Standard procedures, inspections, and adjustments
Before working on the pump, clean the outside of the pump.
Caution
Contamination can damage internal components and void your warranty. Take precautions to ensure
system cleanliness when removing and reinstalling system lines.
1. With the prime mover off, thoroughly clean the outside of the pump.
2. If removing the pump, tag each hydraulic line connected to the pump. If hydraulic lines are
disconnected, plug each open port with a clean plug, to ensure that dirt and contamination do not
get into the pump.
3. Ensure the surrounding areas are clean and free of contaminants.
4. Inspect the system for contamination.
5. Visually inspect the hydraulic fluid for signs of system contamination, fluid discoloration, foam in the
fluid, sludge, or small metal particles.
6. If there are signs of contamination in the hydraulic fluid, replace all filters, drain and flush the
hydraulic system, and fill with the correct filtered hydraulic fluid.
7. Flush the lines before replacing the hydraulic fluid.
Adjustments
This section offers instruction on inspection and adjustment of pump components. Read through the
entire related section before beginning a service activity. Refer to Pressure measurement for location of
gauge ports and suggested gauge sizes.
Charge pressure relief valve adjustment
The following procedure explains how to check and adjust the charge pressure relief valve.
Warning
The following procedure may require the vehicle/machine to be disabled (wheels raised off the ground,
work function disconnected, etc.) in order to prevent injury to the technician and bystanders. Take
necessary safety precautions before moving the vehicle/machine.
1. Install a 50 bar [1000 psi] pressure gauge in the pump charge pressure gauge port (M3). Install a 10
bar [100 psi] gauge to measure case pressure (tee into L1 or L2 or use servo gauge port M4 or M5).
Operate the system with the pump in neutral (zero displacement) when measuring pump charge
pressure.
Service Manual
Series 90 Pumps
Adjustments
28 520L0818 • Rev 0101 • August 2015
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