How To Check Power Steering Fluid and When To Change It

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When I first started as an auto technician, power steering fluid (PSF) was an afterthought. Except for leaks, I could count on one hand the number of power steering (PS) system repairs I had to make.

That all changed in the late 1970s. To produce smaller and lighter cars, manufacturers replaced hardened cast iron steering gearboxes with aluminum composite rack-and-pinion steering gears.

Unfortunately, seals directing highly pressurized PSF swelled, cutting grooves into the aluminum housings. After the seals cooled and contracted overnight, PSF leaked through the grooves and past the seals.

When that happened, power steering didn’t work until the heat of the engine swelled the seals to fill the gouges. The aluminum worn away by the seals turned PSF a grayish silvery color and damaged PS pumps.

During the 1980s and ’90s, I repaired or replaced countless steering gears and pumps, and installed PSF filters to capture the metal dust. I also changed or flushed PSF on hundreds of cars. That’s when changing PSF became a scheduled maintenance item.

What Is Power Steering Fluid and What Does It Do?

PSF is a type of synthetic-based hydraulic fluid. The power steering pump pressurizes the PSF when the steering wheel turns. Pressurized PSF allows you to turn the wheel with minimal effort.

To protect the PS system’s internal components from excess wear and tear, PSF contains additives that lubricate, cool, fight corrosion and keep it from foaming and degrading. Low or contaminated PSF makes controlling your vehicle more difficult, especially when slowing or cornering.

Why Should You Check Power Steering Fluid?

Power steering fluid can leak and break down from heat, friction, pressure or component failures. Low PSF levels from an internal or external leak can quickly damage expensive PS system parts. Check to make sure:

  • The fluid level is correct to avoid costly repairs and steering issues.
  • The fluid’s color is clear amber, light brown or reddish. That means it’s free of corrosion-causing moisture, deteriorating rubber or minute metal particles.

How To Check Power Steering Fluid

Pro tip: Whenever working on the PS or any car system, make sure the vehicle is off and on level ground, and the engine is completely cool.

Checking the PSF level is a simple DIY job and should be part of your regular maintenance routine. You’ll need:

  • Clean white paper towels;
  • Disposable gloves;
  • Fluid test strips.

Steps to check PSF level and condition

  • Start the vehicle and slowly turn the steering wheel from side to side one or two times. Shut the engine off.
  • Locate the PS reservoir. Check the owner’s manual for the location and the appropriate type of PSF for your vehicle. Never substitute “universal” PSF for the recommended type.
  • Clean any dirt or grime off the reservoir cap.
  • Carefully remove the reservoir cap, usually a quarter- to half-counterclockwise turn. The cap has a built-in dipstick to measure the PSF level.
  • Clean the dipstick. Reinsert it into the reservoir as far as it will go, then pull it out.
  • Check the PSF level. Depending on the make and model, there can be different markings on the dipstick: full or add, min or max, or hot or cold. PSF expands when heated, as do most fluids in our cars.
  • Wipe off the dipstick with a paper towel and check the color.
  • When PSF degrades or becomes contaminated, it turns dark brown or black. When O-rings are failing or you see a silvery sheen, it means internal metal components are failing.
  • The pros use sophisticated testers like a refractometer for checking PSF integrity. You can buy test strips to check for rust and corrosion causing moisture and metal in PSF.
  • If the PSF is clean but low, slowly add new fluid to the appropriate level mark. Do not overfill!
  • Check for leaks.

Do New Cars Have Power Steering Fluid?

It depends. Check your owner’s manual or with a repair shop to confirm if your vehicle uses PSF.

Some newer cars do not need PSF. They use electric fly-by-wire power steering, which controls the steering gear via electrical motors and computers. However, most cars today still use PSF.

How To Change Power Steering Fluid

The easiest way to change PSF is to suck it out of the reservoir with a dedicated turkey baster.

If you have lots of other internal combustion engine equipment — like a lawn mower, snow blower, generator, etc. — consider investing in a fluid change syringe or inexpensive fluid transfer pump.

However, doing this only replaces the PSF in the reservoir. After sucking out the old PSF and adding new fluid, you’ll need to run the engine, turn the steering wheel from side to side, then repeat these steps until the PSF is clear.

The pros use dedicated equipment to thoroughly flush the PS system. Expect to pay between $100 to $150 for this service. But depending on your make and model, you could DIY this task.

When Should You Change Power Steering Fluid?

It depends. Check your owner’s manual to determine if/when your vehicle’s manufacturer recommends flushing the PSF.

The rule of thumb is two years or 24,000 miles. If the PS is whining or groaning, or the steering wheel becomes difficult to turn, let the PSF fluid’s level and color be your guide.

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