XLB-4725A
4-6
4-4 HYDRAULIC SYSTEM
Hydraulic system maintenance varies with equipment use and the environment in which
the boom lift is used. Constant attention to keep the oil clean and the reservoir properly
filled will help prevent possible damage to the system. Hydraulic diagrams are provided
at the end of this section for general reference.
Hydraulic System Inspection
Check the hydraulic hose and fittings for leaks and damage daily. Tighten or replace as
necessary to prevent hydraulic oil loss.
Fluid Check and Replacement
The oil level sight gage should be checked with the boom down and the trailer on a level
surface. The reservoir is originally filled with Energol HLP-HD46, a high-grade, non-
foaming hydraulic oil designed for temperatures as low as -20°F (-33°C).
Use Dextron Automatic Transmission Fluid Type A for low temperatures reaching -40°F
(-40°C). If either oil is not available, a good grade SAE 10W hydraulic oil may be used
where the low temperature is above 32°F (0°C). SAE 5W hydraulic oil may be used
where low temperatures reaching 0°F (-18°C).
Do not mix hydraulic oils. Clean the reservoir sump strainer and replace the hydraulic oil
once a year or whenever the oil becomes contaminated.
Air Bleeding
Delayed response or sporadic boom lift motions may indicate air in the lift cylinders. Use
the following procedure to bleed entrapped air from the hydraulic system.
1. Fill the reservoir with the proper hydraulic fluid. Replace, but do not tighten the
reservoir fill cap.
2. Fully raise and lower the boom to return oil with entrapped air to the reservoir.
3. Allow several minutes for air to escape the reservoir oil.
4. Repeat steps 1 through 3 as needed. Add oil slowly and only when the boom is
lowered to prevent adding more air to the system.
