A vehicle's safe and smooth operation depends as much on fluid quality and levels as it does on the nuts and bolts machinery. The complex design of the power steering system is largely based on the manipulation and pressure of the power steering fluid, and relies on its ability to operate under widely varying conditions. Proper maintenance of any vehicle includes checking the power steering fluid levels at regular intervals and changing when necessary.
Power steering fluid is a lubricant that helps prevent wear of seals and moving parts, as well as reducing squealing and rubbing noises. It is also a working component of the power steering hydraulic system, applying added pressure to the internal mechanisms to help make steering easier. Power steering fluid is designed to work when the car is idling or travelling at high speeds, in below-zero temperatures to triple digit heat.
Power steering is a clear fluid, sometimes with an amber or pink tone. The reservoir of fluid is typically found under the car bonnet on the passenger side, near the wheel well, though the precise location varies between vehicle models. Newer cars have an opaque reservoir that makes it easy to check the fluid levels. The cap for the reservoir will be marked with the word "steering," or a representative image of a steering wheel. In the Nissan Altima pictured here, the power steering fluid reservoir is up against the wheel well, located behind both the windshield washer fluid and antifreeze reservoirs.
The ingredients of power steering fluid vary between manufacturers. According to the CDC, the most common bases for automotive hydraulic fluids are mineral oil, organophosphate ester, or polyalphaolefin (see Resources). Other esters may be added, along with glycols, corrosion inhibitors and/or silicones. Some auto manufacturers use transmission fluid in their power steering systems, while others have developed long-lasting, vehicle specific steering fluid to last up to 100,000 miles.
If you have any difficulty steering or hear noises when you turn the wheel, check the power steering fluid level. The power steering fluid reservoir is labelled with fill lines for "hot" or "cold", so check that the level matches the appropriate engine temperature. Add fluid if it is low, and inspect the system for leaks. If the fluid is darker than normal, it needs to be changed. Dark brown or black fluid indicates a more serious problem; consult a qualified automotive service technician. Follow the vehicle manufacturer's guidelines on when to change the power steering fluid. If no schedule is given, Automedia.com recommends following the same check/change intervals as the engine coolant (see Resources). If you are changing the fluid yourself, consult a service manual for the individual instructions for your vehicle type.
As noted on Cars.com Car Talk, the seals and other components of the power steering break down over time and contaminate the power steering fluid. This debris can strain or clog the power steering pump and cause it to burn out. Leaks in the system are also dangerous. Without power steering fluid, the power steering system will fail and make turning the wheel extremely difficult, a dangerous hazard while driving. Dispose of steering fluid at the appropriate household hazardous material collection location. Never wash down drains or dump into regular garbage. Follow all manufacturer's guidelines and warnings. Some power steering fluids will burn if ignited. The CDC warns that power steering fluid is harmful if swallowed, and long-term skin exposure can have risks (see Resources).