Air in the Power Steering: Symptoms, Risks, and How to Fix It

Air in a hydraulic power-steering system makes the steering noisy, jerky, and heavier, often showing up as whining or groaning from the pump and foamy fluid in the reservoir; left unresolved, it can overheat and damage the pump and rack. In most cases, the fix is to repair the leak that let air in and bleed the system to purge trapped air. Here’s what’s happening, how to recognize it, and what to do next.

What “air in the system” actually means

Hydraulic power steering relies on pressurized fluid to assist your steering effort. When air enters that closed circuit—through a leak, loose fitting, or after service—the fluid becomes aerated (mixed with tiny bubbles). Those bubbles compress under pressure, causing erratic assist and cavitation inside the pump. Cavitation not only makes noise; it erodes metal surfaces and raises fluid temperature, accelerating wear.

Common symptoms you’ll notice

The following signs typically point to air in a hydraulic power-steering system rather than a purely mechanical steering issue.

• Whining, groaning, or moaning noise that rises with engine speed or when you turn the wheel
• Heavier steering effort, especially at parking-lot speeds, or intermittent assist
• Foamy, milky, or bubbling fluid visible in the reservoir
• Vibration or chattering through the steering wheel during turns
• Pump fluid level dropping after drives (often with small leaks) and fluid splatter from the reservoir cap if severely aerated
• Burnt-smell fluid or darkened fluid from overheating

While any single symptom can have multiple causes, a noisy pump combined with foamy fluid is a strong indicator of aeration from air intrusion.

How air gets into power steering

Air always has a path—it enters when parts aren’t sealing or after the system has been opened for service.

• Low fluid level that allows air to be sucked into the pump inlet
• Leaking or loose hose connections, especially on the low-pressure return side
• Cracked or hardened hoses, loose clamps, or a cracked reservoir
• Worn pump shaft seal or O-rings at banjo bolts and fittings
• Internal rack-and-pinion seal leaks drawing air on return
• Improper bleeding after replacing hoses, pump, rack, or fluid
• Wrong or degraded fluid that foams easily under shear

Finding and fixing the leak or sealing fault is essential; bleeding alone won’t last if air continues to enter.

Why it matters: damage and safety risks

Driving with aerated fluid can escalate minor issues into expensive repairs and create safety concerns.

• Pump damage from cavitation and overheating (bearing wear, vane/rotor erosion)
• Accelerated rack-and-pinion seal wear and internal scoring
• Loss or intermittency of power assist, increasing stopping distance in emergency maneuvers
• Fluid overflow from the reservoir when foam expands, creating a fire and slip hazard

The longer the system runs with air, the greater the risk of permanent component damage and sudden assist loss during low-speed turns.

What to do right now

If you suspect air in the system, take these immediate steps to protect components and restore proper steering assist.

• Check fluid level and condition; top up with the exact fluid specified by the manufacturer (PSF or ATF as called for)
• Inspect for leaks around hoses, clamps, reservoir, pump, and rack; tighten or repair as needed
• Avoid holding the wheel at full lock for more than a second—this spikes pressure and heat
• If the fluid is foamy or the pump is screaming, avoid driving and let the vehicle sit to de-aerate before bleeding
• Perform a proper bleed (see steps below) or have a technician do it, especially after any steering repair

These actions can prevent further damage and often restore normal operation if the root cause is minor.

How to bleed a hydraulic power-steering system

Basic driveway bleed (most conventional systems)

This method purges air safely on many vehicles with traditional hydraulic pumps. Always confirm your vehicle’s procedure in the service manual.

1. Safely raise the front wheels off the ground so they can turn freely.
2. With the engine off, fill the reservoir to the correct mark with the specified fluid.
3. Slowly turn the steering wheel from lock to lock 10–20 times without starting the engine, pausing briefly at each end (do not hold against the stop).
4. Check the reservoir. If fluid looks foamy, wait a few minutes for bubbles to dissipate. Top up as needed.
5. Start the engine and let it idle. Slowly turn lock to lock 5–10 more times. Watch the fluid level; keep it within the specified range.
6. Shut off the engine. Recheck fluid clarity and level. Repeat cycles until no bubbles appear and assist is smooth and quiet.
7. Lower the vehicle, road-test with gentle turns, then recheck level and for any leaks.

If the fluid continues to foam or the noise persists after a thorough bleed, suspect an ongoing air leak, a failing pump, or incorrect fluid.

When a professional bleed is required

Some systems need special equipment or procedures that go beyond DIY methods.

• Electro-hydraulic systems (EHPS) that require scan-tool activation of the pump or bleed routines
• Vehicles that specify vacuum bleeding at the reservoir (20–27 inHg) to remove stubborn trapped air
• After rack replacement, where air pockets can persist without pressure/vacuum cycling

In these cases, a shop can use a vacuum bleeder or factory scan tool to ensure a complete purge and verify pressure/flow are within spec.

Costs and time

A simple top-up and bleed can take 30–60 minutes and cost little beyond fluid. Fixing minor leaks (hose/clamp) typically runs $50–$200 in parts plus labor. A new pump can cost $300–$800 for parts, while rack-and-pinion replacements often range from $800 to $2,000+ installed. Addressing air promptly helps avoid those higher repairs.

Special note on electric power steering (EPS)

Fully electric power steering systems use no hydraulic fluid, so they cannot ingest air. If you have EPS and experience heavy or noisy steering, look for issues like a failing torque sensor, column motor, alignment or tire problems, or low battery/charging voltage. Some vehicles use electro-hydraulic systems, which still have fluid and must be bled.

Prevention tips

Good maintenance reduces the chance of air intrusion and extends component life.

• Check fluid level and condition at each oil change; use only the specified fluid
• Inspect hoses and clamps for seepage or cracking; replace aging rubber proactively
• Avoid turning the wheel against the stop for more than a moment
• Flush fluid at intervals recommended by the manufacturer or when contaminated
• After any steering repair, bleed the system per the factory procedure

These practices keep the system sealed, cool, and properly lubricated, which minimizes noise and wear.

Summary

Air in a hydraulic power-steering system causes noise, foamy fluid, and uneven or heavy steering—and it can quickly damage the pump and rack. Fix any leaks, use the correct fluid, and bleed the system thoroughly; seek professional help for systems requiring vacuum or scan-tool procedures. Don’t ignore persistent noise or froth—addressing aeration early is the cheapest and safest path.

Can you drive with air in power steering?

If there’s air in your car’s power steering system, you’ll notice it becomes difficult to steer and your car may make a growling noise. Driving with air in the system can also cause the steering pump to fail.

What would it look like if I have air in my power steering system?

If you look inside a power steering fluid reservoir. And you notice the power steering fluid looks irrated.

How do you get air out of power steering?

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. 

Can I drive with bubbles in power steering fluid?

Problems with your vehicle’s power steering fluid can damage its power steering pump and steering gear. That’s why it’s best to avoid driving with foamy power steering fluid.