Surface deterioration and other signs of obvious wear mean the hose is bad from the inside out, but a clean exterior doesn't guarantee you're good to go. Even if your preliminary inspection comes up clean, you should complete a more thorough test. Though you can visually inspect brake hoses yourself, you need a friend to help you check the pressure.
One person should start the car and pump the brake pedal to build up pressure in the system. This is an important step, because pumping the brake simulates how the hoses function when you hit the brakes while you're driving. Then, the second person can inspect each brake hose. As pressure builds, any flaws or damage in the hose will be much easier to detect. A good hose will retain its shape, size and surface appearance. If the hose swells or shows other signs of weakness, it's time to replace them all. Since brake failure can happen suddenly, it's important to replace faulty hoses as soon as possible, before the car is driven again.
Whether you're eager for more in-depth automotive knowledge or simply want to review general concepts, keep reading. The next page has lots more information to help you find everything you need to know about your car's brakes -- and then some.