PV Series

Contaminated fluid is the leading cause of premature pump and valve failure. Take a fluid sample, identify the contaminant type, replace the filter elements, and run a kidney loop filter until the ISO cleanliness target is met.

Jerky or erratic movement is usually air in the cylinder, a sticking directional control valve, or a pressure-compensator setting that is chasing load fluctuations. Purge air, inspect the valve spool, and verify the compensator setting.

Foamy oil means air is mixing with the fluid. The most common entry points are the pump shaft seal, loose suction line fittings, and a return line that discharges above the fluid surface. Find the air entry point and seal it.

Rod seal leaks are the most common cylinder fault. Depressurize, disassemble, and inspect the rod seal and rod surface. A scored rod or bore requires replating or honing before a new seal will hold.

Pump noise with spongy actuator response and foamy fluid means air is entering the system. Check the suction line fittings, reservoir fluid level, and shaft seal before assuming the pump is worn.

Fluid overheating is most often a failed oil cooler, a blocked cooler passage, or an internal bypass circuit creating excess heat by throttling fluid across a pressure drop without doing work. Check the cooler first.

Pressure loss under load means fluid is bypassing without doing work. Start with the relief valve. If it is set correctly and not stuck, measure pump case drain flow to distinguish a pump bypass fault from an actuator bypass fault.

Slow actuator movement with low system pressure usually means the pump is worn and bypassing internally. Measure case drain flow: if it is more than 10% of rated pump displacement, the pump is at end of life.