[thetractorfan]

This may be a sign of contaminants flowing inside the circuit. The more contaminants = less room for oil which makes more pressure and in the hydraulic world pressure creates heat. The hot oil can cause seals to harden, making them lose their suction, resulting in leaks. This is why you need to changes your oil frequently and change the filter frequently. If your cylinder doesn't move, the barrier that the piston rod is attached to may have worn out.