Operator holds control valves in power position too long, causing relief valve to open.
Return control lever to neutral position when not in use.
Using incorrect oil.
Use oil recommended by manufacturer. Be sure oil viscosity is correct.
Low oil level.
Fill reservoir. Look for leaks.
Drain and refill with clean oil. Look for source of contamination and replace filters.
Engine running too fast.
Reset governor or reduce throttle.
Incorrect relief valve pressure.
Check pressure and clean or replace relief valves.
Internal component oil leakage.
Examine and test valves, cylinders, motors, etc. for external and internal leaks. If wear is abnormal, try to locate cause.
Restriction in pump suction line.
Clean or replace.
Dented, obstructed or undersized oil lines.
Replace defective or undersized oil lines. Remove obstructions.
Oil cooler malfunctioning.
Clean or repair.
Control valve stuck open.
Free all spools so that they return to neutral position.
Heat not radiating properly.
Clean dirt and mud from reservoir, oil lines, coolers, and other components.
Automatic unloading control inoperative (if equipped).