fix. Focus on the suction side and components that see vacuum rather than pressure.

• Hardened O-ring at pump inlet: a common, inexpensive fix—replace with the exact size and material.
• Loose or undersized clamps on the low-pressure hoses: use proper fuel-injection–style clamps, not worm clamps that can ovalize fittings.
• Microcracks in the reservoir neck or hose barb: replace the reservoir if any doubt.
• Return flow turbulence in aftermarket or incorrect reservoirs: fit the correct OE-style reservoir with internal baffles.
• Internal rack leaks that aerate fluid: look for fluid in rack boots; rebuild or replace as needed.

Diagnosing and correcting these faults will stop air from re-entering, ensuring the bleed holds over time.

Prevention and Best Practices

Good habits minimize aeration risk and extend system life, especially on high-mileage vehicles or those operated in extreme temperatures.

• Use only the fluid specified by your manufacturer; many systems are sensitive to viscosity and anti-foam additives.
• Never run the reservoir low or the pump dry; top off promptly after repairs.
• Do not hold the wheel at full lock for more than 5 seconds—this overheats fluid and stresses the pump.
• Flush old, dark, or contaminated fluid; fresh fluid resists foaming better.
• Inspect hoses and clamps annually; replace aging rubber proactively.

Following these practices helps keep your steering quiet, responsive, and reliable while avoiding premature pump or rack failure.

Note on Electric Power Steering (EPS)

Many newer vehicles use fully electric power steering with no hydraulic fluid to bleed. If your vehicle has EPS, aerated fluid is not applicable. Some models use electro-hydraulic systems (EHPS) with a fluid reservoir and electric pump—the above procedures still apply, but always follow the service manual for system-specific steps.

Summary

Raise the front wheels, top up the correct fluid, and purge air by slowly turning the wheel lock-to-lock with the engine off, then on, until the reservoir shows clear, foam-free fluid. A vacuum pump at the reservoir speeds de-aeration. If bubbles persist, fix suction-side leaks (hoses, clamps, pump inlet O-ring) and verify you’re using the specified fluid. Proper bleeding and minor repairs typically restore quiet, smooth steering and protect the system from damage.

How to get air out of power steering without a vacuum pump?

You remove the lid of the fluid reservoir, top up the fluid, and turn the steering wheel from lock to lock a few times. This should remove the air from the system. The you top up the fluid again – if it needs it, and repeat the process until it doesn’t.

How long does it take to get air bubbles out of power steering?

Getting air out of the power steering system can take from a few minutes to an hour or more, depending on the method and vehicle complexity. For most cars, turning the steering wheel lock-to-lock multiple times with the engine running and the fluid reservoir full will remove air in about 2-5 minutes. A thorough process with a vacuum pump may take longer, especially for systems with intricate components. 
Quick Bleeding Method (2-5 minutes)

1. Fill: the power steering reservoir to the proper level. 
2. Start: the engine and let it run at idle. 
3. Raise: the front wheels off the ground so they can turn freely. 
4. Turn: the steering wheel slowly from full left to full right and back, several times. 
5. Check: the fluid level and add fluid if it drops. 
6. Repeat: the lock-to-lock turns until fluid foaming or rushing sounds dissipate. 

Vacuum Bleeding Method (Longer Process)
If the quick method doesn’t work, or for intricate systems, a vacuum bleed is more effective. 

1. Apply 15-18 inches of vacuum to the reservoir using a vacuum pump and a modified cap or stopper.
2. With the reservoir under vacuum, turn the steering wheel from lock to lock for about 5 minutes with the engine running.
3. Recheck and top off the fluid level as needed, as it may drop significantly during the vacuum bleeding.

Key Tips

• Watch the fluid: Look for foaming or bubbles in the reservoir, which indicate air is escaping. 
• Check the fluid level: Always keep the reservoir topped off to the proper level. 
• Avoid holding at the stops: When turning the wheel, don’t hold it at the lock for too long, as this can cause the pump to work harder and introduce more air. 
• Consider test drive: After a successful bleed, take the vehicle for a short test drive and recheck the fluid level afterward. 

How do you bleed air out of your power steering system?

And you need to turn the steering wheel all the way from left to right. And when it stops you go again and when you do that. You can see the air coming out and bleeding the system out.

How to get rid of air bubbles in power steering fluid?

To remove air from a power steering system, fill the reservoir, lift the front wheels off the ground, start the engine, and slowly turn the steering wheel from full left to full right about 15-20 times while keeping the fluid topped off. Do not hold the wheel at the stops. Shut off the engine, recheck the fluid level, and repeat the process until the fluid level remains stable and the system is no longer noisy.
 
Tools and Materials

• New power steering fluid
• Jack and jack stands
• Wheel chocks
• Vacuum pump (optional, for stubborn cases)
• Liquid vapor separator (optional)

Step-by-Step Guide

1. Fill the reservoir: With the engine off, fill the power steering reservoir to the correct level. 
2. Lift the vehicle: Use a jack to lift the front of the vehicle, ensuring the front wheels are off the ground. Place jack stands for safety and then position wheel chocks at the rear wheels. 
3. Start the engine: Start the engine and let it idle. 
4. Turn the steering wheel: Slowly turn the steering wheel from the full left position to the full right position and back again, repeating the movement 15 to 20 times. 
5. Check and refill the fluid: As you turn the wheel, the fluid level will drop; add fluid as needed to prevent new air from entering the system. Do not let the level get too low. 
6. Listen for noise: You may hear gurgling sounds as the air is pushed out of the system. 
7. Repeat if necessary: If the system is still making noise or the fluid level continues to fluctuate, repeat the process. 
8. Final check: Once the fluid level is stable and the noises cease, shut off the engine and recheck the fluid level one last time. 

If Air Persists

• Vacuum bleeding: Opens in new tabFor systems with stubborn air, a vacuum pump can be attached to the reservoir to draw air out while the engine idles. 
• Check for leaks: Opens in new tabCheck for any external leaks, as an external leak can introduce air into the system. 

This video demonstrates the process of bleeding air from the power steering system: 57sCARDONE IndustriesYouTube · Nov 21, 2014
Important Considerations

• Safety: Always use jack stands to support the vehicle, never relying solely on a jack. 
• Fluid type: Use the correct type of power steering fluid specified in your vehicle’s owner’s manual to avoid damage. 
• Do not overfill: Overfilling the reservoir can cause fluid to spew out. 
• Avoid holding the wheel at stops: Turning the wheel to the full lock position for extended periods can put excessive strain on the power steering system.