Power Steering Pump: What It Does and What Happens When It Fails

What Is a Power Steering Pump?

The power steering pump is a hydraulic pump, driven by the engine's serpentine belt, that pressurises power steering fluid and supplies it to the steering rack. This pressurised fluid assists the rack's movement, dramatically reducing the effort needed to steer — particularly at low speeds and when parking.

Without a functioning pump, your steering becomes manual effort only — much heavier and tiring, especially on larger vehicles or when manoeuvring at low speed.

Note: many newer NZ vehicles use electric power steering (EPS) which doesn't have a hydraulic pump at all. This article applies to vehicles with a hydraulic pump — common on Japanese imports from the 1990s through to the late 2000s, including many Toyota Corollas, Honda CRVs, and Subaru Imprezas.

How Does It Work?

The pump is typically mounted on the front of the engine and driven by the serpentine belt. It:

1. Draws power steering fluid from the reservoir (a small plastic reservoir, usually near the engine front)
2. Pressurises the fluid using internal rotary vanes
3. Sends pressurised fluid to the steering rack via high-pressure hoses
4. Receives low-pressure return fluid from the rack back to the reservoir

The pump runs continuously whenever the engine is running. A flow control valve regulates pressure so the pump doesn't over-pressurise at high RPM.

Signs the Power Steering Pump Is Failing

Groaning or Whining Noise on Full Lock

A moaning or whining noise when turning the wheel to full lock (like parking in a tight space) is the most common symptom of a failing pump. This often indicates low fluid or a weakening pump.

Heavy Steering

If the steering feels noticeably heavier than normal, especially at low speed, the pump may not be generating adequate pressure. This can also be caused by a failing pump belt or a blocked pressure hose.

Steering Fluid Leak

Power steering fluid (usually amber-coloured, similar to automatic transmission fluid) leaking from the pump, high-pressure hose, or rack means the system is losing fluid. Low fluid quickly leads to pump damage. See power steering fluid for more.

Jerky or Inconsistent Steering

If the steering bites or resists at certain angles, the pump may be producing inconsistent pressure.

Fluid Frothing or Foamy Fluid in the Reservoir

Air in the system (from a leak or low fluid) causes the fluid to foam — visible as milky or frothy fluid in the reservoir. Air in the system drastically reduces pump effectiveness.

What Causes Pump Failure?

• Low fluid from a leak — the most common cause; running a pump on low fluid damages the pump vanes rapidly
• Old, degraded fluid — power steering fluid should be changed periodically; old fluid causes internal wear
• Worn drive belt — see serpentine belt
• High mileage wear — pumps typically last 150,000–200,000 km with good maintenance

WoF Relevance

Power steering pump issues can lead to WoF failures through:

• Fluid leaks — hydraulic fluid dripping onto the ground or other components
• Drive belt condition — a frayed or cracked belt driving the pump may be noted
• A vehicle with steering that's genuinely unsafe to operate due to pump failure won't pass

NZ Cost to Replace

Remanufactured pumps are widely available for common Japanese vehicles and are a cost-effective alternative to new OEM parts.

When to Book a Mechanic

• Moaning or groaning when turning the wheel, especially at low speed
• Steering feels heavier than it used to
• Fluid level in the power steering reservoir is dropping
• Oily residue visible near the pump, hoses, or rack

Check the fluid level first — sometimes a simple top-up resolves the noise temporarily, but the underlying leak must still be fixed.

Further Reading

• Find a mechanic near you
• Steering rack: what it does and when it needs replacing
• Serpentine belt: what it drives and when to replace it
• Power steering fluid: what it does and when to change it