Your power steering fluid is dirtyWhen fresh and healthy, most hydraulic power steering fluid should be a deep red color. However, over time, the fluid can degrade and accumulate contaminants. If it begins to look muddy, bubbly, chunky, or even black, that's a sign that you need to replace the fluid as soon as possible.These changes in appearance occur due to a few reasons. The most innocuous reason for power steering fluid to change colors is, simply, age. Over time, the fluid degrades and breaks down, and it absorbs dirt, dust, and other contaminants that manage to get into the system. Brown or muddy looking power steering fluid on its own isn't usually a cause for great concern, but it does mean you need to replace the fluid as soon as possible. Other colors and conditions are more serious. If your fluid looks milky or foamy, it may be a sign that water is seeping into the system, while shiny metal shavings may indicate deeper problems like a faulty power steering pump. Any time you notice that your power steering fluid is discolored, bubbly, or chunky, you need to flush the system at the bare minimum. Allowing dirty or degraded fluid to continue circulating through the system can cause more serious and more expensive damage. If you notice more severe signs, like metal shavings or foam, or extremely dark colors, you may want to ask your mechanic to perform a deeper inspection of the power steering system.The steering wheel is difficult to turnYour car's hydraulic power steering system works by using pressurized fluid to help you turn the wheel. A lot of parts contribute to that function, including a pump, rotary valve, rack and pinion gear, and the hydraulic fluid itself. If any of those parts malfunction or become damaged, the system won't be able to work properly, and, in some cases, it may cease functioning altogether. As the power steering system loses its ability to pressurize fluid and help you turn the wheel, it will become increasingly difficult for you to steer your car. If the situation progresses far enough, you may completely lose your power steering and be forced to drive the old-fashioned way — using a lot of arm power.Many power steering system problems can cause this issue, and the potential culprits range from inadequate or poor quality fluid to a worn-out drive belt, faulty power steering pump, or a broken rack and pinion gear. In terms of severity, the most minor issues that may cause your steering wheel to become stiff are too little power steering fluid or a worn-out drive/serpentine belt. Those issues are relatively minor and cheap to fix. On the other hand, a busted rack and pinion gear is extremely serious and could cost thousands of dollars to repair. If you experience a stiff steering wheel and your power steering reservoir is full of clean fluid, you should visit a professional repair technician for an inspection immediately.