How to inspect for brown or black power steering fluid

Inspecting the power steering fluid involves going under the hood and taking a look at the steering fluid reservoir.
If the color on the dipstick under the cap is brown or black, this is a sign that the fluid is contaminated. You cannot reverse fluid contamination in the power steering system, so the fluid will need to be flushed and replaced with new power steering fluid.
To flush the power steering fluid, you will need to drain the old fluid from the pump, lines, and steering rack—not just the reservoir. This ensures that the new fluid receives as little contamination from the old fluid as possible.

How to flush brown or black power steering fluid

To perform a power steering fluid flush, a mechanic will likely follow these steps:
  • Jack the car
  • Remove the catch tray under the power steering system
  • With a drainage pan ready underneath, disconnect a low-pressure line’s power steering hose from the pump
  • Drain the old fluid
  • Add new fluid to the reservoir—check your car’s manufacturing guide for the type of fluid if it is not written on the reservoir cap
  • Turn the car on and keep filling the reservoir to the halfway mark until new fluid appears in the draining pan
  • Turn the car off, reconnect the power steering hose, and top off the reservoir to the indicated line
  • Turn the car on again and move the wheels back and forth until there is no buzzing noise—this is removing air bubbles from the system
You can perform a flush on your own through this method or by attaching a vacuum extractor pump to the reservoir pump’s return line. If you are unfamiliar with the components of the power steering system, it is highly recommended that you have a mechanic do the flush instead.

Common reasons for brown or black power steering fluid

Steering fluid naturally grows darker with age—here are the most common reasons why:
  • The fluid is degrading: Steering fluid works under high amounts of pressure to strengthen the wheels’ turning capabilities. This pressure creates high temperatures that eventually break down the fluid’s chemicals through what’s called electrochemical degradation, which discolors the fluid.
  • Water is causing oxidation: Water sometimes gets trapped in the power steering fluid reservoir leading to oxidation and discoloration in the fluid.
  • Aluminum particles are contaminating the flow: The rack and pinion in the power steering system can shed a fine powder of aluminum as they wear. The fluid can collect this debris as it flows through these components, resulting in sludge.

Signs your power steering fluid needs to be inspected

There are a few signs that the power steering fluid might already be dirty, in which case it should be inspected and possibly flushed.
  • Your wheels screech when turning side to side
  • Your steering wheel feels stiff while turning
  • The wheels are slow to respond while steering
It’s a good practice to inspect your power steering fluid on a regular basis to monitor its levels and color. Your car’s owner manual should recommend how frequently inspections should occur, but the general guideline is to flush the system every 30,000 - 60,000 miles and monitor in between.

How important is inspecting brown or black power steering fluid?

The power steering fluid flows through the steering rack and pinion to apply pressure to a piston that can then turn the wheels with greater strength. Because it circulates through every component of the steering system to do this, contaminated fluid can clog and damage the entire system if left unchecked. It’s therefore extremely important to inspect its health regularly and schedule maintenance as soon as you notice the fluid is brown or black.

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