Summarize this article:

Hydraulic hoses have a shelf life, so manufacturers usually print the date of manufacture on the hose. If you use the hose regularly, replace it after 4 to 5 years of use, even if it doesn't show signs of damage. If you use the hose less, it can last up to 10 years. Even if a hydraulic hose hasn't been used much, replace it after 10 years. Rubber degrades over time and the hose could burst due to age. Stress, heat, sunlight, and normal wear and tear all degrade hydraulic hoses. Check the surface of your hose units to see what sort of shape they're in. If you see cracking or tearing, replace this hose. Signs of wear include cracks, tears, and abrasions. Sometimes the outer rubber is worn away and you can see the support wires inside. Replace a hose that looks like this as soon as possible. Hoses might also be crushed or pinched. These should be replaced as well. If your hose is leaking hydraulic fluid, replace it right away. If your machinery has multiple hoses, locate the one with the leak. First, wipe the hoses down to remove any liquid or oil. Then take a piece of cardboard and rub it along the hose. A wet spot should show up on the cardboard when you pass the leaking point. This hose is the one to replace. There is also a special dye designed to detect leaks in hydraulic pipes. It glows when under a black light, making leaks easy to spot. This method is used in industrial equipment and factories. If you want to try this method, get a bottle of hydraulic dye and inject it into your hydraulic system. Then shine a black light around the hose to find the leak.
Replace hydraulic hoses 5 years after the printed date of manufacture. Inspect your hose for signs of wear or cracking. Rub cardboard over the hose to find an oil leak.