Common faults of hydraulic station system not holding pressure
Hydraulic pressure station pressure is not insurance system with failure, hydraulic station-initiated cases, is definitely stressful. You said not holding the following situations:
1, case of hydraulic station opened, no pressure. Why pump bad pump pressure is too low pressure reducing valve pressure too low. Generally because the pressure directly into the fuel tanks, and can't afford to build pressure.
2, if you are talking about units closed, actuator not holding pressure. Cause: your no circuits of keeping pressure in hydraulic system; one-way valve is bad if the accumulator, perhaps because the accumulator pressure pressure is not enough. If two sets of valves it is best to do. You can keep this nice set of one-way pressure valve to a group that you don't trust, if it can be solved then buy a valve is. And you say louder, likely causes are: plunger pump is broken, wear a long period use will have a lot of noise; there is your pressure may exceed the rated pressure of the piston pump itself; the accumulator itself no sound, only pressure relief with a loud noise.