PLATE 2998122 - Caterpillar

Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.
A visual inspection of the equipment hydraulic system is the first step of the diagnosis of a problem. Lower the blade and lower the ripper to the ground. Stop the engine. Remove the filler cap slowly from the hydraulic tank. If oil comes out of the breather hole, allow time for the tank pressure to lower. Then remove the filler cap. Perform the following inspections.
Measure the oil level.
Check for air in the oil in the tank. Check immediately after you stop the machine. Use a clear container for a sample of the oil. Check for air bubbles in the oil in the container.
Remove the filter elements. Check for particles that are removed from the oil by the filter element. A magnet will separate ferrous particles from nonferrous particles. (Examples are pistons, O-ring seals, etc.)
Inspect all oil lines and inspect fittings for damage and for leaks.